February 17, 2021 | Erin Bluvas, bluvase@sc.edu
Research led by health promotion, education, and behavior associate professor Brie Turner-McGrievy has revealed that popular diets are not necessarily the most healthy. Turner-McGrievy and her team compared 40 diets rated by 25 physicians and nutritionists for U.S. News & World Report in 2018 – finding significant differences in nutritional quality among the diet types. They published their work in Clinical Nutrition ESPEN.
“Almost half of all adults in the United States have tried to lose weight in the past year,” says Turner-McGrievy, who is the deputy director for the South Carolina SmartState Technology Center to Promote Healthy Lifestyles and principal investigator of the NEW Soul Study. “While the general diet recommendation for adult weight loss is to reduce calorie intake, there are a variety of dietary strategies that can be used to achieve that goal.”
As demonstrated by the number of diets included in the U.S. News & World Report’s annual review, there are many dietary approaches/patterns available. The report includes overviews of each diet, expert ratings, and study results related to whether the diet is effective for weight loss, easy to follow, and costly. It also includes a sample meal plan and a summary of research related to the diet in connection with chronic conditions (e.g., diabetes, heart disease).
With this study, the researchers categorized the 40 diets identified by U.S. News & World Report into four types: moderate (i.e., reducing energy intake from all food groups, particularly those high in fat and added sugars), plant-based (i.e., excluding food groups, such as animal products), low-carbohydrate (i.e., limiting carbohydrate-containing foods), meal replacement (i.e., replacing foods with pre-made, calorie-controlled portions). Using the Healthy Eating Index to assess overall alignment with U.S. Dietary Guidelines and the Dietary Inflammatory Index (DII®) to measure inflammatory potential, they analyzed these approaches for differences and commonalities in food groups consumed, nutritional composition, and diet quality.
The authors found significant differences among the four types in a number of areas (e.g., energy, sugars, fiber, fats, carbohydrates, cholesterol). Specifically, the moderate and plant-based diets had higher Health Eating Index scores (i.e., better alignment with fruit/vegetable, whole grains, meat, etc. intake recommendations) compared to low-carbohydrate diets. Plant-based and moderate diets (particularly the Macrobiotic, Big Loser, and Ornish) had stronger anti-inflammatory DII scores.
“These findings provide useful information on nutrient adequacy of popular diets and can help inform the design of future healthy meal plans by assessing where there is consensus and agreement among diets,” Turner-McGrievy says. “They can also highlight possible nutrient and food group gaps that could be potentially harmful to health.”
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