Many people with cancer find there are times when they cannot eat as much as usual, and sometimes they lose weight. There are lots of reasons for this.

Cancer itself, or its treatments, may make you lose your appetite. Some people find that they do not feel hungry, or feel full soon after starting a meal. Other people find that food makes them feel sick or that their treatment makes some foods taste different.

Some types of cancer make your body use up more energy, even if you are not very active. This can make you lose weight even though you may still be eating well.

People who are not eating enough, especially if they are losing weight, need more energy and protein in their diet. If you have often tried to lose weight previously, it can be difficult to change your eating habits when you have cancer. However, if you have cancer and are losing weight you may need to eat differently to try and maintain your weight. Your doctor or dietitian may recommend foods that you would normally think of as unhealthy, but they have good reasons for doing this.

This section shows you how to get more energy and protein without necessarily having to eat more food. Not everyone will be able to put on weight with this building-up diet, but the suggestions should help to slow down, or stop, further weight loss.

A good diet is one that gives you everything you need to keep your body working well. The keys to a good diet are variety and balance. You should try to include everyday foods from each of the food groups.

Carbohydrates Breads, rice, pasta, potatoes, breakfast cereals, cakes, biscuits and sweets contain carbohydrate and also provide energy, fibre, vitamins and minerals. Wholemeal and whole grain varieties are especially high in fibre.

Vitamins, minerals and fibre Fresh fruit and fresh vegetables are good sources of vitamins, minerals and fibre when eaten raw or lightly cooked, or made into juices. If the skins are left on, they contain more vitamins. Dried and frozen fruit and vegetables can also be good sources of vitamins.

Protein Meat, poultry, fish, beans, lentils, nuts, eggs, milk and cheese are protein sources which also provide vitamins, minerals and energy.

Fats Sources of fat include: oil, butter, margarine, fatty meats, oily fish, eggs, cheese, cream, nuts, salad dressing and mayonnaise, full-fat milk, yoghurts and fromage frais. Some of these also provide protein, vitamins and energy.

NB: Make sure that eggs are well-cooked, and use commercial, not home-made mayonnaise. If your immunity is low, avoid live yoghurt, fresh salads and cheeses made from unpasteurised milk, such as Brie and blue-veined cheeses, as these foods can contain harmful bacteria.

Energy

Energy is measured in calories. A calorie is simply a unit of energy and on food packaging is labelled as ‘kcal’ for kilocalories. We all need a certain number of calories each day to give us the energy to live, even if we are not very active: just sitting in a chair we need energy to breathe. If there are too many calories in our diet we put on weight, and if there are too few we use up our body’s stores of energy and lose weight. The amount of energy each person needs each day varies. It depends on how quickly their body uses the energy and their level of activity. An adult man needs approximately 2,500 calories per day and an adult woman approximately 2,000 calories.

Proteins

Proteins make up the basic building blocks of the body. Every part of the body contains protein and we need to eat protein every day to maintain and repair our body tissues. The body must have extra protein, as well as extra energy when we are ill, injured or under stress, to repair any damage.

Vitamins and minerals

Vitamins are essential substances which help our bodies to work normally, but we only need tiny amounts of them. If you are eating even a little of the main foods that contain vitamins, you are probably getting a good enough supply. However, if you are not able to eat well for a long period of time, you may need a multivitamin tablet to top up your body’s stores. Your doctor, dietitian or the pharmacist at your hospital can advise you about these. There is no scientific evidence to prove that taking large amounts of vitamins is helpful. In fact it can be harmful to take excessive amounts of certain vitamins, especially vitamins A and D.

Minerals are substances needed by the body for various functions: such as making bones and teeth; maintaining body fluids and tissues; maintaining healthy nerves; and building necessary chemicals (enzymes).

Some minerals are needed in larger amounts than others, such as calcium, phosphorus, magnesium, sodium, potassium and chlorine. Others are needed in smaller quantities and are called trace minerals, eg iron, zinc, iodine, fluoride, selenium and copper. Despite being needed in smaller amounts, trace minerals are just as important as other minerals. Different foods supply different amounts of minerals. Eating a varied diet will give enough of most minerals. However, if you are not able to eat normally, you may need to talk to your doctor or dietitian about whether or not you need a mineral supplement.

Fluids

The body needs a certain amount of fluid each day in order to work properly. If you don’t feel well it may be difficult to drink enough liquid, but it is important to drink at least 1½ litres of fluid a day (2 pints). This can be drunk as water, fruit juice or squash. Drinks that contain caffeine (such as coffee, tea and some fizzy drinks) may make you dehydrated because they make you produce more urine.