Wendy advises Olympic athletes on how to improve their diet. She is a lead performance nutritionist for the English Institute of Sport and nutritionist for the Great Britain rowing team.
Everyone should aim to eat a healthy, balanced diet, whatever their activity level, as this will provide you with all the nutrients you need.
The following additional advice is for people who are training once per day or more.
Can I eat more when I'm doing lots of exercise?
If you are exercising once or more every day, you will use more energy than if you did little or none. If you are a healthy weight and don't want to lose body fat, you will need to eat more food each day to maintain your weight.
However, you still need to have a balanced diet. To increase your energy intake and fuel your training sessions, eat more carbohydrate-rich foods, such as bread, cereals, rice, pasta and potatoes. Try to choose wholegrain varieties, and eat potatoes with their skins on. Include sources of essential fats from foods such as oily fish, nuts and seeds. You will also need enough protein-rich foods to help repair and build your muscles.
Learn how to have a balanced diet by looking at the Eatwell Guide.
Is it better to eat a diet high in starchy carbohydrates or protein when I'm training?
You will need more carbohydrate and protein if you are training regularly each day. Carbohydrates are the fuel that power your exercise regime.
Carbohydrates, including bread, pasta, rice, potatoes and cereals, are the most important fuel for muscles, and an essential energy source for the brain and central nervous system.
Carbohydrates are stored as glycogen in the muscles and liver. These stores are small, so a regular intake of carbohydrate is necessary to keep them topped up. Low glycogen stores may result in poor performance and increase the risk of injury. For some sports, however, such as weight-making sports, where elite athletes may have to weigh in at a certain weight category (such as boxing), or endurance sports (such as long-distance running), there can be physiological benefits of training with low glycogen stores during certain sessions. These sessions must be carefully planned, due to the potential risks.
Most people will be able to get enough protein from a healthy, varied diet. Good sources of protein include meat, fish, eggs and dairy foods.
Athletes need protein in greater amounts and at regular intervals throughout the day for muscle growth and repair. The proportions of carbohydrate and protein required will vary, depending on the sport, so it's best to seek advice from a qualified professional on your individual requirements.
Learn more by reading our pages on starchy foods and how to have a balanced diet.
How should I time my meals and snacks around exercise?
Once you’ve eaten a meal or snack, allow between one and four hours to pass before you start exercising. Your body needs time to digest. The amount of time will depend on the amount of food you've eaten.
If it's an average meal, eating around two to three hours before you exercise works well. If you have only an hour or so before you exercise, then aim for a meal or snack that is rich in carbohydrate, low in fat and moderate in protein, such as porridge made with low-fat milk or a wholegrain sandwich or bagel with chicken and salad. Too much protein or fat will slow down the movement of foods from the stomach, and will make you feel uncomfortable.
Food and drink also plays a part in recovering effectively from training. Good recovery is crucial to prevent a midweek slump in energy levels, and to aid muscle growth and repair. If you are training more than once a day and you have fewer than eight hours between sessions, aim to have a carbohydrate- and protein-rich food or drink within 30 to 60 minutes of finishing your first session. If you are training less than this, or with more time to recover, just eat as soon as you can afterwards.
Do I need to drink when I exercise?
Dehydration is when the water content in your body falls too low. It can have a major effect on exercise performance. It's important to start any exercise session well hydrated. Aim to do this by drinking water regularly during the course of the day.
The amount you need to drink during exercise depends on the amount you sweat. This varies from person to person and also depends on the intensity and length of time exercising, as well as environmental factors.
Water is usually enough for most forms of exercise up to about an hour. For longer-duration exercise lasting several hours, where energy and fluid needs may be greater, a carbohydrate, electrolyte-containing sports drink may benefit.
For athletes with a heavy training schedule each day, the carbohydrates in a sports drink can help to maintain energy levels, and the electrolytes can help to replace salt lost in sweat.
Learn more from our water and drinks page.
My friend exercises to lose weight, but I exercise to build muscle. Should our diets be different?
Yes. To lose weight or, more specifically, body fat, the amount of energy that you consume has to be less than the amount of energy you burn. You will need a diet and exercise regime that makes this happen.
If you are exercising to lose weight, there are key steps you can take to reduce the energy content in your daily diet. Reduce fat, which is the most concentrated source of energy, as well as your alcohol consumption. Eat fewer sugary foods, such as sweets, chocolates, cakes, biscuits and sugary drinks, and eat regular, but smaller, portions of complex carbohydrate foods, such as wholegrain bread, rice and pasta. Include small amounts of foods with essential fats, such as nuts, seeds and oily fish.
Protein foods – such as chicken, fish, lean red meat and low-fat dairy foods – should be included at each meal time to help maintain muscle mass. Eat lots of a variety of fruit and vegetables. It's also important to control portion sizes.
Learn more from our start losing weight page.
However, to build muscle you need to combine resistance training (also called strength training) with a diet that includes enough energy to enable your body to make muscle, and sufficient and regular amounts of protein.
This energy should come mainly in the form of carbohydrate-rich foods, but don't forget to include foods providing essential fats, such as oily fish, nuts and seeds.
Protein provides the building blocks that help to make muscle. Protein should be included at all mealtimes, particularly before and after a resistance training session. Lower-fat milk or low-fat plain yoghurt (which tends to be higher in protein than standard yoghurt) is a practical, easy way to consume protein after training.
Should I take extra supplements when I'm playing sport?
There are many different supplements on the market. Some of them are based on solid research, but others aren't. Most people won't need to take supplements, and athletes need to consider supplements with extreme caution. In the past, some supplements were found to have been contaminated with banned substances. Find out more in the bodybuilding and sports supplements page.
First, ensure that you have a healthy, balanced diet that suits your sport. Consult a registered dietitian or nutritionist with expertise in sports nutrition. They can assess this and advise you on particular supplements.
You can find these experts on the register of sport and exercise nutritionists on the Sport and Exercise Nutrition Register, or via BDA Sport Dietitians.