Somewhat surprisingly, the link between body weight and death risk is stronger among adults without diabetes than among those with the disease, according to a new study.
The findings need to be taken into account in population studies examining the association between weight and death risk, said Chandra Jackson, of the Harvard School of Public Health, and colleagues.
The researchers analysed data from nearly 7 5000 black and white American adults, aged 35 and 75, who took part in the US National Health Interview Survey and were followed for six years. 5% of the participants had diabetes.
The people with diabetes had a higher death rate than those without diabetes. The researchers also found, however, that death rates for overweight people without diabetes were higher than for overweight people with diabetes, according to the study, which appears on 12 August in the Journal of General Internal Medicine.
Obesity increases the risk for serious health problems such as heart disease, type 2 diabetes and certain cancers, and obese people generally are considered to have a higher risk of death than those with normal weight.
These findings suggest that weight may have a different impact on death risk for diabetics than for people without the disease. Because of this, people's diabetes status should be taken into account in future weight/death risk studies, in the same way that heart disease, smoking and cancer are taken into account, the researchers said.
"This finding was surprising, but it may be due to a commonly observed phenomenon in chronic disease epidemiology called 'reverse causation', where a person's weight at the time of the survey can be affected by their disease if it leads to weight loss and muscle wasting during advanced stages," Jackson said in a journal news release.
"This apparent obesity paradox that has been observed in the past among individuals with diabetes may actually be due to methodological limitations that can bias these types of studies," she said.
"From clinical and public-health points of view, achieving and maintaining a healthy weight should continue to be recommended for both those with and without diabetes," Jackson said.
The U.S. National Institute of Diabetes and Digestive and Kidney diseases outlines the health risks of being overweight.