How to gain weight healthily

There are lots of reasons why someone might like to gain weight. If you've been unwell or receiving treatment for a condition like cancer, it's not uncommon to lose weight, especially if you are unable to eat or you have no appetite. Other people might choose to put on weight for aesthetic reasons, such as someone who goes to the gym and wants to build more muscle.

Whatever your reasons, it's important to ensure that you manage your weight gain healthily.

Energy surplus

Kirsty Barrett, a registered dietician says: "To gain weight you need to create an energy surplus."- take in more energy than you burn off.

Whilst someone who is trying to lose weight through their diet should consume fewer calories than their recommended daily intake - an average of 2,000 kcal for women and 2,500 kcal for men - someone who is trying to gain weight should eat more to get extra energy.

"This can be done by generally just increasing the quantities that you eat but not everyone is able to do this," she explains. "The easiest way to increase energy intake is to increase the fat content of the diet." According to Barrett, fat has nine calories per gram, whereas carbohydrates and protein have four calories per gram.

"Obviously, eating high-fat foods on their own - think oils, butter, spreads and cream - isn't the most palatable, so as dieticians we tend to advise adding these things to meals to increase the calorie content. For example, adding a teaspoon of oil into pasta sauces, adding cream and cheese to soups or adding cream to fruit-based puddings."

However, it's important to continue to eat healthy foods, even if you're adding high-fat foods to your diet. For example, eating fruits, vegetables and wholegrains, which provide nutrients and fibre.

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Muscle or fat?

Some people are medically underweight or need to gain weight for health reasons. Other people of a healthy weight may want to gain weight - to develop a more muscular build, for example. Does this change the way that you should approach weight gain?

"In both of these situations we want to gain muscle," says Barrett. "In the case of those who have been unwell, we likely also want to promote some restoration of body fat as well."

The main difference between dietary changes for these scenarios is the amount of fat that you should be eating. "If I'm advising someone who has been unwell in hospital and has lost weight, I'd focus more on overall energy intake, ideally looking at things that are both high in fat and also high in protein - cheese, full-fat yoghurt, nuts and seeds."

Protein is central to muscle growth. "For someone who is at the gym, the focus would be more on higher-protein foods, often choosing the lower-fat varieties but ensuring their energy intake is enough to support muscle growth. Protein, especially when paired with resistance exercise, promotes muscle synthesis."

Saturated and unsaturated

If you're looking to put on weight, you might be thrilled by the idea of loading up on cakes and pastries. But there is a big difference between saturated and unsaturated fats.

"Health-wise, saturated fats are linked with increased cholesterol levels and therefore an increased risk of cardiovascular disease," says Barrett. "They are generally from animal sources and are solid at room temperature. Unsaturated fats generally reduce your cholesterol levels and are cardioprotective."

It's important not to throw all of the healthy eating rules out the window. Bingeing on foods packed full of saturated fats can increase your risks of health problems, particularly in those who are already at high risk or those who are younger and normal weight.

"The risks would generally be bigger in those with a higher risk of cardiovascular disease," says Barrett. "For example, those who have already had a heart attack or stroke, those with a strong family history of these conditions or those with an already raised cholesterol level."

So how can you increase your calorie intake without endangering your health? "Unsaturated fats and exercise", says Barrett. "Unsaturated fats such as nuts and seeds are good as they contain both protein and fat. Ideally when people want to gain weight, we want them to gain muscle rather than fat. Exercise is crucial in signalling the muscles to build and repair themselves so is key in someone wanting to gain weight."

If you are going to include saturated fats in your diet, go for dairy, she explains. "There is some emerging research that suggests some saturated fats may have a protective effect. This has been found in dairy fats whereby these types of fats actually seem to be protective and reduce the risk of cardiovascular disease, especially the risk of stroke," says Barrett.

"Although it contains saturated fat, dairy is a great way to try to increase weight due to the cardioprotective effect, and also because it is a good source of easily absorbable protein. We would generally promote trying to increase unsaturated fats first line, but, as mentioned, increasing dairy fat may be less problematic than increasing fats from cakes, pastry, meat and so on."

Increasing your intake

Increasing your portion sizes and the amount you eat seems like the simplest way to start gaining weight. However, for some people this might not be possible if they find it difficult to keep food down or to stomach large amounts of food.

For this, Barrett recommends food fortification - increasing the content of nutrients in food.

"Food fortification is a great way to increase energy intake without increasing the volume they have to eat too much," she explains.

Some examples of this might be:

• Adding cream into porridge in the morning.

• Being more liberal with butter on toast.

• Melting butter on to vegetables.

• Topping pasta meals with cheese.

• Making a milky drink.

Nutrients don't just have to come from food either, she says. "We often advise that patients who are trying to gain weight use nourishing fluids such as milk, fruit juices or smoothies to ensure they are also getting some energy from their drinks as well - and they all still count towards fluid intake."

Taste changes

People who lose weight through illness might not be able to enjoy foods that they once loved. People who have gone through cancer treatment may experience taste changes which make certain foods bland or nauseating.

"Taste changes can be really difficult," says Barrett. "Sometimes patients prefer cooler foods such as ice cream or yoghurts. Some prefer stronger flavours, so using lemon or lime, spices, gravies or sauces can be helpful. If someone is struggling with gaining weight after being unwell, they can usually be referred to see a dietician about this via their GP."

Speak to your doctor

If you are planning to make significant changes to your diet, especially if it is for medical reasons, it's a good idea to speak with a doctor or pharmacist so they can ensure that weight gain happens in a controlled and healthy way.