Losing weight without losing muscle – Knowledge

1. Why this article?

People who lose weight do not only lose fat.

That is the whole reason for this article. Every loss of weight – whether through eating less, through surgery on the stomach, or through one of the new weight-loss injections – also takes away something the body could well do with: muscle. In the studies this amounts to roughly a fifth to a third of the weight lost, depending on the approach [1][5].

That is not bad in every case, and part of it is even as it should be – why, is explained in section 2.2. But it can be shaped. And that is precisely where our role lies.

Let us say straight away what we are not. We are not dietitians or nutritionists. We do not draw up diet plans, we do not count calories, we do not prescribe medication and we do not judge whether someone should lose weight. That belongs to your family doctor, to a nutrition service – and where medication is involved, unavoidably to the doctor who prescribes it.

And let us say just as clearly what we are. We are the professionals for making sure that what you lose is as much fat and as little muscle as possible. There is one means of doing that which works reliably in the research, and that means is training. Not a supplement, not a device, not a course – training, in a particular form and in a particular amount.

What you will find in this article:

• How large the loss of muscle during weight loss actually is – and how to tell whether it is a problem in your case.
• What is different with the weight-loss injections (the GLP-1 medications) compared with an ordinary diet, what the studies really say, and what is still open.
• The five levers that keep the loss small – ordered by how much they contribute.
• What training achieves in numbers: strength training, endurance training, both combined.
• Where you can train – physiotherapy, medical training therapy, gym, at home – and what speaks for and against each.
• What you train with – machines, dumbbells, elastic bands, your own body weight – with the advantages and drawbacks of each.
• A programme people actually keep up, and what to consider when a medication is stopped.

The article is written for people without medical background knowledge. Technical terms appear, because you will meet them – but each is explained the first time it turns up. The numbers in square brackets refer to the reference list at the very bottom, where every statement can be checked.

And the important note first: this article does not replace an examination or medical advice. What your doctor decides for your situation takes precedence.

1.1 Seven words you will need

• Fat-free mass. Everything in the body except fat: muscle, bone, organs, water. Almost all studies measure this quantity because it is easy to determine with an X-ray scanner. Important: fat-free mass is not the same as muscle – when a study says «1 kilogram of fat-free mass was lost», part of that is water and stored sugar, not muscle tissue.
• Muscle mass. The share of fat-free mass that really is muscle. Measuring it exactly requires magnetic resonance or computed tomography, and few studies do that.
• Energy deficit. You take in less energy than you use. This is the condition for any weight to be lost at all – no matter whether it comes about through food, through movement or through a medication. It is given in kilocalories per day, in everyday speech usually just «calories».
• Strength training. Training against a resistance large enough that you have to stop after a manageable number of repetitions. The word says nothing about where the resistance comes from: machine, dumbbell, band or your own body weight.
• Repetitions in reserve. How many repetitions you could still have managed at the end of a set. Two in reserve means: you could have done two more, the third would have failed. This is the yardstick for effort throughout this article.
• GLP-1 receptor agonists. The technical name for the drug class behind the «weight-loss injections». GLP-1 is a gut hormone that signals fullness to the brain; these medications imitate it. Well-known agents are semaglutide, liraglutide and tirzepatide – the last of these also acts on a second hormone.
• Sarcopenic obesity. Literally: muscle weakness alongside obesity. A state in which someone has a lot of fat and too little functioning muscle – often invisible from the outside, because the weight is high (section 2.4).

2. What is actually lost when you lose weight

2.1 The basic figure: a fifth to a third

A systematic review pooled 26 groups from diet and behavioural programmes and 29 groups after stomach surgery, and calculated for each what share of the weight lost was fat-free mass [1]. The values scatter considerably, but the order of magnitude is stable: a fifth to a third of the weight lost is not fat.

That review also examined what the share depends on. Three things emerged, and all three are usable in practice:

• The stricter the calorie deficit, the larger the share of fat-free mass. Losing weight fast means losing proportionally more muscle than losing it slowly.
• Exercise lowers the share. In the randomised comparisons within this review, training meant that a smaller part of the weight lost consisted of fat-free mass.
• The type of procedure matters. After the more radically rearranging stomach operations the share was larger than after a simple gastric band.

A second point comes from a review of the early phase of weight loss [2]: at the beginning the share is particularly high. In the first days and weeks the body loses water and stored sugar; both count as fat-free mass and neither is muscle. Anyone who consults a body-composition scale after two weeks and takes fright is mostly measuring water. Such measurements only become meaningful after months.

2.2 Why part of this loss is normal and even right

It is worth pausing here, because this point is missing from many newspaper articles.

A person weighing 120 kilograms has more muscle than a person weighing 70 kilograms. That is not a guess but the consequence of a simple fact: someone carrying an extra thirty kilograms trains their legs with every rise from a chair and every step upstairs. The body builds muscle to match the load it has to move.

If the load disappears, part of that muscle is no longer needed. That it is then broken down is not a malfunction but housekeeping: muscle tissue is expensive to maintain, and the body keeps nothing in reserve that it does not use.

