Compelling new evidence indicates that adopting a Mediterranean diet, reducing calories, and increasing physical activity can significantly lower the risk of Type 2 diabetes.
A comprehensive randomized trial in Spain revealed that older adults at risk for diabetes who adhered to this diet, cut calories, and exercised regularly were 31% less likely to develop the disease over six years compared to those who only followed the Mediterranean diet. This diet prioritizes fresh produce, whole grains, nuts, legumes, olive oil, and fish.
The findings expand on earlier research that showed participants who only followed the Mediterranean diet were 30% less likely to develop diabetes compared to those on a low-fat diet. In that study, participants did not limit calories or increase physical activity.
Published in The Annals of Internal Medicine, the study adds to extensive research showing that diet, physical activity, and weight loss are crucial in reducing the risk of diabetes and other chronic illnesses.
“It confirms much of what we know,” stated Elizabeth Selvin, an epidemiology professor at Johns Hopkins Bloomberg School of Public Health.
Diet and physical activity “are key risk factors for cardiovascular disease and diabetes,” Selvin noted, though they are challenging to study. These large randomized trials of dietary and behavioral interventions over several years are tough but vital, she added, as they provide the strongest evidence that specific interventions, rather than other factors, cause the observed outcome differences.
The role of diet, exercise, and weight loss in reducing diabetes risk was established in the landmark Diabetes Prevention Program trial in 2002. Participants assigned to education, 150 minutes of exercise weekly, and a low-calorie, low-fat diet to reduce their weight by 7% showed a 58% reduction in diabetes risk compared to a placebo group.
Dr. Selvin’s research, published in Nature Medicine, found that a modified DASH diet rich in fruits, vegetables, and low-fat dairy helped patients with diabetes lower their average blood glucose levels. They also spent more time within the recommended range. Another study in Nature Medicine linked the Mediterranean diet to reduced Alzheimer’s risk among those with high genetic risk.
The Spanish trial tracked nearly 5,000 adults aged 55 to 75 who were overweight or had metabolic syndrome but no cardiovascular disease or diabetes history. Metabolic syndrome includes conditions like high abdominal fat, blood sugar, and blood pressure, increasing diabetes and chronic disease risks.
Intervention group members met with a dietitian for six years, learning to follow the Mediterranean diet and cut calories. They were advised to exercise 45 minutes daily, six days a week, with brisk walking or equivalent aerobic activity, plus strength and balance training two to three times weekly. Control group participants received only Mediterranean diet education and met less frequently with dietitians. All participants received olive oil, a costly diet component.
On average, the intervention group lost over seven pounds and reduced waist circumference by 1.4 inches over six years, compared to just over one pound and 0.1 inch in the control group. The intervention group’s weight loss represented 3.7% of body weight, less than what doctors often consider necessary to reduce diabetes incidence.
“The good news is that even a modest change impacted the risk,” said Miguel Ángel Martínez-González, a public health professor at the University of Navarra and one of the trial’s investigators.
The 31% relative reduction in diabetes risk meant the intervention measures would lead to about three fewer diabetes cases per 100 people.
“We can’t pinpoint the key factor here,” said Dr. Tirissa J. Reid, a Columbia University Irving Medical Center associate professor not involved in the trial. However, weight loss’s impact on reducing diabetes risk was likely significant, she added.
Before Type 2 diabetes or prediabetes appears, patients often develop insulin resistance, where the body poorly responds to insulin. Physical activity and high-fiber diets like the Mediterranean diet, along with weight loss, can reduce such resistance.
The diet, exercise, and weight loss might also reduce inflammation and oxidative stress, which damages cells, researchers noted. Combined, these benefits may lower diabetes risk.
“It’s like an orchestra,” said Dr. Jordi Salas Salvadó, a nutrition professor at Universitat Rovira i Virgili in Spain and the study’s senior author. “One instrument sounds good, but when several play together, the song is better.”
A notable trial aspect, mentioned by Nicole Patience, a registered dietitian at Joslin Diabetes Center in Boston not involved, was the education and support intensity.
Six years is “a long time to help people stick to their goals” and make lasting behavior changes, she said. Participants in the treatment group had regular, frequent dietitian contact, unlike the control group. The support’s impact versus the dietary and activity intervention itself is unclear.
Replicating such contact levels in real life is challenging, and the Mediterranean diet might not suit everyone.
Nonetheless, Patience said this study shows that small dietary changes and added exercise can greatly improve long-term health.
(The writer is a New York Times health reporter)
The article originally appeared in The New York Times
