When should meals be eaten if you work out at the gym?

The important thing about eating after exercise is not necessarily when, but what, you eat. If you're exercising regularly, it's important to keep up your energy levels by eating a balanced diet that is rich in starchy foods (such as bread, pasta and rice) and contains:

• lots of fruit and vegetables (aim for at least five portions a day)
• moderate amounts of meat, fish or alternatives, and dairy products
• small amounts of fatty or sugary foods

This kind of diet should give you enough energy to work out effectively and maintain your ideal body weight.

If you take in more energy (calories) than you use up, you will put on weight. So you should try to balance the energy you get from foods with the energy you use during the day and while exercising.

Starchy foods are especially important to replenish the glycogen stores in muscle that provide the energy for us to exercise. Studies have shown that for many people who take part in moderate to vigorous exercise, it can take up to 48 hours to replenish the glycogen. So how soon you eat after exercise won't make a difference. The important thing is to consistently eat a balanced diet so your body has the energy it needs.

How many calories do teenagers need?

Young people need lots of energy and nutrients because they're still growing.

These are estimates of the average amount of energy young people of different ages need. Energy is measured in calories (kcal).

• Boys aged 11 to 14 need about 2,220 calories a day.
• Girls aged 11 to 14 need about 1,845 calories a day.
• Young men aged 15 to 18 need about 2,755 calories a day.
• Young women aged 15 to 18 need about 2,110 calories a day.

But remember these figures are only a guide, and young people might need more or less than these estimates, depending on a number of things, such as how physically active they are.

Young people often have big appetites, so it's important for them to have a healthy balanced diet, rather than filling up on sugary or fatty foods, such as crisps, sweets, cakes, biscuits, and fizzy drinks. These foods tend to be high in calories but contain few nutrients, and they can also reduce appetite for healthier foods.

A healthy balanced diet should include:

• plenty of fruit and vegetables – aim for at least five portions a day of a variety of different types
• meals based on starchy foods, such as bread, pasta, rice and potatoes (ideally brown, wholemeal or wholegrain varieties)
• moderate amounts of milk and dairy products – choose low-fat options where you can
• moderate amounts of foods that are good sources of protein, such as meat, fish, eggs, beans and lentils

How can I find an accredited nutritionist or dietitian?

There are a number of ways you can find a qualified professional to advise you about your diet. You could consult either a dietitian or a nutritionist, depending on the kind of advice you want.

Registered dietitians (RDs) are experts in diet and nutrition, so they can provide advice on all aspects of eating and diet, including special diets for medical conditions. The title 'dietitian' is protected by the Health Professionals Council (HPC). This means that someone can't call themselves a dietitian unless they are suitably qualified and registered with the HPC. Registered dietitians are regulated by the Government. The professional association for dietitians is the British Dietetic Association.

You can contact a registered dietitian through your local hospital or GP surgery. You can also search online for a dietitian at Dietitians Unlimited, which is run by the Freelance Dietitians Group of the British Dietetic Association. The HPC publishes its register online, so you can check on its website to see if a dietitian is registered.

Nutritionists are qualified to provide information about food and healthy eating, but not about special therapeutic diets. The Nutrition Society has a register of nutritionists (R Nutr), associate nutritionists (A Nutr) and public health nutritionists (R PH Nutr). The purpose of this register is to provide a list of nutritionists who have received an approved level of training.

A list of registered nutritionists can be found on the Nutrition Society website.

Can you explain what RDAs and DRVs are?

RDA stands for 'recommended daily amount'. RDAs were originally set by the Department of Health in 1979 to say how much of a certain nutrient was needed by different groups of the population. But RDAs were often used wrongly to assess an individual person's diet.

The Department of Health replaced them with DRVs (dietary reference values) in 1991. DRVs are benchmark intakes of energy and nutrients – they can be used for guidance but shouldn't be seen as exact recommendations. They show the amount of energy or an individual nutrient that a group of people of a certain age range (and sometimes sex) needs for good health.

Although DRVs are given as daily intakes, people often eat quite different foods from one day to the next, and their appetite can change so, in practice, the intakes of energy and nutrients need to be averaged over several days. Also DRVs only apply to healthy people.

DRV is a general term used to cover:

• Estimated average requirement (EAR): This is the average amount of energy or a nutrient needed by a group of people.
• Reference nutrient intake (RNI): The amount of a nutrient that is enough to meet the dietary needs of about 97% of a group of people.
• Lower reference nutrient intake (LRNI): The amount of a nutrient that is enough for a small number of people in a group with the smallest needs. Most people will need more than this.
• Safe intake: This is used when there isn't enough evidence to set an EAR, RNI or LRNI. The safe intake is the amount judged to be enough for almost everyone, but below a level that could have undesirable effects.

A full list of DRVs can be found in the 'Dietary Reference Values for Food Energy and Nutrients for the UK', Department of Health, 1991: Report of the Panel on DRVs of the Committee on the Medical Aspects of Food Policy (COMA). This report can be purchased from The Stationery Office.