Training guide
Gaining weight can be as hard for some people as losing it is for others. People differ in how much they move about without noticing, how quickly they feel full and how their bodies store extra food, so the same meals can put weight on one person and not another.
If you're underweight, gaining is about health and strength, not a size. Being underweight can mean you're missing vitamins and minerals, and losing weight without trying can be a sign of illness, so the first section of this guide is about when to see a GP.
After that, it covers how much more to eat (the NHS suggests 300 to 500 extra calories a day), protein, easy calorie-dense foods and drinks, strength training so the gain is muscle rather than mostly fat, and how fast to expect it and how to track it.
Being underweight can mean you're missing vitamins and minerals, and weight loss you can't explain can be a sign of illness. See a GP first if you've lost weight without trying, especially 5 to 10% or more of your weight over 3 to 6 months, or if you use control of food to cope with feelings.
The NHS suggests adults who need to gain weight try about 300 to 500 extra calories a day: smaller meals more often, snacks such as cheese, nuts and yoghurt, and milky drinks between meals rather than before them.
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Without training, extra food is stored mostly as fat. In a trial, men who did strength training while eating more gained mostly lean weight. Two or three full-body strength sessions a week is the place to start.
About 1.6 g of protein per kg of body weight a day is enough for most people who lift, spread over 3 to 5 meals and snacks. Food covers it; a shake is only a convenience.
From the same extra food, identical twins gained anything from about 4 to 13 kg, partly because of their genes, and in another study some people burned off extra food by moving about more without noticing. A few people are naturally thin and find gaining hard: a reason for patience and a GP check, not for eating more and more.
Bigger calorie surpluses mostly add fat, not muscle. Weigh yourself a few mornings a week, check your waist and keep a note of your lifts; the body-fat number on bathroom scales isn't reliable.
Losing weight, or being very light, can be a sign of illness, so these come before any plan.
See a GP if you've lost weight suddenly, lost weight without changing your diet or exercise, or use the control of food to cope with feelings. The NHS says unintentional weight loss can be a sign of stress or a serious illness, so see a GP just in case. Losing 5 to 10% or more of your weight over 3 to 6 months is a main sign of malnutrition.
Losing weight even though you're eating more, with a racing or pounding heart, shaking, sweating or feeling hot, can be an overactive thyroid. See a GP; our hyperthyroidism guide covers exercise while it's treated.
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The NHS lists spending a lot of time worrying about your weight and body shape, eating very little food, exercising too much and having very strict habits or routines around food among the signs of an eating disorder, and says to see a GP as soon as you can. Beat adds exercising to make up for eating, exercising when ill or injured, and feeling guilty or anxious when you can't exercise.
If you're being treated for an eating disorder, follow your treatment team rather than this page: Beat says general exercise advice can be harmful for someone with an eating disorder. Beat's helplines are open 3pm to 8pm on weekdays: England 0808 801 0677, Scotland 0808 801 0432, Wales 0808 801 0433 and Northern Ireland 0808 801 0434. Our eating disorders guide has a US helpline.
A strong drive to be more muscular can be part of an eating disorder, especially in men, Beat says. Worrying a lot about one part of your body can be body dysmorphic disorder, which a GP can help with.
If you're worried about a child's weight or eating, or they've lost weight quickly, see a GP or school nurse. The NHS says not to stop them exercising, because it builds stronger bones and muscles.
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BMI (body mass index) is your weight in kilograms divided by your height in metres squared. A BMI under 18.5 counts as underweight, and NICE (the National Institute for Health and Care Excellence) puts the healthy range at 18.5 to 24.9. NICE says to read BMI with caution in very muscular people and from age 65, when a slightly higher BMI may protect you. Our BMI calculator does the sums.
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The NHS says being underweight can leave you short of vitamins and minerals, which can weaken your immune system and your bones. In a pooled analysis of about 4 million never-smokers without long-term illness, a BMI of 15 to 18.5 went with a higher death rate than a BMI of 20 to 25. That's an association, and some of it may be illness that hadn't been found yet.
