Eat Yourself Fitter

Don't Starve Yourself

Cutting kilojoules may help the kilograms drop off, but it can also leave you feeling lethargic and weak, hindering your efforts in the gym. Worse, your body can end up hoarding instead of burning fat. A sudden drop in kilojoules is interpreted by the body as a signal to conserve energy because starvation could be imminent.

The body goes into survival mode and the rate at which it burns energy slows. To compensate for the low kilojoule intake, it starts to break down precious lean-muscle tissue for energy - bad news if you want a sculpted-body look. To lose weight, cut your kilojoule intake by no more than 15%.

Conquer your Carb Fear

Sweets and cakes may sound like a fit girl's no-no but if you work out daily, sweet treats can sit happily on your menu. Eating a high-GI snack, such as a slice of ginger loaf, immediately after your workout will deliver fast-release carbs to your fuel-depleted muscles. That snack will be converted to glycogen (muscle fuel) one-and-a-half times faster than normal. It doesn't matter whether you opt for solid or liquid nutrition; the important thing is to consume the carbs within two hours of exercising. But don't overdo it.

Don't Pile on the Protein

It's tempting to think that a high-protein diet will boost your performance in the gym and make you stronger, but the truth is you need only a little more protein than your non-active friends. Regular exercisers need about 1,2g to 1,4g per kg of body weight daily, depending on their sport and how hard they work out.

(That's 72g to 84g if you weigh 60kg.) Most people get sufficient protein from their daily diet. Two or three daily portions (each the size of a deck of cards) of lean meat, fish, poultry, beans, lentils or dairy products will meet your needs. Serious bodybuilders (who need up to 1,8g of protein per kg of body weight daily) and vegans (who exclude meat and dairy products) may need protein drinks or bars to help make up the shortfall in their diet.

Be a GI Jane

Tuck into a bowl of porridge before your morning workout. Studies found that athletes who ate a low-GI meal (foods that produce a gradual rise in blood sugar levels) two to four hours before exercise were able to keep going for longer than those who ate a high-GI meal.

According to a study at Loughborough University in the UK, runners who ate a low GI meal three hours before exercise burnt more fat than those who ate a high-GI meal with the same amount of carbs. For a healthy, high-powered snack, try fruit with yoghurt, Weetbix with milk or a baked potato with cheese.

Watch the Water

You're probably familiar with the advice to drink lots of water when you're exercising but, following a few cases of hyponatraemia (a dangerous condition caused by drinking too much water) among marathon runners, sports-medicine experts now caution against over hydrating yourself in events lasting more than four hours. Drinking water constantly may dilute your blood, causing sodium levels to fall. Although rare, hyponatraemia is potentially fatal. The American College of Sports Medicine recommends drinking only when you're thirsty. You shouldn't drink so much that you take in more fluid than you lose. Sports drinks are better than water if you're running a marathon - their sodium content will prevent hyponatraemia.

Take a Snack

Whether you exercise early in the day or late in the evening, you need to refuel your muscles within a couple of hours. Skipping a post-workout snack or meal will delay your recovery and leave you feeling sluggish the next day. Provided you don't overeat, these kilojoules will not be turned into fat. After working out, have a drink (water, diluted juice or a sports drink) immediately, then a snack (even if you've worked out after supper) or a light meal within two hours. Try a smoothie, a milkshake, a jacket potato with tuna or cottage cheese or a chicken-and-rice salad. Include this snack in your daily kilojoule total and plan ahead to ensure you have the right sort of foods on hand.

Never Run on Empty

It's a myth that training on an empty stomach will help you shed weight faster. The theory behind it is that your blood-sugar levels are low when you're in a fasting state, which prompts the body to burn fat. The problem is you'll tire sooner, so your total kilojoule burn is likely to be less than if you had eaten a light snack two to four hours before exercise. You'll burn more kilojoules if you eat before you work out. When you don't eat before your workout, many of the reasons for exercising - conditioning, fitness, building muscle and losing weight - go out of the window. That's because your body turns to muscle protein for fuel when it doesn't have enough carbohydrates to burn.

Avoid Goo on the Go

Energy gels (concentrated syrupy carbs designed to slip down your throat when you're on the run) may promise instant energy but they can end up as a mass of goo in your stomach if you don't drink enough water with them. You'll need to swig 350ml of water per 25g sachet. Energy bars and gels are not essential if you exercise for an hour or less.

Having a snack - such as dried fruit or a bagel with peanut butter - an hour or two before you train, as well as being properly hydrated at the start, should sustain you for workouts of up to an hour.

Make Friends with Fat

Extremely low-fat diets won't make you leaner in the long term. There may also be adverse side effects, such as poor vitamin and mineral absorption, and reduced immune responses.

The American Dietetic Association and American College of Sports Medicine recommend that regular exercisers consume 20% to 25% of their daily kilojoules in the form of fat. So, if you eat 9 000kJ a day, you should aim to eat 56g to 69g of fat. Omega-3 fatty acids are beneficial if you exercise, as they boost fat metabolism by lowering the levels of insulin. Eat at least one portion of oily fish a week, or a tablespoon of walnuts, pumpkin seeds or flaxseed oil daily.

Don't Pop Pills

If you regularly work out intensively, you'll need more vitamins and minerals than the RDA, so consider taking a multivitamin supplement. But be wary of other sports supplements: ephedrine-based fat-burners, for example, may contain substances that cause diarrhoea and headaches. A 2001 survey funded by the International Olympic Committee of 634 non-hormonal nutritional supplements found that up to 20% were contaminated with banned substances, including steroids. The British Olympic Association and UK Sport advise athletes not to take any supplements.