Insurance companies consider obesity to mean a weight 20 per cent greater than that considered healthy for one's height. To determine whether your weight is right for your height, find your body mass index (BMI) by dividing your weight in kilograms by the square of your height in metres. If the figure is between 19 and 25, you are normal. Between 25 and 30, you are overweight. Over 30, you are obese; over 40, you are very obese.
In the UK, 16 per cent of women and 13 per cent of men are technically obese, but figures are much higher in the US, where just under a third of the population is classified as obese. In the States, this is defined by a BMI of more than 27.8 for men and 27.3 for women.
While lack of physical exercise and consumption of high-calorie foods are the basic causes, could subtle cultural differences account for the higher US figure? "There is no evidence to suggest Americans are eating more calories, or that they are less active than we are, and the average BMI for people in the US and UK is about the same," says Tim Gill, director of the Post-Graduate Nutrition and Dietetic Centre at the Rowatt Institute in Aberdeen. …