In the popular imagination, diabetes and obesity are closely linked — with some people assuming, wrongly, that you need to be overweight or obese to develop type 2 diabetes. In reality, of course, excess body weight is just one risk factor for type 2 diabetes, along with your family history, diet, physical activity level and more.
But it’s also true that while obesity isn’t the only risk factor for type 2 diabetes, it is one that should be taken seriously. Treating obesity isn’t always easy, but research shows that in people with excess body weight, losing just 5% to 10% of your weight can significantly improve your blood glucose control if you already have diabetes, and possibly reduce your risk or developing diabetes if you don’t have it.
A new study shows just how strong of a factor obesity is in the development of type 2 diabetes, finding that up to half of cases are linked to it.
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Obesity contribution varies by sex and race
The study, published in the Journal of the American Heart Association, found that obesity is a major contributor to the risk of developing type 2 diabetes — but that this contribution isn’t equal across the population. Instead, it varies according to your sex and your race.
Using data from a larger study called MESA (Multi‐Ethnic Study of Atherosclerosis), researchers looked at the risk of developing diabetes during a study period that lasted from 2000 to 2017. Participants included in the analysis belonged to one of three different racial or ethnic categories — non-Hispanic white (54% of participants), non-Hispanic Black (33%), and Mexican American (13%) — and didn’t have diabetes at the beginning of the study. The average age of participants at the beginning of the study was 61.
Looking at whether participants were obese, and then whether they developed type 2 diabetes, the researchers came up with a “raw” risk calculation, as well as one that adjusted for factors including age, study site location, physical activity, diet, income and education level. Over a median follow-up period of about nine years, 12% of participants developed diabetes. The overall risk of developing diabetes was 2.7 times as high for obese participants as for those who weren’t obese.
But the contribution of obesity to diabetes was larger or smaller in different subsets of participants. As noted in an article on the study at MedPage Today, among white women, 53% of diabetes cases were linked to obesity. This number was 42% for Mexican American women and 39% for Black women. Obesity played a smaller role in diabetes risk for men, with just 30% of diabetes cases linked to obesity in Black men — the smallest proportion of any group.
Another notable finding was that in some groups, the relationship between obesity and diabetes wasn’t constant throughout the study period. Mexican American women, for example, saw a jump in how many diabetes cases were tied to obesity, from 22% in the period of 2001–2004 to 38% in the period of 2013–2016.
Obesity and diabetes: a complicated relationship
While this study highlights the role of obesity in developing type 2 diabetes, it also shows that the relationship between the two isn’t straightforward — with factors like sex and race affecting how strongly they’re connected.
One somewhat surprising finding is that while Black women have a higher risk for diabetes than white women, obesity accounts for a lower proportion of diabetes cases in Black compared with white women. This suggests that other factors — possibly stress, pollution, or anything else that could be linked to race — account for the difference in diabetes risk between these groups.
This study supports the idea that policies or interventions aimed at reducing obesity could put a big dent in the rate of new diabetes cases. But it also demonstrates that other factors play a role in diabetes risk, and shows that more studies are needed to learn about which factors are more or less important in different groups.