Being overweight or obese has long been identified as a risk factor for Type 2 diabetes. In fact, the risk of developing Type 2 diabetes appears to steadily increase along with body weight, so that the diabetes risk of an obese person is as much as 80 times higher than the risk of someone with a low-normal body-mass index. There has long been some dispute, however, about whether being overweight or obese automatically carries a higher diabetes risk, or whether secondary factors such as blood pressure, family history of diabetes, sedentary behavior, or blood triglyceride levels are actually responsible for the increase in risk.
A recent study sought to separate out these factors and discover whether obesity alone results in a higher diabetes risk, or whether you can be “overweight but healthy,” at least when it comes to avoiding diabetes. Published last month by the journal Diabetes Care, the study looked at almost 34,000 men ages 25 and above who were members of the Israel Defense Forces. (Since military service is mostly mandatory in Israel, participants in this study more closely represented the general male population than would be the case in many other countries’ armed forces.) According to a Medscape Medical News article on the study, at the beginning of the study period, 49% of the men were normal-weight, 38% were overweight, and 13% were obese. Participants were followed for an average of six years, during which 2.2% of them were diagnosed with Type 2 diabetes. Every additional unit of body-mass index at the beginning of the study was associated with a 10.6% increase in the risk of developing diabetes during the follow-up period.
In addition to their weight status at the beginning of the study, participants were classified according to a number of other risk factors for Type 2 diabetes, including elevated triglycerides or use of lipid-lowering drugs, an elevated fasting glucose level, elevated blood pressure or use of blood-pressure-lowering drugs, and low HDL (high-density lipoprotein, or “good”) cholesterol levels. Not surprisingly, these risk factors were seen more often in overweight and obese participants, with only 15% of obese and 32% of overweight participants totally free of them, versus 55% of normal-weight participants. But even when looking only at participants who were free of these additional risk factors, extra weight was still found to be damaging when it came to diabetes. Within this group, overweight participants were 1.89 times more likely, and obese participants were 3.88 times more likely, than normal-weight participants to develop diabetes.
Furthermore, having additional risk factors (elevated triglycerides, etc.) made overweight and obese participants far more likely than normal-weight participants to develop diabetes. Among participants with three or more of these risk factors, those who were obese were 6.05 times as likely to develop diabetes as those of normal weight.
One factor not considered in this study was the type and location of body fat among overweight and obese participants. As Diane Fennell noted in a 2012 blog entry, a study that year found that excess visceral fat — fat surrounding the internal organs — and insulin resistance were responsible for the increase in diabetes risk associated with obesity, and explained why some obese people get diabetes and others don’t. It may thus still be possible — if extremely rare — to be overweight or obese and still not have an elevated risk of developing diabetes.
What’s your take on weight and diabetes — do you think there’s an attitude among many people that “getting fat” leads to diabetes? Do studies like this one reinforce that view, even if they offer a more nuanced perspective? Is it useful to study the relationship between weight and diabetes, without also examining how factors such as genetics, dietary choices, and physical activity level lead to overweight and obesity in the first place? Leave a comment below!