What 16 Systematic Reviews Say about Diet Patterns and Obesity Risk

Dr Khushboo Agarwal, Associate Professor, Endocrinology, GSVM Medical College, Kanpur

An umbrella review pulling together 16 systematic reviews and 143 individual studies found that the Mediterranean diet is consistently linked to lower obesity risk, offering some of the strongest evidence yet for shaping national obesity prevention strategies.

Dietary pattern research has grown substantially over the past two decades, but findings across individual studies and reviews haven't always pointed in the same direction. To make sense of this body of evidence, researchers conducted an umbrella review — a review of reviews — aimed at summarizing what existing systematic reviews say about the relationship between different dietary patterns and overweight or obesity outcomes in adults.

Following PRISMA guidelines, the researchers searched CINAHL, MEDLINE, Cochrane, Scopus, EMBASE, and Web of Science for systematic reviews on dietary patterns and weight gain or overweight/obesity outcomes. This search identified 16 systematic reviews encompassing 143 unique studies published between 2001 and 2019, with overall quality scores ranging from 4 to 10.

The results varied by dietary pattern. Six reviews, drawing on 2 of 11 cohort studies and 6 of 19 cross-sectional studies, reported statistically significant decreased odds of obesity associated with the Mediterranean diet, with odds ratios ranging from 0.53 to 0.73 in cohort studies and 0.35 to 0.88 in cross-sectional studies. Five reviews, based on 5 of 15 cohort studies and 10 of 45 cross-sectional studies, found an inverse association between weight gain or BMI and overall diet quality, with beta values ranging from –1.3 to –0.09. Two reviews reported that fruit and vegetable intake was linked to a decreased risk of obesity (odds ratio of 0.76) and weight gain (odds ratio of 0.26), based on 1 of 3 cohort studies and 1 of 2 cross-sectional studies, respectively. On the other end, five reviews examining mixed dietary patterns found that 3 of 40 cross-sectional studies reported an increased prevalence of obesity (odds ratio of 1.19) or abdominal obesity (odds ratios ranging from 1.07 to 1.27) associated with the Korean diet pattern.

The study concludes that Mediterranean diet patterns reduce the risk of obesity in adults. While they note that population-specific evidence on effective interventions is still needed, they argue that the defining characteristics of Mediterranean-type diets are important considerations for shaping national obesity prevention strategies.

(Reference: Seifu, C. N., Fahey, P. P., Hailemariam, T. G., Frost, S. A., & Atlantis, E. (2021). Dietary patterns associated with obesity outcomes in adults: an umbrella review of systematic reviews. Public health nutrition, 24(18), 6390–6414. https://doi.org/10.1017/S136898002100082 )