[Contraindications to weight reduction].

It is relatively well accepted that weight gain, even within the range of normal weight, is detrimental for health. The claimed long-term benefit of intentional weight loss is mainly based on a few observational trials, confounding intentional and non-intentional weight loss. The few data on obesity-related diseases prevented by intentional weight reduction have not been replicated. Thus, for lack of level-one evidence it is to date doubtful whether voluntary weight loss should be intensively recommended to obese individuals rather than other lifestyle-interventions, e.g. exercise training. The aim of this overview is to discuss some of the contraindications to intentional weight loss often ignored in recent debates. There is no intention to question the increased risk of overweight on morbidity and the need for preventing weight gain in our population. Besides well-known consequences secondary to rapid weight loss, e.g. gallstones and electrolyte disorders, some new aspects or more debated issues are discussed. Recent compelling data indicate a significant bone density loss after weight loss of a few kilograms. Knowledge on the impact of weight cycling mainly relies on cross-sectional data. So far there is no concluding evidence of adverse pathophysiological effects from weight cycling. Repeated dieting has been associated with eating disorders, although the cause-effect relationship has not been well established. At least on an empirical basis there seems to be a tolerance effect after repeated weight losing efforts. Pharmacotherapy tends more and more to be part of weight loss interventions. Although the currently available drugs are designed for long-term treatment, in practice they are rarely used longer than a few months, and therefore their use can be entirely questioned. Nonetheless, if employed properly for weight loss and weight maintenance, i.e. "for life", additional data on long-term effects on health are needed. Such risks can then be weighed against the risk of remaining obese. Even a limited detrimental effect on blood pressure, such as known for sibutramine, could compromise the beneficial effect of the drug on weight loss and maintenance. Further, the financial burden of weight loss is not to be underestimated. Besides diets and weight loss programs being a multi billion dollar business, the cost of patient care in cases of surgery for gallstones has, among other economic implications, to be considered. Finally, with the example of the recently investigated impact of fitness level on health, exercise training may be an alternative to weight loss. Whether obese or not, cardiovascular fitness is a strong, independent predictor of cardiovascular mortality and overall mortality. Most obese being unfit, a greater preventive impact might come from becoming more fit than from losing weight. This should only illustrate that there is still a long way to go until we have sufficient scientific data to be able to tell whether in the management of obesity weight loss or other interventions are of higher priority. In part, current recommendations to lose weight are biased by societal pressure, which overrules simple scientific evidence.