The same applies to the other components of fat-free mass. A large study in mice and humans showed that during weight loss with GLP-1 medications the liver loses proportionally more mass than the muscle does [12] – and a shrunken fatty liver is a desired result, not damage.

The decisive question is therefore not «how much muscle was lost?» but: «is enough left – and does it work?» That is exactly what the rest of this article is about.

2.3 When the loss really does become a problem

There are situations in which the loss of muscle no longer falls into the category «appropriate». They can be named:

• When there was little to lose. Anyone who already had little muscle before losing weight – common in older age and after a long illness – has no reserve to subtract from.
• When it happens very fast. The larger the calorie deficit, the larger the share of fat-free mass in the loss [1]. In this respect, rapid weight loss is always the less favourable route.
• When there is no training. The figures follow in section 5. In advance: this is the single largest difference.
• When the weight loss is repeated. On regaining weight, fat comes back faster than muscle [38]. Someone going through several cycles can end up at the same weight with less muscle and more fat than at the start.
• When function declines. This is the most honest sign. If rising from a chair is harder than it was three months ago, that is a finding – no matter what the scales say.

And the reverse belongs here too: in a 45-year-old with marked obesity, healthy joints and two strength sessions a week, muscle loss during weight loss is as a rule not a problem. The benefit of losing the weight clearly outweighs it there.

2.4 Sarcopenic obesity – a lot of fat and too little muscle

For the state that section 2.3 names first there is a technical term and, since 2022, a European definition, worked out jointly by the society for clinical nutrition and the European obesity association [6]. It is called sarcopenic obesity: too much fat mass together with too little – and above all too weak – muscle.

What is remarkable about this definition is its order. It starts not with body composition but with function: muscle strength is tested first, typically grip strength or repeated rising from a chair. Only if that is abnormal is body composition measured at all. Cases are then staged in two levels, depending on whether consequences are already present.

For our work this order is the most important message of the whole document: what counts is not the amount of muscle but what it does. And what it does is also what changes fastest with training.

If you want to read more: the guide on muscle weakness in older age covers sarcopenia in detail, and the article on frailty describes what happens when the reserves as a whole run short.

3. The weight-loss injections: what we know and what we do not

This is the longest and the most careful section of the article, because a great deal is claimed here and little is distinguished.

3.1 What the medications achieve

The effect is undisputed and, in its magnitude, new. In the pivotal trial of semaglutide, participants lost on average 14.9 per cent of their body weight over 68 weeks, against 2.4 per cent in the placebo group [7]. With tirzepatide it was 15.0 to 20.9 per cent over 72 weeks, depending on the dose [8]. For comparison: programmes with dietary change and exercise typically reach 5 to 10 per cent.

That is why these medications have changed the treatment of obesity. Whether they are indicated in an individual case is decided by a doctor – on that we do not comment.

3.2 How much of the loss is fat-free mass?

The best summary of this is a network meta-analysis of 22 randomised trials with 2258 participants [9]. Its findings in four points:

• Across all agents, around 25 per cent of the weight lost was fat-free mass – a quarter.
• The relative share of fat-free mass in the body nevertheless stayed unchanged. That is: the body became smaller, but its composition shifted in favour of fat-free mass, because fat fell more.
• The most potent agents – tirzepatide at the highest dose and semaglutide – produced the greatest loss of weight and fat, but performed worst at preserving fat-free mass.
• Liraglutide was the only agent that produced a meaningful weight loss without a measurable fall in fat-free mass – although its effect on weight is also smaller.

A widely noted commentary by three specialists in nutrition science and obesity research gives a range of 25 to 39 per cent for treatment periods of 36 to 72 weeks [5]. A 2026 review arrives at similar magnitudes and urges particular caution in people who already had little muscle beforehand [10].

And now the context that belongs with it: a quarter to a third – that is roughly the same range as with an ordinary diet (section 2.1). What is special about the medications is not the share but the amount: losing 20 per cent of your weight rather than 7 per cent means losing three times as much fat-free mass at the same share.

3.3 The counterargument: appropriate rather than harmful?

There is a well-founded opposing position, and it belongs in this article because it comes from serious research groups.

A review in a cardiology journal evaluated studies using magnetic resonance imaging – that is, a method that actually pictures the muscle instead of estimating it from an X-ray measurement [11]. Its conclusion: the changes in muscle under these medications are appropriate. Muscle volume decreases to the extent that would be expected given this amount of weight loss, this age and these conditions. At the same time the quality of the muscle improves: fat infiltration within the muscle tissue goes down, insulin sensitivity goes up. Both speak for function rather than against it.

A study published in 2026 that combines four animal experiments with a clinical investigation reached the same conclusion [12]: absolute muscle mass falls slightly, relative muscle mass and relative strength rise, and mobility improves. In the patients studied, body composition improved without strength suffering.

How should these be brought together? Like this: for the majority of those treated, the loss of fat-free mass is probably unproblematic, because it matches the weight lost and function even improves. Two points remain unresolved:

• The subgroup. Both papers point out explicitly that older age and beginning frailty change the picture [11]. Someone with little reserve can afford an «appropriate» loss less well.
• Time. The longest studies run for a good year and a half. But these medications are designed for continuous treatment. What ten years of treatment do to muscle, nobody currently knows.

