Two studies, reported in the American Journal of Epidemiology in 2002, found that losing 20 or more pounds did not reduce the risk of heart disease in obese individuals.
One study, done by a team led by Dr. David F. Williamson of the National Center for Chronic Disease Prevention and Health Promotion at the Centers for Disease Control and Prevention in Atlanta, Georgia, was based on analysis of the 12-year death rates and fluctuations in weight in over 49,000 overweight white men between the ages of 40 and 64. The team specifically focused on deaths linked to cardiovascular disease, diabetes, and cancer.
Among healthy men and men with reported health conditions, intentional weight loss did not make a difference in either total mortality or mortality from cardiovascular disease. Reuters reported that the team found these results 'confusing' in light of the current trend of thought about obesity and heart disease. (The Cooper Institute studies of 20,000 men over a period of 20 years found that the key element in maintaining health was exercise, regardless of how fat a person was or how much they weighed. see Colles, Lisa: FAT, London - 1998)
The second study from researchers at the University of Minnesota in Minneapolis, focused on similar data in a group of over 40,000 women enrolled in the Iowa Women's Health Study. The women, aged 55 to 69, provided data on intentional and unintentional weight loss since age 18. The researchers found that, once again, intentional weight loss (i.e. DIETING!) had no significant effect on risks for death from heart disease or other causes, "nor did it provide any protective effects."
The researchers observed though that 'unintentional' WEIGHT LOSS _did_ raise the risk of cardio vascular disease. Other studies, reported by Dr Glenn Gaesser, found that ANY weight loss of 10 percent or more bodyweight, raised the risk of morbidity. Among the studies finding this, were the Metlife studies, which eventually did NOT result in weight charts according to the studies since no clear link between obesity and death could be found.
The two studies did report a rather significant reduction in deaths from diabetes in those who lost weight. Cleaning up the diet and exercising (which people on diets tend to do) does have a beneficial effect on diabetes but of course, one does not have to 'lose weight' to experience this.
A search of the web in July 2011, still found no direct link between losing
weight and lowering risk of heart disease.