Weight Loss Demonstrated In Controlled Clinical Trials

The following scientific article reviews the randomised controlled trials of various weight losing regimes: 'Obesity: weight loss without drugs: a balanced diet avoiding high-calorie foods, plus exercise. Prescrire Int. 2007;16:162-7.'

The authors performed 'meta-analyses', which are analyses summarizing the results of a large number of randomized controlled trials. The results were as follows:

A meta-analysis of 32 randomised controlled trials involving obese patients showed that moderate and well-balanced calorie restriction is more effective than any other diet, resulting in an average weight loss of about 5 kg after one year.

A meta-analysis of 35 randomised controlled trials involving obese patients showed that a combination of dieting and increased exercise is more effective than either measure alone. Increasing physical activity also helps to maintain weight loss.

A meta-analysis of 19 randomised controlled trials showed that the addition of active support, such as behavioural therapy, makes dietary weight loss measures more effective in obese patients. Behavioural therapy with spousal participation seems to be most effective, with half of trial participants losing about 7 kg after one year.

Interventions that do not involve assistance from healthcare professionals are hardly any more effective than dieting alone.

In practice, a variety of non drug measures can help obese patients to lose weight. However, they only lead to modest enduring weight loss and they have a limited impact on prevention of complications.

The clinical trials of treatments for obesity have not taken into account the social, environmental or psychological factors that contribute to obesity, nor the individual's history of obesity and previous treatments, nor the possible impact of dieting on quality of life. This limits the conclusions that can be drawn from these trials.