What nobody disputes, though: those who also train end up better off. The evidence for that is the next section – and it is the actual reason this whole article exists.

3.4 The one study worth knowing

At the University of Copenhagen exactly the question at issue here was investigated: what does exercise add on top of a GLP-1 medication? [15]

How the trial ran. 195 adults with obesity and without diabetes first followed a low-calorie diet for eight weeks and lost an average of 13.1 kilograms. They were then allocated for one year to four groups: exercise programme alone, medication (liraglutide) alone, both combined, or neither.

The result after one year, each compared with the group receiving neither:

Two things stand out. First: the combination beat either measure alone on weight. Second – and this is the more important point: on body-fat percentage the combination was about twice as good as either measure alone, although it was not twice as good on weight. That can only mean one thing: in the combination group, a larger part of the weight lost consisted of fat.

On top of that: only the combination improved long-term blood sugar, insulin sensitivity and cardiorespiratory fitness. The medication alone did not.

3.5 What happens to bone

The same Copenhagen trial was analysed separately for bone density [16], and the result is striking enough to deserve its own section.

Across the whole study the groups lost on average 7.0 kilograms (neither treatment), 11.2 kilograms (exercise), 13.7 kilograms (medication) and 16.9 kilograms (combination). Bone density was measured at hip, spine and forearm.

• In the combination group bone density at hip and spine was unchanged – despite by far the largest weight loss.
• In the medication-only group bone density fell at hip and spine compared with the exercise group – at a similar amount of weight lost.

That last clause is decisive: the difference was not due to different amounts of weight lost but to whether people trained. Bone responds to loading – take weight off it without loading it and it breaks down.

This matters particularly for people whose bone density is low anyway, that is after the menopause and in older age. Anyone with known osteoporosis who is taking a weight-loss medication should discuss it with their treating doctor – and train in the meantime.

3.6 Stopping – and then?

These medications are intended for continuous treatment. In reality they are often stopped: because of side effects, because of cost, because the goal seems reached.

What happens then is well studied. In the extension of the large semaglutide trial, 327 people were remeasured one year after stopping [13]: of the 17.3 per cent previously lost, 11.6 percentage points came back – around two thirds. What remained was 5.6 per cent below the starting weight.

An analysis of 48 studies has described the time course of this regain more precisely [14]: after one year, 60 per cent of the weight lost is back on average; extrapolated, the curve levels off at around 75 per cent. Part of the gain therefore remains – but the larger part goes.

And here it becomes uncomfortable for the muscle. Because fat and muscle do not come back at the same speed. Research on recovery after periods of starvation shows that fat mass is replenished faster than fat-free mass [38]. As long as the body is still missing some fat-free mass it keeps appetite high – and since fat regrows faster, more fat accumulates before the muscle has fully recovered than was there before [37].

So someone who loses weight, loses a lot of muscle in the process and then regains the weight can end up worse off at the same weight than before the whole exercise. That is not an argument against losing weight. It is an argument for keeping the muscle while doing so – and for having a training programme ready for the time after stopping, before stopping rather than after.

3.7 What this means in practice

In summary, if you are taking such a medication or considering one:

• Strength training is part of it, from the outset and not only once something shows up. Twice a week is enough.
• Pay attention to getting enough protein. This is harder on these medications than usual, because appetite is dampened and portions get smaller. With small portions, composition decides.
• Discuss it with the doctor who prescribes it. We are glad to work alongside – but the decision about the medication belongs there.
• Keep the training up when you stop. That is the moment when it counts most (section 9.4).
• Do not judge yourself by the scales alone. What to judge yourself by instead is in section 10.

4. The five levers

What keeps the loss of muscle small – regardless of how the weight comes off? A review devoted to precisely this question names the size of the deficit, the protein supply and training as the levers [4]. We order them here by their effect and add two that belong with them in practice.

4.1 Strength training (the largest)

This is by far the most effective lever, and the figures are in section 5. The core of it in one sentence: in the network analyses, a calorie deficit without training is the only condition under which fat-free mass falls meaningfully [20].

4.2 The pace

The larger the daily calorie deficit, the larger the share of fat-free mass in the loss [1]. There is even a fairly concrete threshold for this: a meta-analysis of strength training under an energy deficit found that above a deficit of about 500 kilocalories per day, no gain in muscle occurred at all [19]. Below that it was possible, above it no longer.

This is not a diet prescription from us – nutrition is not our field. But it is an argument you can raise with your doctor or your nutrition service: one kilogram a week is not twice as good as half a kilogram.

4.3 Protein – important, but not enough on its own

This needs looking at closely, because the studies point in different directions.

What speaks for it. A meta-analysis of 20 randomised trials in people over 50 concluded: those who ate more protein during weight loss retained more fat-free mass and lost more fat [27]. The international expert group on protein supply in older people recommends 1.0 to 1.2 grams per kilogram of body weight per day, more in illness – and expressly more when weight loss and training happen at the same time [29].

