Weight loss caused by improvements to the quality of the diet is successful because its addresses the cause of the weight gain, which is metabolic disorder caused by low quality food. However, evidence suggests that calorie restriction and exercise regimens that do not address the quality of the food eaten have high failure rates where the subjects are followed long-term. Studies show that weight loss is possible if calorie intake is reduced or if energy expenditure is increase, but generally these are short-term studies. Longer-term studies show that at follow up, subjects often regress and within a year or two have regained the weight lost. This is particularly true when advice, counselling or chaperoned exercise sessions cease and the subjects are left to fend for themselves. This suggests that the support given to the subjects is an important component of the weight loss.
For example, researchers1 provided calorie restrictive diets to 24 obese (body mass index 27.6kg/m2) individuals that caused a weigh loss of 10kg in each subject. Follow up measurements of body weight were then made at various periods up to 4 years after the initial weight loss in order to assess the long-term success of the subjects. Subjects were given no advice on weight maintenance following weight loss, but were left to their own devices in order to maintain their weight. This was a deliberate study design in order to mimic a real-life scenario and reduce possibly bias created by study support. To aid this process weights of individuals were self reported by the study participants. The results showed that at 1 year follow up, subjects had regained a mean of 42% of the weight lost and at 4 years this figure had risen to 87% of lost weight.
These results support other studies in that weight lost through energy deficit is nearly always regained by the study participants in the long-term. In this study, by 4 years 44% of the subjects had regained over 75% of the initial weigh lost, but 37% had regained 100% of the weight lost. The authors reported that those individuals who exercised during the follow up period gained significantly less weight than the subjects who did not. However, regular exercisers did not differ significantly from occasional exercisers in their regained weight. This suggests that exercise was not the cause of the benefit, which was perhaps caused by some other factor such as motivational bias. This is supported by data from the normal weight control group, that showed no difference in weight changes between those who exercised and those who did not.
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