Here is a great interview with Linda Bacon, author of Health at Every Size: The Surprising Truth About Your Weight (HAES), about the dangers of intentional weight loss. Here is her peer-reviewed article that compiles information from numerous studies to support the claims that intentional weight loss is detrimental to health, as well as supporting the Health at Every Size approach It’s very long but very accessible and interesting, and I highly recommend reading it. Below are a few excerpts.
Concern has arisen that this weight focused paradigm is not only ineffective at producing thinner, healthier bodies, but also damaging, contributing to food and body preoccupation, repeated cycles of weight loss and regain, distraction from other personal health goals and wider health determinants, reduced self-esteem, eating disorders, other health decrement, and weight stigmatization and discrimination.
Only studies with an explicit focus on size acceptance were included. Evidence from these six RCTs indicates that a HAES approach is associated with statistically and clinically relevant improvements in physiological measures (e.g. blood pressure, blood lipids), health behaviors (e.g. physical activity, eating disorder pathology) and psychosocial outcomes (e.g, mood, self-esteem, body image). All studies indicate significant improvements in psychological and behavioral outcomes; improvements in self-esteem and eating behaviors were particularly noteworthy.
Attempts to lose weight typically result in weight cycling, and such attempts are more common among obese individuals. Weight cycling results in increased inflammation, which in turn is known to increase risk for many obesity-associated diseases. Other potential mechanisms by which weight cycling contributes to morbidity include hypertension, insulin resistance and dyslipidemia. Research also indicates that weight fluctuation is associated with poorer cardiovascular outcomes and increased mortality risk. Weight cycling can account for all of the excess mortality associated with obesity in both the Framingham Heart Study and the National Health and Nutrition Examination Survey (NHANES). It may be, therefore, that the association between weight and health risk can be better attributed to weight cycling than adiposity itself.
It is also notable that the prevalence of hypertension dropped by half between 1960 and 2000, a time when average weight sharply increased, declining much more steeply among those deemed overweight and obese than among thinner individuals. Incidence of cardiovascular disease also plummeted during this time period and many common diseases now emerge at older ages and are less severe. (The notable exception is diabetes, which showed a small, non-significant increase during this time period.) While the decreased morbidity can at least in part be attributed to improvements in medical care, the point remains that we are simply not seeing the catastrophic disease consequences predicted to result from the "obesity epidemic."
That weight loss will improve health over the long-term for obese people is, in fact, an untested hypothesis. One reason the hypothesis is untested is because no methods have proven to reduce weight long-term for a significant number of people.
Psychologist Deb Burgard examined the costs of overlooking the normal weight people who need treatment and over-treating the obese people who do not (personal communication, March 2010). She found that BMI profiling overlooks 16.3 million "normal weight" individuals who are not healthy and identifies 55.4 million overweight and obese people who are not ill as being in need of treatment.