What speaks against it. A carefully controlled trial put the question plainly: 61 people with obesity around the age of 63 received 25 per cent less energy for twelve weeks, one half with 1.7 grams of protein per kilogram, the other with 0.9 grams. Ninety per cent of the food was supplied by the university, so little was left to chance [28]. The result: no difference. Both groups lost about the same amount of weight (8.9 versus 9.1 kilograms) and about the same amount of fat-free mass (1.8 versus 2.1 kilograms). Leg strength fell equally in both groups as well.

What these groups did not do was strength training.

Our reading, put as cautiously as the data demand: protein is the building material. Without material nothing happens – but material alone builds nothing. The signal telling the body to keep the muscle comes from training. Do both and you use both; buy only protein powder and you have bought little. On the effect of protein supplements alongside training – on average 0.3 kilograms more fat-free mass across a whole training programme [30] – there is more in the guide building muscle.

In practice this means: a protein source at every main meal. Dairy, eggs, fish, meat, pulses, tofu. And if portions get small on a medication, eat the protein part first. Discuss the exact amount with a nutrition service or your family practice.

4.4 Everyday activity

Not the same as training, but not to be neglected. Endurance activity has little effect on muscle mass (section 5.2) – on keeping the weight off afterwards, a great deal. In the overview by the European obesity association, physical activity is above all what holds the success after the weight loss [22].

The figure most often quoted for this lies between 200 and 300 minutes per week – considerably more than the usual 150 minutes for general health. That sounds like a lot and it is. But it is activity, not sport: brisk walking counts.

4.5 A goal that is not the scales

The fifth lever is not a physical one, and we name it anyway, because in practice it makes the difference.

Anyone who measures themselves solely by weight will, in case of doubt, make the decision that harms the muscle every time: lose faster, eat less, skip the strength training because it does nothing for the scales in the short term. Anyone who also measures themselves by what they can do – stairs, shopping bags, getting up off the floor – makes different decisions. And function is in the end what the weight was supposed to come off for.

5. What training achieves – the numbers

5.1 Strength training during weight loss

Here are the four investigations that convinced us.

First: the simplest figure. A systematic review of 52 studies in people aged 50 and over counted how many groups lost more than 15 per cent of their lost weight as fat-free mass [3]. With a calorie deficit alone it was 81 per cent of the groups. With a calorie deficit plus training it was 39 per cent. In other words: training more than halved the proportion of groups with a marked loss.

Second: the most precise figure. A meta-analysis of six randomised trials in older adults with obesity (strength training three times a week for twelve to twenty-four weeks) compared a calorie deficit alone with a calorie deficit plus strength training [17]:

• Calorie deficit alone: −0.76 kilograms of fat-free mass.
• Calorie deficit plus strength training: −0.05 kilograms – practically unchanged.
• The difference was 0.82 kilograms. Strength training thus prevented 93.5 per cent of the loss.
• And – important for anyone looking for an excuse – fat loss was equally large in both groups (−3.7 versus −3.9 kilograms). So the strength training did not slow the weight loss down.

Third: the broadest figure. A network meta-analysis of 62 randomised trials with 4429 participants compared nine different approaches under a calorie deficit [20]. For preserving fat-free mass a ranking emerged whose bottom place is the revealing part: a calorie deficit without exercise was the only condition with a statistically meaningful loss (−1.66 kilograms against the comparison group). Every form of exercise – from light endurance work to heavy strength training – held the fat-free mass; mixed programmes and moderate-intensity strength training came out best.

Fourth: that it does not hinder weight loss. A meta-analysis of 58 studies in healthy adults found for strength training alone – without any dietary change – a fall in body-fat percentage of 1.46 percentage points, in fat mass of 0.55 kilograms, and in abdominal fat [25]. Small, but in the right direction. A further review in people with obesity across all age groups confirms the pattern: strength training alone builds fat-free mass (+0.8 kilograms), strength training with a calorie deficit holds it [26].

5.2 Endurance training

Endurance training has a different place in weight loss, and it is worth being honest about it.

On weight. Endurance training alone, without dietary change, does little on the scales. A meta-analysis of 116 randomised trials with 6880 participants worked it out precisely: per 30 minutes a week, weight fell by 0.52 kilograms, waist circumference by 0.56 centimetres and body-fat percentage by 0.37 percentage points [23]. Only from about 150 minutes a week at moderate to vigorous intensity did the changes become clinically meaningful. An older meta-analysis arrived at around 1.6 kilograms for isolated endurance training over six months [24]. An overview of twelve systematic reviews covering 149 studies sums up what follows: exercise contributes little to weight loss, but a great deal to body composition and to keeping the weight off [21].

On muscle. Endurance training protects fat-free mass better than nothing, but less well than strength training [20]. Someone who only runs or cycles is doing nothing wrong – but is not using the strongest available lever.

What it is good for. For everything else: heart and circulation, blood pressure, blood sugar, abdominal fat, mood, sleep – and for keeping the weight off afterwards, where it beats strength training. If you have to choose one while losing weight, choose strength training. If you can do both, do both. More on this in the guide endurance training.

