Does eating unprocessed red meat lead to obesity?

Consumption of unprocessed red meat (URM) shows no significant effect on weight gain, obesity, or related metabolic conditions, according to the results of a systematic review and meta-analysis.

“Although observational data are equivocal regarding the association of URM with obesity, our study did not indicate that the randomized controlled trials (RCTs) and randomized crossover trials (RCOs) that tested URM consumption adversely impacted weight gain, obesity, or related metabolic conditions in adults,” the investigators said.

In this study, questions were created using the populations, interventions, controls, and outcomes (PICO) framework to search seven databases from 29 July 2020 to 21 August 2020. Two reviewers screened a total of 5,630 references independently. Of these, 24 studies met the eligibility criteria.

The investigators calculated the pooled effect sizes using a random-effects model and estimated the variance of the true effect sizes using the DerSimonian-Laird estimator. They also published an interactive dashboard to provide transparent analysis and data presentation.

All 95 percent confidence intervals (CIs) for unfiltered pooled effect sizes included 0, which showed no significant effect of URM consumption. Similar results were noted for other outcome measures for either RCTs or RCOs. [Obesity 2025;33:1627-1636]

“We found no significant effect of URM for BMI, body weight, or percent body fat based on unfiltered pooled effect sizes,” the investigators said.

In sensitivity analysis that filtered the largest positive effect size from each study, only minor changes to the 95 percent CI were noted, and this did not lead to meaningful changes in the results. Likewise, filtering for the largest negative effect size from each study yielded the same result, except for low-density lipoprotein cholesterol (LDL-C) in the RCTs (95 percent CI, ‒0.43 to ‒0.06).

“Filtered pooled effect size analysis showed a slight adverse effect of URM for total cholesterol and LDL-C,” the investigators said.

“Our findings can be considered in the generation of evidence-based guidelines to promote a healthy weight in adulthood and may help clinicians in weighing the merits and drawbacks of the use of URM for patients,” they added.

Recommendations

Clinicians are often divided regarding the recommendation of meat consumption in dietary guidelines despite its high-quality protein content. [https://www.dietaryguidelines.gov/; J Nutr 2020;150:663-671; Nutr Bull 2016;41:135-141]

The guidelines by NutriRECS based on four systematic reviews do not recommend changes in URM consumption in adults. Other systematic reviews also suggest that the association of URM with diseases is weak and of low certainty. [Ann Intern Med 2019;171:756-764; Ann Intern Med 2019;171:703-710; Ann Intern Med 2019;171:721-731]

In contrast, the role of URM in health remains controversial. Such discrepancy is potentially due to the inclusion of observational studies, which are not suitable to show causality, and the reliance on subjective dietary self-reports, which may be biased. [Int J Obes (Lond) 2015;39:1109-1113; Am J Physiol Endocrinol Metab 2001;281:E891-E899]

“It is also possible that URM consumption in some situations is linked with a lifestyle of a diet that is higher in energy content,” the investigators said. “This ‘guilt by association’ may mistakenly lead to conclusions regarding obesogenic properties of URM.”

This concern was addressed by focusing on RCTs and RCOs, which did not show URM as a risk factor for weight gain, obesity, or adverse lipid profile.

“Longer studies may be needed for observing obesity development in case the effect of URM on weight gain is small and needs a much longer time to express,” the investigators said.