Body fat stores energy, makes hormones and helps control hunger, insulin and immunity, and it can stop working well if you have too much or too little of it.
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Gaining well means adding muscle and getting the energy, vitamins and minerals your body needs, not just a bigger number on the scales. Muscle is cheap to keep: at rest it uses about 13 calories per kg a day, so 3 kg of new muscle burns only about 40 more calories a day (our arithmetic).
When 16 adults ate 1,000 extra calories a day for 8 weeks, some started moving about more without trying: fidgeting, standing and walking about. That everyday movement accounted for a 10-fold range in how much fat they stored.
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Identical twins overfed by the same amount gained 4.3 to 13.3 kg, and each pair gained a similar amount. In 1,471 healthy thin people, thinness was about 28% down to genes.
After overeating, people tend to eat less later, which is one way the body resists gaining. If you feel full quickly, the NHS's advice (smaller meals more often, drinks between meals) is aimed at that.
Some people are thin by nature, with normal eating, normal periods and normal hormones, unlike in anorexia. In small studies they had less muscle and higher levels of the hormones that make you feel full, and they gained less than others when given extra food for 2 to 4 weeks. Doctors rule out eating disorders and illness before calling it constitutional thinness, and we found no training trial in this group.
Weight loss can come from stress, depression or anxiety, eating disorders, coeliac disease, inflammatory bowel disease, an overactive thyroid, type 1 diabetes, heart failure, some medicines and sometimes cancer. That's why losing weight without trying needs a GP.
In 25 adults living on a research ward who ate about 950 extra calories a day for 8 weeks without training, fat rose by a similar amount whether the diet was 5%, 15% or 25% protein. Lean tissue rose by about 3 kg only on the two higher-protein diets. It's one trial, in people who weren't training.
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In 73 men who did strength training 4 days a week for 8 weeks, those who also drank a 2,000-calorie supplement each day gained about 3 kg, nearly all of it fat-free mass (which includes water and stored carbohydrate as well as muscle). Once their protein needs were met, the extra energy mattered most.
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One older review (2000) of overfeeding studies suggests that thinner people put on a larger share of lean tissue when they eat more than people with obesity do.
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In 21 trained lifters randomised to eat at their needs, 5% above or 15% above (17 finished), faster weight gain mainly meant more fat. In 39 elite athletes, a guided weight-gain diet added more weight and fat than eating freely, but no more lean mass. The best surplus hasn't been tested.
In a pooled analysis, training while eating less than you need held back lean-mass gains, though strength still rose, and a deficit of about 500 calories a day stopped lean-mass gain.
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In 49 trials with 1,863 people, adding protein to strength training helped muscle and strength a little, and the benefit levelled off at about 1.6 g per kg a day. The International Society of Sports Nutrition (ISSN) says 1.4 to 2.0 g per kg is enough for most active people, and that food can meet it.
In 15 adults, 450 calories a day as fizzy drinks raised weight over 4 weeks, while the same calories as sweets were balanced by eating less at other times. It's a small study, but it fits the NHS's advice to have milky drinks between meals.
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In 18 healthy young adults who ate fast food twice a day and moved little for 4 weeks, liver tests rose above normal in 11 and liver fat more than doubled. In 16 overweight adults, 3 weeks of extra sugar raised liver fat by 27% while weight rose by only 2%. Both studies are small.
Across 43 studies, adding aerobic exercise to strength training didn't reduce muscle growth or maximum strength.
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The NHS suggests adults who need to gain weight could try adding about 300 to 500 calories a day. Our calories calculator shows this range if your BMI is under 18.5. If your weekly average weight hasn't moved after 2 to 3 weeks, add another snack or milky drink a day (our editorial suggestion).
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To fill out with muscle rather than gain for your health, eat at about your needs or a little above, as our build muscle guide explains. Bodybuilding guidance suggests about 10 to 20% above your needs, but bigger surpluses mostly add fat and the best amount hasn't been tested.