5.3 Both combined – the most revealing study

An American trial followed 160 older adults with obesity for six months: all on the same weight-management programme, but with different training – endurance, strength, both, or none [18]. 141 people completed it. Weight loss was the same in all three training groups: 9 per cent. Everything else differed:

Three observations from this:

• Endurance training alone was the least favourable choice for muscle and bone. At the same weight loss, this group lost more than twice as much fat-free mass and six times as much hip bone density as the strength training group.
• Strength training alone protected best, but did little for cardiorespiratory fitness.
• The combination was best at what matters most – physical function, that is, what independence is made of.

For context: these figures concern older adults with obesity on a diet. They must not be transferred to younger people or to training without weight loss. Within their group, however, they are as clear as clinical trials rarely are.

5.4 The uncomfortable truth: you can hardly build

So that expectations are right, this section belongs here.

A meta-analysis examined what strength training still achieves under a sustained energy deficit [19]. Two results that have to be read together:

• The gain in fat-free mass was clearly impaired compared with strength training without an energy deficit. Above a deficit of around 500 kilocalories a day, no gain occurred at all.
• The gain in strength was not impaired. People became just as much stronger, even though the muscle did not grow.

Why is that good? Because strength is what you need in everyday life. Getting up, carrying, climbing stairs, catching yourself when you stumble – these hang on strength, not on size. So during weight loss you can become considerably stronger without a single gram of muscle being added. That is a real improvement and not a consolation prize.

Only the expectation has to be right: anyone hoping for visible muscle gain during a diet will be disappointed. The goal in this phase is to keep. Building comes afterwards.

6. Where to train?

We are asked this more often than anything else – and the answer depends less on the studies than on your situation. The studies are in fact fairly unambiguous: it works anywhere if it is dosed properly. The position stand of the American College of Sports Medicine states explicitly that elastic bands, circuit training and home training also demonstrably increase strength and muscle mass [35].

6.1 Physiotherapy and medical training therapy

Medical training therapy – often abbreviated MTT in Switzerland – is machine-based training under physiotherapeutic supervision, usually on a medical prescription.

In favour:

• The load is adapted to existing complaints. Anyone with knee, hip or back pain – the rule rather than the exception with marked obesity – finds variants here that work without pain.
• The dosage is steered and increased. The commonest reason for a lack of effect is not the wrong exercise but too little effort over too long a time.
• There is somebody watching. Anyone who has never been coached in strength training almost always underestimates how close to the end of a set one may go.
• With a prescription, part of the cost is covered by health insurance.

Against: the number of prescribed sessions is limited. Physiotherapy is therefore rarely the permanent solution but the entry point – and the place where it is settled what you will carry on with independently.

6.2 The gym

In favour: the range of machines and weights, the possibility of progressing over years, fixed opening hours as a structure, and a price that per week is usually low.

Against: the threshold is high for some people – particularly for people with obesity who feel watched. This is not an afterthought: a programme someone avoids out of discomfort has no effect. On top of that, supervision is thin in many places and the introduction ends after two appointments.

If you take this route: look for a place with quiet hours, ask for a thorough introduction, and take along a plan worked out in physiotherapy. We write such plans for people who are not under treatment with us as well.

6.3 At home

In favour: no travel, no waiting, no onlookers, no cost. And the insight that recurs in every study of adherence: the most effective programme is the one that actually happens.

Against: the dosage cannot be raised far. After a few months, your own body weight is often no longer enough for the legs to reach the effective range (section 7.5). And nobody corrects you.

Home training works well when three things are in place: a fixed appointment in the diary, a written programme with weights and repetitions, and at least one way of increasing the resistance – dumbbells, a rucksack full of books, or a set of bands.

6.4 The handover, where it usually fails

The commonest place for a programme to end is the switch from supervised to independent training. So we plan it:

• The programme for afterwards is written during the physiotherapy, not at the end.
• It is carried out at least twice at the new place – in the gym or at home – while the supervision is still running.
• It exists on paper, with weight, repetitions and reserve.
• A check-up appointment after eight to twelve weeks. A single appointment is enough to see whether the load has been increased – and that is almost always where things stall.

7. What to train with? Machines, dumbbells, bands, body weight

7.1 What really counts

The answer first, so that the rest of this section is read correctly: for preserving muscle, the tool is remarkably secondary. What counts is the effort in the individual set – how close to the end you go – and that the load rises over the weeks.

Two direct comparisons show this. A meta-analysis compared elastic bands with conventional resistance and found no difference in strength gains, neither for the arms nor for the legs [33]. A second meta-analysis with 13 studies and 1016 participants compared free weights with machines [34]: no difference in muscle growth; on strength, the group that had trained with the tested tool won each time. Train with the barbell and you get better at the barbell – that is specialisation, not proof of superiority.

The differences between the tools are therefore practical: how easily can you dose? How safe is it? How much space does it need? Those are exactly the questions the next sections address.

7.2 Machines

Advantages. The weight can be read off a pin, which makes progression from week to week traceable – the single most important practical advantage. The movement is guided, so balance plays no part. Setting up is quickly learnt, and even with considerable obesity you can train heavy safely.

