31 August 2006

Humans: Designed For Fatness

by Kate Melville

Scientists at an obesity conference in Australia have heard how the human body is designed from the ground up to strongly resist attempts to lose weight. Queensland University appetite regulation and energy balance researcher, Dr Neil King, explained to the conference attendees that our bodies have strong mechanisms to defend against attempts to lose weight, but very weak mechanisms to prevent weight gain.

Dr King conducted two studies on weight loss which demonstrated the "plateau effect"; where weight loss from exercise and calorie restrictions stops at a certain point. "The effect has been known about for some time and weight management consultants recommend longer exercise times, higher intensity or cross training to combat it," Dr King said. "But these studies show that a plateau in body weight occurs even in the face of a continued negative energy balance."

Dr King's first study involved 30 obese men and women taking part in a 12-week, laboratory-based exercise program in which they exercised five times a week. The second study looked at weight loss in 200 males on a commercial weight loss program comprising exercise and dietary advice.

In the first study, the subjects' energy deficit was caused by exercise only, which was fixed and imposed; in contrast to the second study, where subjects used diet and exercise to lose weight but chose how much they did of each. Dr King said the first group's weight loss during the first eight weeks averaged 3kg but it "plateaued" at week eight and weight loss for the next four weeks was markedly reduced (.7kg).

The second group had a variable pattern of weight loss, but it also showed a plateau. "There appears to be little at this stage to predict the onset, duration and frequency of the plateau," Dr King said. He added that our energy balance system was programmed to cope with famine, "not the current obesogenic environment which enforces inactivity and a plentiful food supply."

Source: Research Australia