A Guide to Gaining Weight Safely

Being underweight can be both physically and emotionally challenging. You may find that your self-esteem is affected, and that you often feel tired or lethargic.

People who are underweight can also struggle with a weakened immune system, and there is a risk you could be lacking the nutrients needed to maintain good health.

Gaining weight can be a real struggle for some people. Simply trying to eat more food may leave you feeling bloated and uncomfortable - particularly if you’re used to eating smaller meals - and there is a risk that eating the wrong foods will still leave you lacking important nutrients.

Firstly, if you are worried that you are underweight then you should see a doctor so that they can rule out any medical causes.

There are also several things you can do to gain weight in a healthy and sustainable way. These include:

  • Eating more healthy, high-calorie foods
  • Eating more often
  • Drinking energy-dense smoothies or shakes
  • Tracking your calories

Resistance-based exercise can also help you to gain weight, when coupled with the right diet. In fact, an article published in the Canadian Journal of Applied Physiology indicates a strong link between resistance training and an increase in body mass - particularly when combined with healthier eating habits.

In this article we discuss the five best ways to gain weight. You’ll find information on how to increase your weight healthily and sustainably, including advice tailored to people with different dietary needs.

When to worry

Being slightly underweight isn’t always a problem, but being severely underweight does put you at an increased risk of developing nutrient deficiencies. Over time, these nutrient deficiencies can trigger conditions like osteoporosis or anaemia. They may also result in:

  • An increased risk of illness and infection
  • Low mood
  • Fatigue and exhaustion
  • Slower wound healing
  • Reduced muscle strength

Before you worry too much, it is important to remember that weight loss can occur for a number of reasons. Illness, loss of appetite, or emotional distress can all cause short-term weight loss, which will often correct itself over time.

Certain conditions such as crohn's disease, coeliac disease, eating disorders and hyperthyroidism may also cause you to become underweight though, or prevent you from gaining weight easily.

In some cases, a diet plan and an exercise regime are enough to get things back on track, but more serious malnutrition may require hands-on medical treatment.

Before you make any changes to your diet or lifestyle, you should make sure that you are actually underweight. You can check this by using a BMI calculator.

If you score below 19, you should book an appointment with your doctor. They will be able to rule out common medical causes and talk to you about sustainable ways to gain weight.

Some of the more common strategies for weight gain are detailed below, alongside advice tailored to people with specific dietary needs.

Eat more healthy, high-calorie foods

At a mechanical level, gaining weight is simply a matter of consuming more calories than your body burns for energy.

As long as you're not suffering from a chronic condition such as crohn's disease, boosting your intake will help you to gain more weight, particularly if you stick to high-calorie foods.

Avocado on toast with purple houmous

It’s important that you don’t just start eating more junk food though. Junk food is the term used to refer to pre-prepared or packaged food that has low nutritional value. It is also often high in saturated fats or refined sugars, and while they will help to increase your overall calorie intake, they won’t provide you with the nutrients that your body needs, which can lead to other problems.

Data published by the British Dietetic Association shows that approximately 3 million people are currently malnourished in the UK alone, and a diet that’s high in unhealthy, high-fat or high-sugar foods is understood to be the main culprit.

Unhealthy foods are more likely to make you feel bloated and full as well; reducing the amount of calories and nutrients that you can actually eat in a given setting.

Try to focus on eating more nutrient-dense foods which are both high in calories and contain a good variety of the nutrients that your body needs. This could include:

  • Avocados, which are rich in healthy fats, vitamins & minerals
  • Starchy carbohydrates like potato, buckwheat and quinoa
  • Wholegrain bread and pasta
  • Nuts and nut butters, which provide healthy fats
  • Multigrain cereals or oatmeal
  • Full fat dairy produce, which provides minerals and fats
  • Whole eggs, which are calorie dense and high in protein

Adding more lean protein to your diet can also help you to gain weight. Research published by the National Institutes of Health has linked increased consumption of red meat to cardiovascular disease and certain cancers, so try to focus on eating more chicken or oily fish, such as mackerel, tuna and salmon.

What if I’m a vegetarian or a vegan?

Vegans and vegetarians are more likely to be protein deficient, and studies published in Nutrients have shown a correlation between these diets and a tendency to be underweight. If your diet doesn’t include meat or animal produce, it is important that you find alternative sources of protein. Good options include:

  • Tofu
  • Brown rice
  • Peas
  • Nuts
  • Lentils
  • Chickpeas
  • Spelt and Teff

You can find more information on creating healthy vegan and vegetarian meal plans in our Health A-Z.

What if I suffer from coeliac disease?

If you suffer from coeliac disease, you may have lost weight as a direct consequence of your condition. The best way to address this problem is to focus on eating more lean meat, whole eggs and dairy produce. Increasing the amount of healthy fats in your diet can also help you to gain weight without exposing you to gluten.

You can read more about managing coeliac disease in our Health A-Z.

Eat more often

Knowing that you need to eat more is all well and good, but there's every chance that putting more food on your plate won’t actually help you to gain weight.

People who suffer from low appetite - whether as a result of a long-term illness or emotional distress - often find that they get full quite quickly, and can’t eat a lot of food in a single sitting.

Hand dipping dumpling into dip

If you struggle with this issue, you may find it difficult to increase the amount of nutritious food in your diet.

