(NaturalNews) A recent study published in the New England Journal of Medicine has debunked the findings of some recent studies which suggested that diabetics who were overweight or obese could have lower mortality rates than their normal-weight counterparts.
The study, led by researchers from the Harvard School of Public Health, looked at 2,457 men who took part in the Health Professionals Follow-up Study (HPFS) and 8,970 women who took part in the Brigham and Women's Hospital-based Nurses' Health Study (NHS); the subjects were followed for 26 years and 36 years respectively.
The study found that there was a positive link between body mass index (BMI) measured at the point of diabetes diagnosis and the risk of death from all causes. Those who had normal weight had the lowest risk of death, while overweight or obese study subjects did not enjoy lower mortality rates.
"Obesity-mortality paradox" debunked
Obesity is a known risk factor for ailments such as diabetes, heart disease and cancer, and studies have revealed that obese people with these conditions have higher mortality rates. However, some recent studies have also suggested the opposite - that obesity has a beneficial effect and actually protects against death from all causes and death due to conditions such as heart failure, stroke and diabetes. This "obesity-mortality paradox" has raised a fair amount of controversy.
Those studies, though, have some limitations, according to the authors of the recent Harvard study. These include small sample sizes, measuring BMI years after diabetes was diagnosed, and, significantly, not accounting for weight loss from smoking and undiagnosed chronic diseases.
Smokers and chronically ill persons could be residing in the same "normal weight" study group as those who were lean and healthy. Because these persons have inherent risk factors, they would skew the relationship between weight and mortality, making the "normal weight" group seem worse off than they should be and the "overweight" group seem better off than they should be.
"After carefully controlling for many of these factors in our analysis, we observed that excess weight in those with diabetes was not advantageous for survival. These findings underscore the importance of addressing methodological biases in the analysis of BMI and mortality," said Deirdre Tobias, a research fellow in the Department of Nutrition at the Harvard School of Public Heath who led the study.
Limitations of BMI
There is another issue - BMI is not a precise enough indicator of body fat content. As pointed out by researchers from the Perelman School of Medicine, BMI does not account for factors like fat distribution, muscle to fat ratio, as well as the gender and ethnic differences when it comes to body composition - and these are major factors when it comes to health and mortality.
Some persons may have BMIs which suggest they are obese, but research has shown some of them may actually have improved metabolic profile and lower cardiovascular risk, while some persons with normal-range BMIs may actually be metabolically unhealthy
Going forward, it is clear that better measures of obesity and being overweight that can better predict disease and mortality risks need to be formulated. In the meantime, Frank Hu, professor of nutrition and epidemiology at the Harvard School of Public Health and a senior author of the recent study, summed up his team's findings: "These data dispel the notion that being overweight or obese confers survival advantage among diabetic patients. Clearly, weight management is an important therapeutic strategy for overweight or obese individuals with type 2 diabetes."