Drawbacks. You need a facility. Machines are built for average body dimensions; very tall, very short or very broad people do not always sit well. And balance is not trained along the way – anyone who falls or walks unsteadily needs something else for that.

Particularly suitable for: starting out, heavy loads, people with joint complaints, anyone who wants to progress reliably.

7.3 Free weights: dumbbells

Advantages. Dumbbells are the most versatile tool there is: one pair covers upper body and legs, it fits under the bed, and it costs less as a one-off than three months of gym membership. The movement is not guided, so the stabilising muscles work too. And in older age, lifting dumbbells is one of the few forms of exercise that challenges strength, movement control and balance at the same time.

Drawbacks. The technique has to be learnt. A set of dumbbells at home is too light for the legs after a few months – leg exercises need more resistance than you can comfortably hold in your hands. And when putting them down while fatigued, something can drop.

Particularly suitable for: home, the upper body, older people with guidance, anyone who wants to manage without a facility.

7.4 Elastic bands

Advantages. Cheap, light, space-saving, easy to travel with, and they cannot land on your foot. They allow directions of pull that are awkward with weights – such as rotating the arm outwards for shoulder complaints. For starting out, after injuries and for the shoulder they are often the first choice. And their strength gains are no worse than those from conventional resistance [33].

Drawbacks. Two, and both matter:

• Resistance rises with stretch. A band is tightest where it is pulled furthest – usually at the end of the movement, when the muscle is already shortened. At the start of the movement, where the muscle is long, the resistance is least. That is precisely the opposite of what the muscle would prefer for growth.
• There is a ceiling. Above a certain strength level, even the strongest band is no longer enough to reach the effective range in leg training. And the jump from one band colour to the next is coarse – you cannot represent an increase of two kilograms that way.

Particularly suitable for: the beginning, shoulders and arms, travelling, as a supplement. Less suitable as the sole tool for the legs over months.

7.5 Your own body weight

Advantages. Costs nothing, is always available, needs no introduction. And – a point that counts when losing weight – the exercises are close to everyday life: rising from a chair is rising from a chair.

Drawbacks. Here lies the real catch during weight loss, and it is obvious once said out loud: your body weight is your training weight – and it is currently getting smaller. Someone who starts squatting at 105 kilograms and is still doing the same squats at 88 kilograms is training with 17 kilograms less resistance. The stimulus falls exactly in the phase when it is most needed.

On top of that: for the upper body, your own weight is either too light (wall push-up) or too heavy (pull-up), with little in between. And progressing is awkward – you change levers and angles instead of a number.

Particularly suitable for: starting out, travelling, mobility and balance. Needs a supplement as soon as the weight falls: a rucksack full of books, dumbbells, or switching to one leg.

7.6 The four tools at a glance

7.7 What we recommend

Not a pure form but an order of preference:

• If you can reach a gym: machines as the framework, dumbbells for one or two exercises. That is the simplest route to reliable progression.
• If you stay at home: a pair of adjustable dumbbells as basic equipment, bands for shoulders and arms, body weight for legs and balance. For the legs, plan early for a way to add weight.
• If you have pain: start with whatever is pain-free – usually machines or bands – and widen the selection as things improve.
• In every case: write it down. The tool is secondary, the progression is not. And progression without a record is chance.

8. A programme that lasts

8.1 The framework

Twice a week, about thirty to forty minutes each, five exercises:

• Legs, pushing: leg press, squat, or rising from a chair with weight in the hands. The most important exercise in the whole programme – the thighs carry the largest part of the muscle mass and lose the most during weight loss.
• Back of the thigh and buttocks: leg curl, stiff-legged deadlift or hip raise. These muscles come along in the first exercise but never reach their limit there.
• Upper body, pulling: rowing or lat pull-down. Trains back and elbow flexors at once.
• Upper body, pushing: chest press, bench press, push-up (against the wall or on your knees is fine) or shoulder press.
• Calves, standing.

Why exactly these five? Because together they cover the largest part of the muscle mass, and because a programme somebody keeps up for a year is worth more than one that looks perfect and ends after six weeks.

If you have even less time: the first four exercises, two sets each. That takes twenty minutes.

8.2 The dosage

• How often: twice a week per muscle group. Three times is slightly better; twice is the point at which most of the effect is reached.
• How many sets: two to three per exercise.
• How many repetitions: about six to fifteen. The exact number is not decisive for preserving muscle.
• How heavy: such that two to three repetitions would still have been possible at the end of the set. This is the most important point on the whole list. A set after which you could have managed eight more was a warm-up.
• How to progress: when you reach the upper repetition number with the same reserve, increase the weight next time by the smallest available step.
• Rests: two minutes between sets, three for heavy leg exercises.

Two to three in reserve is deliberately a safety margin. For pure muscle building, going a little closer to the end would be marginally more effective – but someone who is losing weight is more tired than usual, and a programme with a margin is kept up more reliably. There is more detail in the guide strength training.