The NHS's advice is to add about 300 to 500 calories a day; it doesn't set a rate of gain. A guide used in muscle-building is about 0.25 to 0.5% of your body weight a week (about 0.15 to 0.3 kg a week at 60 kg), but it comes from advice for bodybuilders and hasn't been tested in people who are underweight. If you're under medical care, your dietitian sets the pace.
Eat smaller meals more often, with snacks between them. Have drinks between meals rather than before them, so they don't fill you up.
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The NHS suggests cheese, nuts and seeds, yoghurt and puddings such as rice pudding, high-calorie drinks such as milkshakes, and protein from beans, pulses, fish, eggs and meat, as part of a balanced diet. It says not to rely on chocolate, cakes and sugary drinks. Some easy additions (our suggestions):
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The NHS says exercise can improve your appetite. In 100 frail people aged 72 to 98, only strength training together with a supplement drink raised how much they ate in total; the supplement on its own didn't.
About 1.6 g per kg of body weight a day if you're doing strength training: about 100 g for a 60 kg person (our arithmetic). Our protein calculator works out your range, which runs from 1.6 to 2.2 g per kg.
The ISSN suggests about 20 to 40 g of protein a meal (about 0.25 g per kg), every 3 to 4 hours. Three to five meals and snacks a day covers it.
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Food can meet your needs; a protein shake is a convenience if you struggle to eat enough. Beans and pulses, tofu and soya are protein foods for vegetarians and vegans, and our protein calculator lists how much of each food gives 25 g.
Two or three full-body sessions a week, with a day between. The NHS asks adults for strength work on at least 2 days a week, and the American College of Sports Medicine (ACSM) found strength rose most with at least 2 sessions a week.
In each session, do a squat, a hip hinge (such as a Romanian deadlift), a push, a pull and a carry or core move. Start with a weight you could lift 10 to 12 times, and for the first 2 weeks stop each set with 3 or 4 reps to spare while you learn the moves (our plans' starting point).
Do 2 to 3 sets of about 6 to 12 reps, stopping 2 to 3 reps short of failure. Add reps until every set reaches the top of the range, then add a little weight. Work up to about 10 or more hard sets for each muscle a week (our plans' shared notes); in 15 studies, more weekly sets grew more muscle.
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In typical training studies, men gained about 1.5 kg of muscle and adults over 50 about 1.1 kg. People vary a lot: after the same 12 weeks of arm training, some barely changed and others grew a great deal.
Keep walking or cycling: it doesn't cancel muscle or strength gains, and it counts towards your 150 minutes a week. It does burn energy, so eat a little more to cover it (our suggestion). Sleep 7 to 9 hours; sleep loss cut physical performance by about 7.6% across 69 studies.
Our editorial starting point, built from the plans' shared notes on warming up, starting weights, effort and progression, and the 20-minute strength workout.
Loading the 3D figure…
The movement on the figure: Dumbbell goblet squat
Pick a squat, a hinge, a push, a pull and a carry for each session. Each move's guide shows the technique, and the workouts below give the sets and reps.
3D demoDumbbell goblet squatIntermediate · A dumbbell
3D demoBarbell back squatAdvanced · A barbell
3D demoDumbbell Romanian deadliftIntermediate · A dumbbell
3D demoPush-upIntermediate · No equipment
3D demoDumbbell bench pressIntermediate · A dumbbell + A bench or box
3D demoSupported single-arm dumbbell rowIntermediate · A dumbbell + A bench or box
3D demoLat pulldownBeginner · A cable machine
3D demoStanding overhead pressIntermediate · A barbell + A dumbbell
3D demoFarmer's carryIntermediate · A dumbbell + A kettlebellFull-body sessions for home or the gym. Do two or three a week, alongside your eating.
A 20-minute full-body dumbbell workout: two supersets of squats, rows, Romanian deadlifts and push-ups. Twice a week covers the minimum dose.
20 minBeginner8 movesA dumbbell, A bench or boxA 35-minute full-body strength workout with dumbbells: goblet squats, presses, rows, Romanian deadlifts and carries.
35 minIntermediate9 movesA band, A dumbbellHome dumbbell workout B: reverse lunges, push-ups, bent-over rows, single-leg glute bridges, lateral raises and side planks.