Eating little and often can help you to combat this issue. Some dieticians recommend trying to eat five or six small meals per day, to ensure that you never get too full and can maintain a healthy appetite.

What about snacking?

Snacking between meals can also help you to gain weight. In fact, a study published in Nutrition Journal shows that eating snacks with a high fat content can trigger chemical processes designed to wake up your appetite, so if you’re struggling to stay hungry then snacking could be the perfect solution.

Almonds in a white bowl

Try to limit yourself to healthy snacks: A 28g handful of almonds will provide you with

  • 161 calories
  • 14 grams of unsaturated fats
  • 6 grams of protein
  • 3.5 grams of fibre

While an equivalent serving of potato chips or crisps provides just:

  • 132 calories
  • 5.9 grams of saturated and unsaturated fat
  • 2.1 grams of protein
  • 1.4 grams of fiber
  • 17.4 grams of carbohydrate

The extra protein, fibre and unsaturated fats make the almonds a much better option, while the lack of nutrients in the chips make this a poor choice of snack.

You can learn more about selecting healthy food choices by downloading Public Health England’s Eatwell Guide.

Consider drinking shakes or smoothies

Drinking your calories may also help to stop you feeling bloated or full. Dieticians sometimes recommend nutrient-dense smoothies if their patients are struggling to eat enough solid food, and they can even be used as a meal substitute if you’re careful to ensure they contain a good balance of healthy nutrients.

Three large smoothies with passionfruit

Here’s a healthy smoothie recipe you can try:

  • Approximately ½ a cup of liquid (water, ice, natural yoghurt or kefir)
  • A banana
  • A handful of berries, or any other fruit you like

You can add whey powder, nut butters or dairy produce to increase the nutrient density of your smoothies, and you can also add a range of fruit and vegetables too - from carrots to spinach or pineapple.

Try to avoid shop-bought smoothies or shakes. Unless they are formulated to provide a good blend of nutrients, they can contain a lot of fruit sugars and other unhealthy ingredients.

You should also take care to limit your consumption to one or two smoothies a day. You can find more information about making healthy smoothies here.

Drink after meals

Drinking before a meal can make you feel bloated and reduce your appetite. To prevent this, try to avoid drinking in the hour before your next meal.

Drinking after meals may also help your body to store the calories that you eat. According to an article published in The Journal of Clinical Endocrinology and Metabolism, there is some evidence to suggest that drinking water can temporarily speed up your metabolism.

An increase in base metabolic rate will encourage your body to burn more calories, and prevent you from gaining weight as fast.

Lemon water with mint

By making sure that you don’t drink before you eat, you can prevent this process from kicking in, and encourage your body to store all of the nutrients that you’ve just eaten.

You can find more information on the importance of staying hydrated here.

Track your calories

Research published in Medicine and Science in Sports & Exercise shows that underestimating or overestimating the amount of food you're eating is common. Research suggests that people trying to gain weight often overestimate the amount of food and nutrient density of their food.

Tracking your calories may help to ensure you’re eating enough to gain weight. There are apps that can help you to track your calories, such as My Fitness Pal and Cron-O-Meter. You could also try keeping a detailed food diary if you’d prefer.

Calorie tracking doesn’t work for everyone though. If you suffer from an eating disorder you may find that calorie trackers are a trigger, and need to be avoided.

If you do decide to track your calories, accuracy is important. Most packaged foods have their nutrient contents printed on the label, and there are several online tools like Verywell Fit’s nutrition calculator that can help you work out the caloric density of home cooked meals.

Tracking your diet using an app that allows you to monitor micronutrients can help to ensure you are getting the right mix of nutrients too - preventing you from accidentally missing out on vital vitamins and minerals.

An article in the New York Times does show that the caloric value listed on labels and calorie trackers can be off by up to 20% though, which means that overreliance on calorie tracking could lead to unpredictable results.

Try resistance training

An article published in the Canadian Journal of Applied Physiology demonstrates a clear link between resistance-based exercise and short-term weight gain.

Resistance training is understood to stimulate weight gain by encouraging muscle growth. It’s also thought to trigger changes in your body chemistry that encourage the uptake and storage of any nutrients consumed immediately after exercise.

Women in an exercise class lifting dumbbells

This means that engaging in resistance-based exercise before eating healthy, high-calorie foods could help to encourage weight gain. Resistance-based exercise doesn't have to involve lifting weights at the gym though.

If you’re shy about working out in front of other people - or prefer to exercise in the comfort of your own home - you’ll be pleased to learn that there are a number of different ways that you can enjoy the benefits of resistance training without hitting the gym.

Diabetes Australia have a good guide to resistance training at home, and this article from Harvard Health also helps to explain the benefits of light resistance training - regardless of age or gender.

Still struggling to gain weight?

These strategies should help you to slowly gain weight - particularly if you try two or more at once, and focus on creating a consistent health regimen.

If you’re struggling to gain weight and you’ve tried the strategies listed here, you should book an appointment with your doctor. There are a number of different health conditions that can prevent you from gaining weight - including hyperthyroidism or crohn’s disease - and it’s important to rule them out as soon as possible.

You can also read more about the medical reasons for unexpected weight loss in our Health A-Z.