8.3 The first four weeks

Because the start decides whether it continues:

• Weeks 1 and 2: all five exercises, one set each, deliberately too light. The aim is not the stimulus but getting used to it – and finding out which weights come into question at all. Muscle soreness in this phase is normal and no sign of effectiveness.
• Week 3: two sets per exercise, weight such that about five repetitions remain in reserve.
• Week 4: two to three sets, two to three in reserve. From here it is the programme from section 8.2.

Four weeks to full dosage seems slow. They are the reason somebody is still training a year later.

8.4 When an exercise hurts

With marked obesity, knee, hip and back complaints are common. They are a reason to change the exercise – not to leave it out. The order we work in:

1. Lower the weight, raise the repetitions. For preserving muscle this is barely a loss; for the irritated joint it is a large gain.
2. Adjust the range of movement. Usually only one part hurts. Leaving that part out and using the rest fully is better than stopping – half a squat is infinitely more than none.
3. Change the position. Seated rather than standing, on the machine rather than free, on one leg rather than two.
4. Only then replace it, and then with an exercise that hits the same muscle.

On the pain threshold: with persistent complaints, mild and stable pain during the exercise is often acceptable, as long as it settles within a day and the complaints do not increase over the weeks. With fresh injuries, after operations and where the cause is unclear this does not apply.

9. Special situations

9.1 Older people

Here the balance is a different one, and it deserves care.

On the one hand, losing weight in older age brings real advantages: less load on the joints, better blood sugar, more mobility. On the other hand, the loss of fat-free mass here meets a reserve that is already smaller – and that refills more slowly.

The studies give a clear direction. In older adults with obesity on a diet, strength training prevented almost the entire loss of fat-free mass [17], and the combination of strength and endurance training produced the greatest improvement in physical function – at the same weight loss [18].

For people who already have sarcopenic obesity, a network meta-analysis of 14 trials with 955 participants compared the forms of training [31]. The result differs by goal:

• Multicomponent training – strength, endurance and balance combined – was best for body composition and walking speed. It was the only form that meaningfully increased fat-free mass.
• Pure strength training was best for grip strength and for repeated rising from a chair.

And the classic from 1994 still belongs here, because it shows how much remains possible: in nursing home residents with an average age of 87, muscle strength doubled in ten weeks and the thigh muscle grew measurably [36].

Our recommendation for older people: build the training first, then lower the weight. Someone who has trained for six to eight weeks before the calorie deficit begins enters it from a different starting point. And the pace may be lower here than in younger people.

9.2 With knee and hip osteoarthritis

For this case there is a particularly informative trial: 454 people aged 55 and over with obesity and knee osteoarthritis were followed for eighteen months in three groups – diet, exercise, or both [32].

• Weight loss: diet with exercise 10.6 kilograms (11.4 per cent), diet alone 8.9 kilograms (9.5 per cent), exercise alone 1.8 kilograms (2.0 per cent). Here too: exercise alone does little on the scales.
• Load in the knee joint: clearly lower in the groups that lost weight. Every kilogram less relieves the knee several times over with every step.
• Inflammatory markers in the blood: lower in both diet groups.
• Pain and function: best in the group with both.

The message is the same as everywhere in this article: the weight provides the relief, the training provides the function. Together they are more than separately. More on osteoarthritis itself is in the guides osteoarthritis and hip osteoarthritis.

9.3 After stomach surgery

After the more radically rearranging stomach operations, the share of fat-free mass in the weight lost is larger than after diets and larger than after a simple gastric band [1]. The weight loss is large, it comes fast, and nutrient absorption is altered.

This is therefore the situation with the greatest need for accompanying strength training – and at the same time the one in which it happens least often. Anyone planning or having had such an operation should plan the strength training firmly and take the follow-up on protein intake seriously. Both belong to be agreed with the operating centre.

9.4 Keeping the weight off – and the moment of stopping

For keeping weight off, the relations partly reverse. While losing weight, strength training is the more important part; while keeping it off, it is the daily amount of activity [21][22]. The magnitudes named for this lie between 200 and 300 minutes a week – more than is recommended for general health.

When stopping a GLP-1 medication both come together, and the timing is decisive: the programme has to be in place and running before stopping. Anyone who only starts training when the weight is already returning is fighting against a returning appetite and a regain that averages two thirds of what was lost [13][14]. Whoever has kept the muscle has an easier time of it – not least because a deficit in fat-free mass drives appetite further [37].

10. What you can measure – and what you cannot

What is of little use:

• Body-fat scales and hand-held devices using a current. Their values fluctuate with how much you have drunk and the time of day more than the change you want to measure. During weight loss they are particularly unreliable, because the body's water balance shifts.
• The scales alone. They tell you that there is less of something – never what.
• The mirror. Too dependent on light, on the day and on expectation.

What is of use:

• The training diary. Three entries after every set: weight, repetitions, estimated reserve. If you move the same weights at ten kilograms lighter body weight as you did before, you have clearly gained relative to your body – and that is exactly the aim.
• Repeated rising from a chair. How often can you manage it in thirty seconds without using your hands? This test costs nothing, takes half a minute and measures exactly what counts. Repeat every eight to twelve weeks.
• Grip strength. Used as the first step in the European definition of sarcopenic obesity [6]. We measure it in the practice.
• Waist circumference. During weight loss it moves in the right direction more reliably than weight does, and it needs nothing but a tape measure. Always at the same marked spot, always at the same time of day.
• Everyday questions. How many flights of stairs without a break? How far without a rest? How long on one leg? These answers are not muscle mass – they are what you are training for.

