That forced calorie restriction diets cause short-term ‘weight’ loss in not contentious. Evidence from clinical trails shows that energy restriction causes weight loss for the first 6 to 12 months. However, that these diets are not effective at causing body fat loss without excessive decreases in lean mass is also well evidenced. In fact as much as 20 % of weight lost during energy restriction can be accounted for by skeletal muscle, which deleteriously affects resting metabolic rate (RMR). The failure rate of forced calorie restriction diets is also high, and in the long-term, participants often regress such that their body fat percentage increases beyond the original starting value. The focus of ‘weight’ loss rather that body compositional improvements by the mainstream medical establishment is not therefore helpful, and the obstinate way in which proponents of such forced calorie restriction diets ascribe blame to the dieter, rather than the diet, is reflected by a lack of progress in this field.
A study published in the American Journal of Clinical Nutrition1 investigated the effects of a forced calorie restrictive regimen on weight loss in overweight women. The women were observed after enrolment in a commercial weight loss programme in Sweden, to which they paid their own fees. Subjects were fed either a liquid very low calorie diet (VLCD) of 500 kcal per day, a semi-liquid semi-solid low calorie diet (LCD) of 1200 to 1500 kcal per day or a solid food restrictive diet of 1500 to 1800 kcal per day, for an initial 3 month period. After this time, the subjects were asked to maintain the weight loss thorough increased exercise, group support and nutritional advice. The liquid food was a pre-prepared formula containing 13 grams of protein, 15 grams of carbohydrate, 2 grams of fat and 3 grams of fibre per 125 kcal. Solid food recommendations were to eat a higher protein, low glycaemic index diet.
Following one year, the subjects on the VLCD had lost 11.4 kg, the subjects on the LCD had lost 6.8 kg and the subjects on the restrictive solid food diet had lost 5.1 kg. This supports other finding to show that calorie restriction diets work in the short-term. However, the ‘weight’ loss recorded in the study did not include a measure of lean mass or fat mass. The waist circumference of the subjects did improve for each group, indicative of a reduction in abdominal adipose tissue. Therefore while the VLCD subjects did lose more weight, it is unclear if they lost more body fat. Results from previous studies would tend to suggest that the VLCD and LCD groups would have lost more lean mass in a addition to their fat when compared to the subjects consuming a higher energy solid food diet. In addition, because the study did not consider the fact that energy restriction would also have included fructose restriction, it is not possible to conclude that the weight loss was due to the energy intake.
The failure rates on the diets were high with 18 % of subjects failing to adhere to the VLCD, 23 % of subject failing to adhere to the LCD and 26 % of subjects failing to adhere to the solid food diet. Evidence from other studies shows that drop out rates increase significantly as the diet progresses such that most individuals have regained 95 % of lost ‘weight’ by 5 years. This regained weight is often made up almost exclusively of fat, resulting in a net loss of skeletal muscle during a weight loss weight regain cycle. The deleterious effects of a lowered RMR is reflected in decreased circulating level of triiodothyronine (T3), which can substantially increase the likelihood of further gains in body fat. Because forced calorie restriction does not address the poor quality of the nutritional intake, when normal eating is reintroduced the underlying causes of the obesity further increase the risk of weight regain.
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