What other factors affect our metabolism?

Pregnancy: In the same way that larger people have faster metabolic rates, so do pregnant women, as the body adjusts to both carrying the extra weight and to cater for the needs of the growing baby. Eating for two may be a myth, but more energy is required to help the baby grow and develop.

The menstrual cycle: Basal metabolic rate is lowest a week before ovulation. Researchers at the University of Ohio found that exercising in the 14-day period after ovulation burns more fat than at any other time of the month, pointing to the fact that resting metabolic rate is highest at this point.

The weather: Very hot weather is believed to increase the metabolism slightly as the body works at maintaining an even temperature. The same is true of low temperatures as the body works harder to keep from getting too cold.

Meal frequency: The jury is still out on whether eating several small meals instead of three large ones makes a difference to the metabolism. Some argue that the level of the thyroid hormones that control your metabolic rate begin to drop within hours of your last meal, so eating more regularly keeps those levels high. However, there is research that has found it makes no difference. But this will depend on whether the calorie intake is the same in both cases. If your several small meals are not so small then this will negate the benefits.

Low calorie dieting: Consuming too few calories will result in slowing down your metabolism. Muscle requires a certain amount of calories a day just to maintain itself, so too few calories can result in muscle wastage. Fasting, starvation or malnutrition also slow the metabolism down as the body prepares itself for famine and begins to try to conserve energy. So, as the experts have long advised, going without food may cause you to lose weight in the short term, but as soon as you begin to eat normally again, having a slower metabolic rate will begin to take its toll.

Men versus women: Yes, unfortunately as many of us have long suspected, men do tend to have higher metabolic rates than women. They will usually be 20 to 30 per cent higher than the average woman's. There are some drugs available promising to help boost your metabolic rate. But although legal, they have been associated with unpleasant side effects such as shaky hands, dizziness and sweating, and can raise blood pressure too.

Many people argue that aside from regular exercise, there is no way of changing our metabolic rate; that it is predetermined by factors we have little control over. However, research evidence is available to support many of the claims made.

When it comes to long-term metabolism boosting, the safest and most effective way isto combine frequent moderate exercise with a healthy, balanced diet of fresh fruit and vegetables, whole grains and lean proteins. This is likely to increase metabolic rate by about a third. This of course will depend on factors such as age, muscle mass, and weight.