Struggling with weight? Eat more legumes, cut red meat, and skip soda

Want to overcome obesity? A global review uncovers the strongest evidence on what to eat—and what to avoid—to manage weight and improve health.

Umbrella Review of Systematic Reviews and Meta-Analyses on the Consumption of Different Food Groups and the Risk of Overweight and Obesity. Image Credit: Igor Dutina / Shutterstock

In a recent study published in the journal Nutrients, researchers in Italy and Norway summarized evidence linking specific food groups with overweight and obesity risks.

Background

Did you know over 2.8 million deaths globally each year are linked to obesity? As obesity rates surge, it is crucial to understand how our daily food choices influence weight management and overall health.

Food groups such as whole grains, fruits, vegetables, nuts, legumes, meat, and sugary beverages all play critical roles in energy balance, either supporting weight control or contributing to weight gain. However, clear dietary recommendations can be confusing due to conflicting research outcomes.

Understanding the true impact of various food groups on obesity could guide healthier lifestyles and more effective public health policies. Hence, further comprehensive research is needed to provide clearer guidance.

About the study

Researchers conducted an umbrella review, systematically summarizing findings from previous systematic reviews and meta-analyses. Four major databases, Medline, Embase, Web of Science, and Epistemonikos, were thoroughly searched for relevant studies published until June 2024.

The criteria for selection included systematic reviews and meta-analyses of longitudinal studies, such as cohort studies and randomized controlled trials, examining the relationship between consumption of specific food groups and the incidence of overweight and obesity among adults aged 18 or older.

Studies were excluded if they involved children, animals, cross-sectional designs, non-systematic reviews, or were limited to a single country’s data without broader applicability. Thirteen eligible studies were selected from an initial pool of 2,925 articles, covering, on average, 166,100 participants and 36,760 cases per food group, although these numbers varied depending on the food group.

Each included study was independently assessed by multiple researchers for methodological quality using the standardized tool, “A Measurement Tool to Assess Systematic Reviews” (AMSTAR-2). Data extraction involved recording the number of studies, participants, cases, outcomes, exposure details, heterogeneity, and key findings, distinguishing clearly between high versus low consumption comparisons and dose-response relationships.

The findings were then synthesized into visual summaries, including forest plots and dose-response curves, highlighting the significance and direction of associations. Any discrepancies in assessments or data extraction were resolved through team consensus to ensure the reliability and accuracy of the reported findings.

Study results

The review synthesized data from systematic reviews involving, on average, 166,100 participants per food group. High consumption of whole grains, fruits, nuts, and legumes consistently showed protective effects against obesity and overweight, likely due to their high fiber content enhancing feelings of fullness and reducing caloric intake.

Specifically, high intake of whole grains resulted in significantly reduced obesity risk, with clear dose-response relationships showing continuous risk reduction with increased consumption. Similarly, nuts demonstrated beneficial effects at moderate consumption levels (~10 grams/day), although this protective effect appeared to level off at higher intakes.

Conversely, high consumption of red meat and sugar-sweetened beverages significantly increased obesity risk, reinforcing the public health message to limit these foods. Red meat’s association with obesity could stem from its high calorie and saturated fat content, potentially promoting fat storage and weight gain. Sugar-sweetened beverages were consistently linked to higher obesity rates, with low heterogeneity across studies, strengthening the robustness of this association.

Interestingly, vegetables may show a nuanced U-shaped dose-response relationship, although this trend was not statistically significant. Moderate vegetable intake (~250-400 grams/day) appears beneficial, but very high intakes do not clearly add more benefit.

Dairy products showed no significant association with obesity risk, and findings across different types of dairy were conflicting, highlighting a need for further research.

Refined grains showed a non-significant trend toward increased obesity risk, especially at higher consumption levels. This is likely due to their rapid digestion and high glycemic index, which cause spikes in blood sugar and insulin levels, potentially promoting fat storage.

Although processed meats showed a trend toward increased obesity risk, the findings were statistically non-significant, based on low-quality evidence, and highly variable across studies.

No available studies provided evidence on the association of obesity risk with fish, eggs, white meat, and added sugars, highlighting significant gaps in dietary research.

Overall, the research showed substantial heterogeneity across studies, particularly for nuts and processed meats, which indicates varied outcomes influenced by study design differences, participant demographics, and dietary assessment methods. However, associations for sugar-sweetened beverages and whole grains were more consistent, with lower heterogeneity.

These findings support dietary guidelines emphasizing increased plant-based foods, limited sugar-sweetened beverages, and red meat intake to combat obesity.

Conclusions

To summarize, this umbrella review highlights clear dietary patterns influencing obesity risk. Diets rich in whole grains, nuts, legumes, and fruits appear beneficial in reducing obesity, aligning with current public health recommendations. Conversely, frequent consumption of red meat and sugary beverages significantly elevates obesity risks.

Despite consistent results for key food groups, high variability across studies underscores the complexity of diet-obesity relationships, requiring cautious interpretation. Future research should explore understudied food groups such as fish, eggs, white meat, and added sugars and investigate dietary nuances, providing clearer, actionable guidance.

Ultimately, adopting balanced diets emphasizing whole foods and moderation in high-risk items could substantially reduce obesity-related health risks, enhancing public health outcomes.