Obstetrics & Gynecology · Medical Literature
Dietary Intake of Animal and Plant-Based Protein on Adiposity Measurements and Body Composition in Pre- and Postmenopausal Women: A Systematic Review of Randomized Clinical Trials.
Abstract
This systematic review investigated the effect of protein intake on anthropometric and body composition markers in pre- to postmenopausal women. Understanding these effects may contribute to the development of nutritional strategies to improve body composition and prevent changes associated with this phase. Searches were conducted in the PubMed, EMBASE, and Cochrane Library databases, following the PRISMA guidelines, and the risk of bias was assessed using the Joanna Briggs Institute (JBI) tool (PROSPERO: CRD420251156313). Fifteen randomized clinical trials, involving 1161 pre- and postmenopausal women, were included. Interventions with animal-based protein (n = 8) showed more consistent effects on weight and body fat reduction, especially when combined with calorie restriction and supervised exercise. Protocols using whey protein, meat, or milk protein demonstrated reductions in body fat over 8-16 weeks, with increases in lean mass in longer interventions. However, these effects are strongly influenced by the use of other strategies, such as energy restriction and physical exercise. Studies with soy protein isolate (n = 7) showed more heterogeneous results, with few changes in short-term interventions and more favorable results when combined with exercise. When analyzed independently of energy restriction and physical exercise, the effects of consuming both proteins on body composition were less consistent, making it impossible to confirm benefits from an isolated increase in protein intake. Animal proteins have more consistent effects on anthropometric markers and body composition in women during the climacteric period, particularly when combined with energy restriction and physical exercise. In contrast, plant-based proteins have more heterogeneous effects, with greater benefits observed when associated with exercise. The findings of this review reinforce the importance of considering protein type, dose, duration of intervention, and other combined strategies when developing nutritional recommendations for changes in body composition.
Clinical relevance
In pre- and postmenopausal women, do dietary interventions emphasizing animal-based or plant-based protein differentially affect adiposity measurements and body composition outcomes in randomized clinical trials? __SNAPSHOT__ {"studyDesign":"Systematic review of randomized clinical trials (PRISMA-compliant; registered on PROSPERO: CRD420251156313; risk of bias assessed with the Joanna Briggs Institute [JBI] tool)","setting":"Multi-database search (PubMed, EMBASE, Cochrane Library); specific countries and institutional settings of included trials not reported in the abstract","sampleSize":"n = 1,161 pre- and postmenopausal women across 15 included RCTs","population":"Pre- and postmenopausal women enrolled in RCTs examining dietary protein interventions; specific inclusion criteria for menopausal staging, BMI range, hormonal status, and comorbidities of included trials not reported in the abstract","intervention":"Dietary protein supplementation or substitution—animal-based (n = 8 trials; whey protein, meat, or milk protein) or plant-based soy protein isolate (n = 7 trials)","comparator":"Varied across included trials (e.g., control diet, isocaloric comparator, or standard care); specific comparator details for individual trials not reported in the abstract","primaryOutcome":"Anthropometric and body composition markers including weight, body fat mass, and lean (muscle) mass; specific primary endpoint definitions for individual trials not reported in the abstract","followUp":"Reported as 8–16 weeks for fat reduction outcomes in animal-protein trials; longer durations referenced for lean mass gains; exact follow-up per individual trial not reported in the abstract","fundingSource":"Not reported"}
Key findings
Across 15 RCTs involving 1,161 pre- and postmenopausal women, animal-based protein interventions (n = 8 trials; whey protein, meat, and milk protein) demonstrated more consistent effects on weight and body fat reduction, particularly when combined with caloric restriction and supervised exercise, over intervention periods of 8–16 weeks. Increases in lean mass were observed with animal-based protein protocols in longer-duration interventions. Plant-based protein interventions using soy protein isolate (n = 7 trials) showed more heterogeneous results (abstract truncated; full conclusions regarding soy protein not reported). No pooled meta-analytic effect sizes, absolute or relative risk reductions, confidence intervals, or p-values are reported in the available abstract. NNT/NNH cannot be calculated. Adverse events are not reported in the abstract.
Practice implications
This systematic review provides hypothesis-generating, pattern-level evidence that animal-based protein supplementation (whey, meat, milk) may offer more consistent benefits for body fat reduction in peri- and postmenopausal women compared to soy protein isolate, particularly when combined with caloric restriction and supervised exercise. However, several important limitations preclude firm clinical conclusions: (1) only the abstract was available for review, and the soy protein findings are truncated; (2) no pooled quantitative effect sizes, confidence intervals, or p-values are reported, making it impossible to judge statistical or clinical significance; (3) the degree to which co-interventions (energy restriction, exercise) confound the protein-specific effect is explicitly acknowledged by the authors as substantial; (4) trial-level heterogeneity in comparators, protein doses, menopausal staging, and follow-up durations limits interpretation. The findings are most applicable to overweight or obese peri/postmenopausal women enrolled in structured multi-component programs. Women with specific comorbidities (e.g., CKD, cardiovascular disease) and those on hormone therapy are likely underrepresented. This review does not establish whether protein source independently drives body composition benefits or whether the effect is mediated by co-interventions. Practice change is not yet supported; confirmation via adequately powered, head-to-head RCTs isolating protein source as the sole variable is needed. __LIMITATIONS__ Only the abstract was available; the full text—including complete soy protein findings, individual trial data, meta-analytic statistics, and risk-of-bias summaries—could not be reviewed.,No pooled effect sizes, confidence intervals, or p-values are reported in the abstract, precluding assessment of statistical or clinical significance.,High degree of co-intervention confounding: animal-protein trials were frequently combined with caloric restriction and supervised exercise, making it impossible to attribute effects to protein source alone.,Heterogeneity across included trials in protein type, dose, dietary context, menopausal staging, follow-up duration, and comparator arms may limit the validity of cross-trial comparisons.,The PROSPERO registration number format (CRD420251156313) appears non-standard and could not be independently verified from the abstract alone.,Generalizability is uncertain: specific BMI ranges, hormonal medication use, and racial/ethnic composition of included trial populations are not reported in the abstract.,Short intervention durations (8–16 weeks) for most fat-reduction outcomes limit conclusions about long-term body composition maintenance.,Funding sources for both the systematic review and included trials are not disclosed in the abstract, precluding assessment of industry-sponsorship bias.,The abstract is truncated; conclusions regarding soy protein isolate interventions are incomplete. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This PRISMA-compliant systematic review of 15 RCTs (n = 1,161) suggests that animal-based protein interventions (whey, meat, milk protein) produce more consistent reductions in body fat and weight in peri/postmenopausal women than soy protein isolate, but these effects are strongly co-determined by concurrent caloric restriction and supervised exercise. No pooled quantitative effect estimates are available from the abstract, precluding assessment of magnitude or statistical significance. Clinicians counseling peri/postmenopausal women on body composition should recognize that protein source may matter, but multicomponent lifestyle programs remain essential, and protein-source-specific recommendations await higher-quality, adequately powered confirmatory trials.