To sustain a healthy weight, you need to balance the amount of food you eat with the energy you need. If you eat fewer calories than your body needs (especially if you are physically active) you will lose weight. If you eat more than you need, your weight will increase. The amount of energy we need differs according to our sex, age, weight and the amount of physical activity we take. For example, a small elderly woman will need less food than a young, active man. If you have been ill or have lost a lot of weight you may not feel like eating and keeping to a well-balanced diet may be difficult. Try to keep eating as much as you can and, if necessary, ask your doctor or dietician for advice.