Healthy weight gain diet: what to eat and how to do it

Why do I find it so hard to gain weight?

It may look easy from the outside, but in our consultations we often see people who struggle to gain even a single kilogram. There are usually several reasons at once. Genetics play a part, as can a high non-exercise activity energy expenditure: the energy you use moving around, gesturing or standing outside of exercise. A high resting metabolism or feeling full very quickly may also contribute.

Having a naturally slim build is common and is not a health problem if your blood tests are normal, you have energy and you maintain good muscle mass. Unintentional weight loss is different. The international malnutrition consensus includes involuntary loss of more than 5% in six months as one of its criteria, always alongside an assessment of the cause [2]. If this applies to you, do not start by eating more. See your doctor first.

How many extra calories do you need to gain weight?

A weight-gain plan provides slightly more energy than you use, from good-quality foods. A review of muscle gain in people doing strength training recommends a moderate calorie surplus, meaning eating 10–20% more than you use [1]. For most adults, that is around 300 to 500 kcal a day. Going beyond that is unlikely to build more muscle, but may add more fat.

The obstacle is often food volume. If you try to eat more by having huge salads or plain boiled vegetables, the water and fibre fill you up quickly. You may feel heavy and bloated, and leave food on your plate. What helps is increasing calorie density, so each spoonful provides more energy without making the meal larger.

How to enrich the meals you already eat

Enriching the foods you already eat is the easiest way to add energy. It is also what the European clinical nutrition guideline recommends for people who are malnourished or at risk [3]. Start with foods enriched with energy and protein. If that is not enough, your doctor or dietitian-nutritionist can assess whether you need nutritional support.

Three ideas for any kitchen:

• Extra virgin olive oil, added without cooking. Add one or two tablespoons to purées, pulses, toast or rice dishes. Each tablespoon adds around 90 kcal without taking up room in your stomach.
• Chopped nuts or nut butter. Add them to yoghurt, porridge and toast. It is best to grind flax or chia seeds.
• Grated cheese, chopped egg or powdered milk. These increase the protein in a soup or pasta dish without increasing the portion size.

How much protein do you need to gain weight?

To make the weight you gain muscle, you need enough protein. An analysis of 49 trials found that, during strength training, the benefits of eating more protein stop increasing at around 1.6 g per kilogram of body weight per day [4]. For people who are malnourished or at risk, the European guideline calls for at least 1.2 g per kilogram per day [3].

In practice, aim for between 1.2 and 1.5 g per kilogram a day. If you weigh 60 kg, that is 72 to 90 g of protein. You can meet this by including pulses, eggs, dairy, poultry or fish across your meals. Our protein for athletes guide explains how to spread it through the day.

Protein alone is not enough if your total energy intake is too low. Without enough carbohydrates and fats, your body uses that protein as fuel instead of building muscle. That is why rice, pasta, potatoes, oats or wholemeal bread should make up a generous part of your plate.

What can you eat to gain weight without feeling stuffed?

When you feel full quickly, the energy in each bite matters more than the weight of the food. The British guideline on nutrition support includes enriched food and snacks among its measures, before any supplement [5], and spreading food over small meals is a practical way to put this into practice. These are things you can try at home.

Small, frequent meals

Spread what you eat over five or six moderate meals. A smaller plate is easier to finish, and between meals you have time for your appetite to return. If you are not hungry at those times, put them in your calendar like any other appointment. To keep snacks handy, our healthy snacks guide offers homemade alternatives.

Plenty of energy in a small volume

Look for foods that provide energy and nutrients together. Avocado, nuts and nut butters, oily fish, eggs, cheese, full-fat yoghurt, dates and dried apricots give a lot in a small space. Cereals and tubers cooked with a good fat also help, such as rice with olive oil or a baked potato with avocado. If you want to know how to use oil in your cooking, see our olive oil guide.

Raw vegetables take up much more room than cooked ones. If you struggle to finish your plate, sautéed vegetables, soups or an omelette take up less space and still add something. Start with the most energy-dense part of the plate and leave the side dish until last.

Drinks that also contribute

Drinking water or clear broth before and during a meal fills you up too early. Keep drinks for between meals and, when you drink, choose something that adds to your intake, such as whole milk, kefir, vegetable soups enriched with oil and cheese, or a homemade shake. If dairy does not agree with you, calcium-fortified soya drink is a similar option. Sugary soft drinks fill you up and add no nutrients.

What a day could look like

Here is an example to give you an idea. It is not a meal plan tailored to you. If you want a full week with a shopping list, see the weekly menu to gain weight.

• Breakfast. Wholemeal toast with olive oil and tomato, an egg and coffee with whole milk.
• Mid-morning. Kefir with rolled oats and a few dates.
• Lunch. Lentils with rice and vegetables, dressed with olive oil, and bread.
• Afternoon snack. A small cheese sandwich and a banana.
• Dinner. Oven-baked salmon with potatoes and vegetables, and full-fat yoghurt.

That is five moderate meals. None is huge, which makes it easier to get what you need without feeling too full.

Do you need shakes or supplements to gain weight?

In most cases, no. A well-planned diet provides all the energy and nutrients you need to gain weight. Oral nutritional supplements from a pharmacy are a later step, used when enriched food does not meet your needs because of illness or poor appetite [3]. Your doctor or dietitian-nutritionist prescribes these supplements. There is no need to turn to commercial shakes either: they can be made at home with kitchen ingredients.

