The body needs energy from food and drink to work properly and stay healthy. Even when you are resting or sleeping, your body uses energy. The more active you are, the more energy your body will use.
The amount of energy you get from food = energy input
The amount of energy your body uses = energy output
The more food you eat, the larger the input. The more active you are, the bigger the output. The important thing is to keep input and output in balance.
Whatever your lifestyle, make sure that your energy intake balances your energy output. If you eat too little, there will be a negative energy balance. Your food will not provide the energy your body needs. The body will use its fat reserves to provide the extra energy and you may lose weight.
It's natural to gain weight as you grow. But if you eat too much, more than you need for the energy your body is using, there will be a positive energy balance. You will not use up all the food you eat and may put on weight.
Keeping your energy input and output in balance is not easy. Most people are not active enough. So the next time your friends want to watch TV, suggest doing something more energetic. Go for a walk or try out a new sport or dance class. You never know, you may start a new craze!
A healthy balance is also about eating the right amount of the right sort of food. Swap a chocolate bar for a banana, a bag of crisps for a fresh fruit smoothie. You might be surprised how good the healthy options taste.
Everyone's energy balance is different, depending on their age, health and activity level. The more active you are the more food and drink you'll need. Listen to your body - it will usually tell you when it's hungry or thirsty.