Weight vs. diet: which is more important for your risk of diabetes?

A common criticism of the Mediterranean Diet is that it is not just a pattern of eating but is inextricably affected by the culture it is based in. That is, a Mediterranean Diet's effects also benefit from the Mediterranean and European culture.

It's true that people in European and Mediterranean countries tend to have a lower Body Mass Index than Americans, spend less time sitting, and place more of an emphasis on getting enough sleep as well as more quality leisure time.

Using data gathered for ARIC (Atherosclerosis Risk in Communities), a prospective cohort study, authors affiliated with Johns Hopkins, the National Institutes of Health (NIH), and the University of Minnesota sought to find out if a Mediterranean-style diet might be linked with a lower risk of diabetes here in the United States (Nutr & Diab 2020;10:8).

ARIC began recruiting participants from 1987 through 1989 from four US areas: Washington County, Maryland; suburban Minneapolis, Minnesota; Jackson, Mississippi; and Forsyth County, North Carolina.

At the start of the study all participants were between 45 and 65 years of age and worked with a trained interviewer to fill out a detailed food frequency questionnaire to assess their usual diet. Further, their blood pressures and height and weight were measured and they responded to detailed demographic survey that among other things asked about physical activity, smoking, health and family history, and education.

Follow-up visits took place in 1990-92, 1993-95, 1996-98, 2011-13, 2016-17, and 2018, and the dietary questionnaire was repeated at the third visit, in 1996-1998.

After excluding those participants with a history of heart disease, diabetes, or cancer, nearly 12,000 American men and women participated in the study.

Using the dietary questionnaires, the researchers were able to assign each participant a Mediterranean diet score (slightly modified for American food culture) on a scale of 0-9, with 9 being the highest level of adherence to a Mediterranean-style diet. At the close of data gathering, in 2018, the authors could compare the dietary scores of those who were diagnosed with diabetes over the course of the study with those who did not.

For the purposes of their analysis the authors grouped Mediterranean diet scores into 5 increasing levels: 0-2, 3-4, 5, 6, and 7-9. After taking into account clinical measures such as blood pressures and glucose scores as well as BMI, education, and smoking status, the authors found "no direct assocations" between Mediterranean diet scores and the risk of diabetes.

That said, when the authors focused on specific elements of the Mediterranean diet, they found that higher scores for red and processed meat (meaning the participant ate less red and processed meat than the average) was related to as much as a 16% lower risk of developing diabetes. Similarly, higher intake of nuts and legumes also seemed to contribute to a lower risk of diabetes.

Most interesting for me as a physician is when the authors looked at only the Black participants, they found that "associations between [Mediterranean diet] scores and ... diabetes were stronger among black compared to white participants" to the tune of a 5% decrease in risk for every 1-point increase in a participant's Mediterranean diet score. (Whites saw just a 3% reduction in risk.)

The associations were also stronger for those with a clinically normal Body Mass Index, where every 1-point increase in one's score meant a 6% reduction in risk of diabetes compared to a 3% reduction in risk for those who were overweight and 2% for those who were clinically obese.

What this means for you

This study suggests that one's weight is just as, if not more important than what one eats - at least in terms of diabetes risk. Yet diabetes is not the only chronic condition affected by diet - there's heart disease, cancer, and Alzheimer's, to name a few. If you are overweight, worry first about improving your Mediterranean diet score: shoot for improving it by at least two points. Worry about the pounds later.

First posted: August 19, 2020