Around one in five children is overweight and, according to a recent survey, one in ten children has raised cholesterol levels. "Even when children are young, poor diet and obesity can raise blood pressure and cholesterol levels," says Lyndel Costain, a consultant dietician.

"This raises your risk of high blood pressure and heart disease in adulthood. Other problems, such as arthritis and limited mobility, are also caused by being overweight."

How to defuse: The longer you are obese, the greater the risk of health problems. So the sooner you cut out high-fat and sugary foods, the better. Nutritionists recommend a diet rich in fruit, vegetables and oily fish and at least 30 minutes of exercise a day.