35 minIntermediate11 movesA wall, A dumbbellA beginner full-body gym workout: goblet squats, dumbbell bench press, lat pulldowns, Romanian deadlifts and dead bugs, with sets, reps and rest.
45 minBeginner12 movesCardio machine, A bandBarbell strength workout A: back squats and bench presses in sets of five, plus rows. Workout B (squat, overhead press, deadlift) is a separate session.
40 minBeginner6 movesA band, A barbellAn intermediate no-equipment workout: push-ups, split squats, single-leg bridges, pike push-ups and core work.
30 minIntermediate11 movesNo equipmentA gentle 20-minute beginner home workout with a chair, a wall and a band: sit-to-stands, wall push-ups, band rows, step-ups and dead bugs.
20 minBeginner11 movesA bench or box, A wallEach plan builds the weights up week by week. The teenagers' and seniors' plans start gently.
A 12-week beginner barbell program: squat every session, alternate bench and row with press and deadlift, and add weight each time until it stalls.
3 training days50 minBeginner3 days a weekA beginner gym plan: three full-body sessions a week, alternating workouts A and B, with sets, reps, rest and an 8-week progression.
3 training days45 minBeginner3 days a weekThree full-body home workouts a week with dumbbells or no equipment at all, plus walks and an 8-week plan to keep progressing.
3 training days35 minBeginner4 days a weekA 4-day dumbbell-only plan for home or gym: two upper and two lower days, every set, rep and rest, and how to keep progressing when the dumbbells max out.
4 training days45 minBeginner3 days a weekA 12-week workout plan for 13 to 17 year olds: technique first, then light weights, 2 or 3 sessions a week around sport and school, at home or in a gym.
3 training days40 minBeginner3 days a weekA 12-week exercise plan for over-65s: strength and balance three times a week, short balance sessions and daily walks, based on falls-prevention trials.
3 training days40 minBeginnerIn trials, weight rose by about 3 kg in 8 weeks in men lifting weights with a 2,000-calorie daily supplement, and by 3 to 6.5 kg in 8 weeks of overeating on a research ward without training. From the same surplus, twins gained anything from 4.3 to 13.3 kg over 100 days. Your pace depends on how much more you eat and how your body responds, so nobody can promise a timeline.
Weigh yourself at the same time of day, a few mornings a week, and compare weekly averages (our suggestion). Bathroom scales weigh you accurately, but their body-fat figure can be 2 to 4 kg out, and NICE says those readings shouldn't replace BMI.
Keep your waist below half your height, NICE's healthy waist-to-height ratio. Rising weights and reps show the training is working, and photos in the same light every 4 weeks can help too (our suggestion).
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If you're worried about a teenager's weight, start with a GP or school nurse, and don't stop them exercising. Supervised strength training doesn't affect growth in height or weight, and our teenagers' plan is a safe start. We don't suggest counting calories for children or teenagers unless a professional advises it.
People aged 65 and over are at particular risk of malnutrition, but the NHS says losing weight isn't an inevitable part of ageing. Its first advice is fortified foods high in calories and protein, snacks between meals and nourishing drinks. Adults over 50 gained about 1.1 kg of muscle in training studies, and in frail people in their late 80s, strength training more than doubled strength. Our protein calculator gives higher ranges from 65.
With Crohn's or colitis, cancer, an overactive thyroid, type 1 diabetes or heart failure, weight is part of your care team's plan, so ask them first. Our guides for these conditions cover exercise alongside treatment.
For chest pain that comes on suddenly and doesn't go away, pain that spreads to your arms, neck, jaw, stomach or back, or chest pain with sweating, feeling sick, light-headed or short of breath. Call 999 too if someone faints while exercising. During any session, stop for chest pain or pressure, unusual breathlessness, dizziness or fainting.
For weight loss you can't explain, losing 5 to 10% of your weight over 3 to 6 months, weight loss with a big appetite and a racing heart, or using control of food to cope with feelings: the reasons in "Check with a GP first" above.