And if only one of them: rising from a chair. If this value stays the same or rises during weight loss, things are going well, no matter what the body-composition scale claims. If it falls, that is a reason to get in touch.

11. Eight misunderstandings

• «Losing weight automatically means losing muscle, and nothing can be done about it.» No. With a calorie deficit alone, an average of 0.76 kilograms of fat-free mass was lost; with strength training, 0.05 kilograms – that is 93.5 per cent less [17].
• «Strength training slows weight loss down, because muscle is heavy.» No. In that same meta-analysis, fat loss was identical in both groups [17]. What differs is the composition of the loss, not its size.
• «For burning fat, endurance training is the right thing.» Only in part. Endurance training alone brings about 0.52 kilograms per 30 minutes a week on the scales [23] – and protects the muscle less well than strength training [18][20].
• «If I eat enough protein I do not need training.» No. In the best-controlled trial on this, almost twice as much protein without training made no difference to fat-free mass and strength [28].
• «On a weight-loss injection, training is pointless – the drug does what it wants anyway.» No. The combination of exercise and medication lowered body-fat percentage twice as much as either alone [15] and preserved the bone density that fell under the medication alone [16].
• «You cannot train properly with bands or body weight.» Yes you can. Bands produce the same strength gains as conventional resistance [33]. The catch is not effectiveness but room to progress (section 7.4).
• «I should lose the weight first and start training afterwards.» Exactly the wrong way round. Training before and during weight loss decides what the loss consists of. Afterwards, nothing about it can be changed.
• «If the scales stand still, nothing is happening.» No. During weight loss you can become considerably stronger without the weight moving at all [19]. Strength is what you need in daily life – not the number.

12. What we actually do – and when to get in touch

What happens in the practice when you come to us with this concern:

• A baseline assessment. Grip strength, rising from a chair, walking speed, balance. That takes twenty minutes and gives a starting value against which everything can later be measured.
• A programme that suits your joints. Not the theoretically best one but the one that can be done with little pain – and that stays open to progression.
• Introduction and checking. Judging the effort in an individual set correctly is the one thing that can hardly be learnt from a sheet of paper.
• Planning what comes after. Gym or home, with a written plan and a check-up appointment (section 6.4).
• Working together. With your family practice, the nutrition service and – where medication is involved – with the prescribing doctor. We do not replace them, we complement them.

Get in touch if:

• You are taking a weight-loss medication or planning stomach surgery and are not yet doing strength training.
• You are over 65 and want or need to lose weight.
• Everyday movements are harder than they were three months ago – getting up, stairs, carrying.
• Joint pain is preventing you from training and you have therefore stopped doing anything at all.
• You have been training for three months and nothing has got stronger. Usually it is the effort, or that the load was never increased – both can be sorted out in a single session.
• You are losing weight unintentionally. That belongs to a doctor first and is something entirely different from the subject of this article.

13. In summary

• Every loss of weight also costs fat-free mass – about a fifth to a third of the weight lost, more with a strict deficit and after stomach surgery [1].
• Part of that is appropriate. A lighter body needs less muscle, and during weight loss with GLP-1 medications the liver loses proportionally more than the muscle [12]. The question is not «how much went?» but «what remains, and does it work?»
• With the weight-loss injections, around 25 per cent of the weight lost is fat-free mass, proportionally more with the most potent agents [9]; other groups give 25 to 39 per cent [5]. The share resembles that of a diet – the amount is larger, because more weight comes off.
• Strength training is the strongest countermeasure. In a meta-analysis it prevented 93.5 per cent of the diet-induced loss of fat-free mass without slowing fat loss [17].
• A calorie deficit without exercise was, in a network analysis of 62 trials, the only condition with a meaningful loss of fat-free mass [20].
• Endurance training alone protects less well. At the same weight loss, the endurance group lost more than twice as much fat-free mass and six times as much bone density as the strength group [18].
• With medication, the combination works best. Exercise plus liraglutide lowered body-fat percentage twice as much as either alone [15] and held the bone density that fell under the medication alone [16].
• Protein is the building material, not the signal. More protein without training made no difference in a controlled trial [28]; with training, a sufficient amount is the precondition [27][29].
• The tool is secondary. Bands, dumbbells, machines and body weight work equally well when the effort is right [33][34][35]. They differ in how well you can dose and progress.
• You can hardly build in a deficit – but you can get stronger. Above roughly 500 kilocalories of deficit a day, muscle gain stops; strength gain does not [19].
• After stopping, two thirds of the weight comes back [13][14] – and fat returns faster than muscle [38]. The programme for afterwards has to be in place beforehand.

The last word belongs to the division of labour. How much weight comes off is decided by nutrition and – where they are indicated – by medications. What that weight consists of is decided by you in the training room. That second question is rarely asked, and yet it is the one that will show, ten years from now, whether losing the weight made you lighter or merely weaker.

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