The best way to prevent weight regain after you've worked so hard to lose it...

A new study has shown why it's so difficult to prevent weight regain following several months of dieting.

A research team, based at Maastricht University, showed that just ten weeks on a very low-calorie diet actually reduces the number of fat calories your body burns each day. This post-diet drop in fat oxidation could explain why many people find it such a challenge to prevent weight regain.

A group of 40 overweight men took part in the study. They were divided into two groups.

• Diet only.

• Diet plus aerobic exercise.

During the first six weeks of the study, subjects in both groups were given a very low-calorie diet providing just 500 calories daily. From weeks 7 to 10, they gradually increased their food intake.

The men in the exercise group completed three sessions per week, consisting of walking and underwater exercise. Each workout lasted for around one hour. The table below shows you what happened in both groups following 10-12 weeks of diet and exercise.

TABLE 1. Changes in body composition following 10-12 weeks of diet and exercise.

As you can see, both groups lost roughly the same amount of fat and muscle. However, tests showed that the subjects who didn't exercise had a reduced capacity to burn fat, both at rest and during exercise.

This post-diet decline in the number of fat calories used as energy offers one explanation as to why it's so easy to put weight back on after you've lost it. The good news is that exercise serves to completely "block" this decline, which could help you prevent weight regain.

There are two important points you can take from this study.

• Low-intensity aerobic exercise (such as walking) performed three times per week has little effect on the rate at which you lose fat. A combination of weight training and interval exercise is a far more effective way to train if you want to lose fat faster.

• The benefits of low-intensity aerobic exercise are more apparent when you're trying to keep the weight off. The exercise doesn't have to be particularly vigorous or demanding. Just three hours of walking each week appears adequate to prevent the post-diet decline in fat oxidation.

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Reference
van Aggel-Leijssen, D.P.C., Saris, W.H.M., Hul, G.B., & van Baak, M.A. (2001). Short-term effects of weight loss with or without low-intensity exercise training on fat metabolism in obese men. American Journal of Clinical Nutrition, 73, 523-531