The more diverse your diet, or the greater the variety in foods you eat, the better you are — right? Well, maybe not. According to a news release, researchers at the Friedman School of Nutrition Science and Policy at Tufts University and The University of Texas Health Science Center at Houston (UTHealth), believe that diet diversity may actually be linked to lower diet quality and worse metabolic health. The study, entitled “Everything in Moderation – Dietary Diversity and Quality, Central Obesity and Risk of Diabetes,” was recently published in the journal PLOS One.
The researchers point out that the “eat everything in moderation” approach is an established dietary recommendation but one without actual empiric support. “We wanted to characterize new metrics of diet diversity and evaluate their association with metabolic health” said Marcia C. de Oliveira Otto, PhD, assistant professor at UTHealth School of Public Health and study’s lead author, in a news release.
The study used data from the Multi-Ethnic Study of Atherosclerosis, a trial with 6,814 participants of multiple ethnicities in the U.S. that measured diet diversity using different methods: total count (number of different foods eaten in a week), dissimilarity (the variations in food attributes necessary to metabolic health, like sodium, fiber, or trans-fat), and evenness (caloric distribution across different foods eaten). To evaluate how diet diversity was linked to changes in waist circumference, a crucial indicator of metabolic health, the diets were compared five years after the start of the study. The link between diet diversity and type 2 diabetes onset 10 years later was also assessed.
Neither an increase in waist circumference nor incidence of diabetes was seen when evaluating both evenness and food count, which means a greater dietary diversity was not associated with better outcomes. Those who actually had the greatest difference in food choices were the ones who had more weight gain, with a 120% increase in waist circumference when compared to participants with lower food dissimilarity. To compare these results, researchers also took into consideration the quality of the dietary intake in relation to metabolic health. Diet quality was evaluated using scores such as the Alternative Healthy Eating Index (AHEI) and the Dietary Approaches to Stop Hypertension (DASH). At five years, no relation was found, but at 10 years, a higher diet quality showed a 25% lower risk of developing type 2 diabetes.
“An unexpected finding was that participants with greater diversity in their diets, as measured by dissimilarity, actually had worse diet quality. They were eating less healthy foods, such as fruits and vegetables, and more unhealthy foods, such as processed meats, desserts and soda,” said Dr. Otto. “This may help explain the relationship between greater food dissimilarity and increased waist circumference.”
The study found that dietary diversity, assessed by food count and evenness, was also linked with higher intake of both unhealthy and healthy foods.
“Americans with the healthiest diets actually eat a relatively small range of healthy foods,” said Dariush Mozaffarian, MD, Dr.P.H., dean of the Friedman School of Nutrition Science and Policy at Tufts University in Boston and study’s senior author. “These results suggest that in modern diets, eating ‘everything in moderation’ is actually worse than eating a smaller number of healthy foods.”