What goes into a homemade shake to gain weight?

If eating is difficult, a shake goes down easily and is easy to digest because there is nothing to chew. Think of it as an extra meal, not a replacement for a meal. You put it together from four parts, choosing one from each.

• Liquid base. Whole milk, kefir or calcium-fortified soya drink.
• A carbohydrate for body. Ripe banana, fine rolled oats, pitted dates or mango.
• A good fat. One or two tablespoons of peanut, almond or other nut butter, half an avocado or a splash of mild olive oil.
• Protein. Plain Greek yoghurt, blended fresh cheese or silken tofu.

A touch of pure cocoa or cinnamon makes it more appealing without adding sugar. If you have it between meals, it is better mid-morning or mid-afternoon than just before a meal, so that it does not take away your appetite. Depending on the amounts, a shake like this provides between 400 and 600 kcal. Bear in mind that soya, peanuts, almonds and milk are allergens, and that the fibre in oats and seeds thickens the shake and fills you up more than it seems. If you prepare it in advance, keep it in the fridge and drink it the same day.

What if you are underweight? Causes and when to seek advice

Being below what is expected for your height is called underweight. In our guide to underweight, healthy weight, overweight and obesity, we explain what this means and what it does not. Here, what matters is to separate two situations.

The first is having been at the same low weight for years, with no other symptoms. This is what we see in many naturally slim builds, and diet is the main tool. The second is weight that has dropped without you trying. The possible causes are very varied and cannot be found out through diet or a guide like this one, so we cannot tell you what is behind it. If your weight has dropped without you trying, an appointment with your doctor comes before any change to your diet [6].

If being underweight comes with a fear of gaining weight, guilt about eating or behaviours to compensate for what you have eaten, the first step is specialist psychological care, and the eating plan comes afterwards, coordinated with it [7]. In our consultations, when someone arrives underweight, we review what they eat, how their appetite is and what their day looks like, and we work together with their doctor if needed.

How to make the weight you gain muscle

Exercise influences the type of weight you gain. If you eat more and lead a sedentary life, much of the surplus is stored as fat. If you combine it with strength training (weights, machines, resistance bands or your own body weight), your muscles receive the signal to grow. By contrast, doing only long, intense cardio increases energy use without providing that stimulus.

The World Health Organization recommends that adults do muscle-strengthening activities at least two days a week [8]. For muscle gain, two to four sessions a week using exercises that involve several joints, with rest between them, are a good starting point. A review with meta-analysis found that the more weekly sets per muscle group, the greater the gain in muscle mass [9]. That is why it is better to increase the workload gradually, with technique first, instead of starting with a lot of volume.

Have something with carbohydrate and protein in the hours around your workout. In what to eat before and after training you will find ideas. To plan your whole diet around your goal, see our fitness diet guide. If you are losing strength and muscle with age, our sarcopenia guide explains how to address it through food. If you have an injury, a heart condition or joint pain, talk to your doctor before you start training with loads.

What mistakes do we see in consultations?

• Weighing yourself every day and giving up after a week. Your weight fluctuates from one day to the next because of hydration, salt or what you have eaten, and these changes hide real progress. If you weigh yourself, do it no more than once a week, on the same day and at the same time. To track changes, measure your waist and hip circumference or use a belt you wear regularly as a reference.
• Eating a lot one day and very little the next few days. A large meal on Sunday does not make up for skipping your afternoon snack for three days. What matters is what you eat over the week.
• Increasing the amount all at once. Going from three to six meals overnight is filling and tiring, and people give up. Add one meal or one enriching step every few days and let your body get used to it.
• Starting training without eating more. Your energy use goes up and your weight stays the same, or even drops. When you start strength training, your food intake needs to increase too.
• Copying someone else’s plan. What works for a friend or a social media profile depends on their appetite, energy use and training. Yours needs to start from your own schedule and from what suits you.
• Ignoring your emotional relationship with food. If you feel guilty about eating more, fear gaining weight or use behaviours to compensate, this is not simply a metabolism problem. The UK guideline on eating disorders (TCA) calls for prompt referral to a specialist service when an eating disorder is suspected [7]. Specialist psychological care comes first; the eating plan follows and is coordinated with it.

Frequently asked questions

How long does it take to gain weight?

It depends on your starting point, your appetite and how much you train, so we do not give timescales or figures. What we do see is that changes sustained over months work better than short efforts. If you notice no change after a few weeks of following the plan properly, tell your doctor or your dietitian-nutritionist.

Can I gain weight without gaining belly fat?

You cannot choose where what you gain accumulates, because that depends partly on genetics and hormones. What does depend on you is making sure a good part of it is muscle, with enough food, protein spread through the day and strength training [4] [8].

Do pastries and soft drinks work for gaining weight?

They add energy, but they fill you up without providing protein or micronutrients and do not give your muscles what they need. With good-quality foods, you reach the same energy and also build muscle mass.

What should I do if I have suddenly lost my appetite?

A sudden change in appetite, especially if your weight drops at the same time, should be assessed by your doctor before you adjust your plan [6]. In the meantime, small meals and low-volume foods are usually easier to manage.