An article printed in the Time magazine in August 2009 not only claimed that exercise won’t make you thin, but may even make you put on weight. People all over have clapped their hands in glee after reading the article and have cancelled their gym sessions and collapsed on the couch... However, the bad news is that there is a lot of false information in the article.

Dr Julia Goedecke from the Medical Research Council, based at the Sports Science Institute in Cape Town says that the studies quoted in the article have been misinterpreted or are based purely on hypotheses. For example the studies only consider body weight and not body composition and we all know that body fat can in fact drop as lean muscle (and therefore body weight) increases from doing exercise. Also the amount of exercise in the studies quoted was neither controlled or measured and was insufficient to induce weight loss anyway. The subjects were only exercising on average for 30 minutes a day when in fact 60 – 90 minutes of exercise per day is required. Another way of looking at it, is that one needs to expend 500 – 1000 calories per day to lose weight and the amount of exercise used in the studies only expended this amount of calories in a week. The psychological studies mentioned in the article are based purely on hypotheses and the “brown fat” theory is irrelevant and unproven.

One of the main theories that the article is based on, it that exercise increases ones appetite but as Dr Goedecke says, scientific studies have shown that exercise actually helps to regulate ones appetite. In other words one is better able to judge ones real hunger and satiety after exercise than if not exercising. In fact, there is a period after exercising where ones appetite is reduced. So those of us who eat more after exercise are doing so purely because we feel we deserve to eat more or because we can afford to eat more because we have exercised.

The article does state that exercise does have some positive effects on health and mentions mental health and back pain specifically. It also claims that it is more important to lose weight than exercise for those needing to improve their cardiovascular health. However other studies have shown that this is not true and that exercise (even without losing weight) can substantially improve cardiovascular health. The article does not mention the other vitally important benefits of exercise that include reducing cholesterol levels, improving insulin resistance (i.e. better blood sugar control in diabetics), increasing bone density and therefore helping to prevent osteoporosis.

As for weight loss, the reality is that intense exercise is not enough; diet control and energy restriction is also vital. Exercise does increase fat break down and utilization and therefore makes body fat control easier and scientific studies have shown conclusively that those who exercise will maintain their weight loss better. It is not always realistic (especially for those who are very overweight or obese or elderly) to exercise for 60 – 90min daily, but even just doing 30-45minute of intense exercise will make a difference. Also by increasing ones daily energy expenditure from just living (taking the stairs, walking  the dog, gardening) will make a difference.