1) Try to reduce the amount of Sugar you eat. For example, things like cereal bars have a lot of sugar in them, so try not to eat too many.
2) Remember, 5-a-day is Vegetables as well, not just fruit. Vegetables are extremely important, and most people don't eat enough green vegetables. I know some don't taste that nice, but they aren't that bad!
3) Don't be scared of Full Fat. Fat gives you energy, and as we need this athletes! A good way of getting enough, is by drinking full fat milk ( It isn't the cause of fat.)
4) Increase the amount of Carbohydrates you eat on training days, or days that you are doing a lot of exercise, and try to eat less on rest days.
5) Have something to Eat Soon After Exercise and training to help your muscles recover. For example I try to have a yoghurt - which has protein and fat!
6) Finally, don't become so strict with food that you are unhappy. You can always have an unhealthy day once in a while- Treat Yourself!
and Finally eat when you are hungry.