Weight regain, or the `yo-yo' effect of weight loss is not restricted to humans. Scientists studying caribou in Northern Canada have shown that after a long drought during which these animals lose significant body fat, there is a rebound effect where fat gain in the good times leads to a greater body fat level than before the drought. Carolyn Pond, in her book `The Fats of Life', shows that this is also the case with other wild living animals.

In some early classic studies with humans carried out in the 1940s, Professor Jean Mayer of Harvard University found this when he examined the effects of starvation in conscientious objectors during the war years. Starvation caused big decreases in weight, and most notably, an increase in fatigue, irritability and depression. When eating resumed, the men studied gained more body fat than they had before starving and then found this harder to lose than before.

According to Professor Tim Wadden of the University of Pennsylvania, there are four potential causes of weight regain after significant weight loss. These are:

1. Compensatory changes in metabolic rate;

2. Non-adherence to a diet and exercise regime;

3. Living in a `toxic' or `obesogenic' environment (with high fat take-aways and sophisticated technology; and

4. The adverse behavioural effects of dieting (in particular hunger, binge eating, rigid perfectionist thinking and depression).

Depression and regain
Because depression was a symptom of Mayer's original starvation group, it was thought that this may be the factor that helps mediate weight regain. Wadden's Pennsylvania group studied this in groups of obese women put on three different dietary regimes 1. a portion controlled 1000 Cal/day diet 2. a conventional 1200Cal/day diet or 3. a modern non-dieting approach to improving body image.

While women in both groups 1 and 2 lost around 15kg over a one year period, there was no weight loss in the third group. More tellingly, there was no increase in depression in any group, hence suggesting that depression is not a necessary function of weight loss. So this discounts treatment of depression as a technique for dealing with weight regain.

Mechanisms of regain
The rebound effect of greater weight gain after a big loss appears to be the body's defence against possible future periods of starvation. It probably occurs as a result of physiological changes in appetite mechanisms and metabolism, but what signals the brain to stimulate these mechanisms is not clear.

According to Dr Wadden, techniques aimed at overcoming regain and improving maintenance which have been identified from the literature include:

1. Maintaining physical activity levels through exercise at a rate of 1500-2500 Cals per week (i.e. the equivalent of walking roughly 3-4km per day)

2. Losing weight slowly. Slow weight loss, in contrast to sudden losses do not seem to cause the same `bounce back' phenomenon.

3. Continuing to eat a low fat/low total energy diet.

4. Monitoring food intake, such as through a daily food diary, and

5. Learning techniques of dealing with periods of stress, particularly where this is a stimulant to over-eating.

Work carried out with the long running Swedish Obesity Study (SOS) has shown that long term (i.e. >12 year) maintenance of body weight is possible. For very big people, the best initial method for this is surgery. However, behavioural monitoring is likely to have as good an effect as use of any weight reducing drugs over the long term.

Summary

In many cases of weight loss, according to Wadden, it may be as important to maintain weight at a higher than desirable level, than it is to try to reduce it against all the odds.

For Reference:
Waden T. The management of obesity in 1998: From past failure to future attainment. 8th International Congress on Obesity, Paris, 1998 (IJO, 22(3): S69).

This Q&A modified from the Waist Watch newsletter.