See a GP as soon as you can, or call Beat on 0808 801 0677 (England), 3pm to 8pm on weekdays. Our eating disorders guide has the numbers for Scotland, Wales, Northern Ireland and the US.
Calories drive weight gain, but what you eat decides what you gain and how your body copes. The NHS says not to rely on chocolate, cakes and sugary drinks, and in small studies a month of fast food or 3 weeks of extra sugar raised liver fat quickly. Without training, extra food is stored mostly as fat.
People differ: twins on the same surplus gained 4.3 to 13.3 kg, but every pair gained, and some people move about more when they eat more. Muscle burns only about 13 calories per kg a day at rest. A small group of naturally thin people find gaining hard and need a doctor's view.
Fat and muscle are different tissues, so one can't become the other, and muscle doesn't turn to fat if you stop training. They can even change in opposite directions at once: young men training hard on a high-protein diet gained about 1.2 kg of lean mass while losing 4.8 kg of fat in 4 weeks.
Bigger surpluses mainly added fat, not more muscle, in trained lifters and elite athletes, and the best surplus is unknown.
Food can meet your protein needs; a shake is a convenience. In 73 men, a protein-and-carbohydrate shake and a carbohydrate-only shake with the same calories added similar weight: energy mattered most once protein needs were met.
It doesn't reduce muscle or strength gains. Keep it, and eat enough to cover it.
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Eat a little more every day, mostly from nourishing foods, and do strength training two or three times a week so more of the gain is muscle. The NHS suggests smaller meals more often, snacks such as cheese, nuts and yoghurt, and milky drinks between meals. If you've lost weight without trying, see a GP first.
The NHS suggests adults who need to gain weight try adding about 300 to 500 calories a day. Our calories calculator estimates your needs and shows this range if your BMI is under 18.5. If your weight hasn't moved after 2 or 3 weeks, add a little more.
Steadily is better than fast: the NHS suggests adding about 300 to 500 calories a day and doesn't set a rate of gain. A guide used in muscle-building is about 0.25 to 0.5% of your body weight a week, but it hasn't been tested in people who are underweight, and people vary a lot. Bigger surpluses mostly add fat.
People do burn different amounts, mostly through how much they move about, and some store extra food more readily than others. But in an overfeeding study every pair of twins gained weight, so eat more often, use drinks and calorie-dense snacks, and give it time. If you can't gain despite eating more, see a GP.
About 1.6 g per kg of body weight a day is enough for most people who lift; more than that added little in trials. Spread it over 3 to 5 meals and snacks of about 20 to 40 g. Our protein calculator works out your range.
Cheese, nuts and seeds, nut butters, yoghurt and rice pudding, milky drinks and smoothies, eggs, beans and pulses, oily fish and meat. The NHS advises not to rely on chocolate, cakes and sugary drinks.
Eat smaller meals more often, and have drinks between meals rather than before them so they don't fill you up. Exercise can help your appetite too. A lasting loss of appetite with weight loss needs a GP.
Some fat gain is normal and healthy if you're underweight. Strength training with a modest surplus makes most of the gain lean: in one trial, men who lifted while drinking a high-calorie supplement gained about 3 kg, mostly fat-free mass. Bigger surpluses add more fat, not more muscle.
No. Food can meet your protein needs, and a shake is just a convenient way to add calories and protein if you struggle to eat enough.
No. Cardio doesn't reduce muscle or strength gains, and it's good for your heart. Just eat enough to cover it.
If you've lost weight suddenly or without trying, have lost 5 to 10% of your weight over 3 to 6 months, or use control of food to cope with feelings. Also see a GP if you're losing weight despite a bigger appetite, or if you're worried about your eating; Beat's helpline in England is 0808 801 0677.
If you're worried, talk to a GP or school nurse first. Eat regular meals and snacks, and keep exercising: strength training with good supervision is safe and doesn't stunt growth. Our teenagers' workout plan is a good start.
Exercise education, not a personal prescription, and clinical review of these guides is pending. Check with a GP before starting hard training if you have a heart condition, chest pain, dizziness or breathlessness when active, and stop for sharp or increasing pain. Health disclaimer.
