Abstract
Background/Aims: A meta-analysis of randomized controlled trials (RCTs) was performed to investigate the effects of dairy food or supplements during energy restriction on body weight and composition in 18–50-year-old. Methods: RCTs ≥ 4 weeks comparing the effect of dairy consumption (whole food or supplements) with control diets lower in dairy during energy restriction on body weight, fat and lean mass were identified by searching MEDLINE, EMBASE, Pubmed, Cochrane Central and World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) until March 2016. Reports were identified and critically appraised in duplicate. Data were pooled using random-effects meta-analysis. Chi2- and I2-statistics indicated heterogeneity. Dose effect was assessed using meta-regression analysis. GRADE guidelines were used to rate the quality (QR) of the evidence considering risk of bias, inconsistency, indirectness, imprecision, publication bias and effect estimates. Results: 27 RCTs were reviewed. Participants consumed between 2 and 4 standard servings/day of dairy food or 20–84 g/day of whey protein compared to low dairy control diets, over a median of 16 weeks. A greater reduction in body weight (−1.16 kg [−1.66, −0.66 kg], p < 0.001, I2 = 11%, QR = high, n = 644) and body fat mass (−1.49 kg [−2.06, −0.92 kg], p < 0.001, I2 = 21%, n = 521, QR = high) were found in studies largely including women (90% women). These effects were absent in studies that imposed resistance training (QR = low-moderate). Dairy intake resulted in smaller loss of lean mass (all trials pooled: 0.36 kg [0.01, 0.71 kg], p = 0.04, I2 = 64%, n = 651, QR = moderate). No between study dose-response effects were seen. Conclusions: Increased dairy intake as part of energy restricted diets resulted in greater loss in bodyweight and fat mass while attenuating lean mass loss in 18–50-year-old adults. Further research in males is needed to investigate sex effects.
Highlights
Obesity is a global epidemic, with significant health and socio-economic costs [1]
Studies were excluded if: they involved multi-component interventions where the effect of dairy could not be distinguished from other components (e.g., another dietary factor added to the dairy, but not to the control, intervention; if the same additional component was added to both dairy and control interventions, the research report was included); used a cross-over study design that do not permit return to equal baseline following body weight/composition changes; used another dairy product or component as comparison; included participants with a disease condition associated with muscle wasting (e.g., human immunodeficiency virus (HIV), cancer, muscular dystrophy); included participants who were pregnant or breastfeeding; or were not available in English language
A total of 27 studies satisfied the selection criteria and were included in the systematic literature review equating to a total of 29 comparisons that included 1278 participants
Summary
Overweight and obesity are major risk factors for non-communicable diseases such as cardiovascular disease, diabetes, musculoskeletal disorders and some cancers [1]. The critical necessity to identify effective strategies to reduce and maintain a healthy body weight. Dairy in the diet may be an important modifiable factor for managing a healthy body weight and composition due to its rich source of nutrients and bioactive compounds. Dairy contains calcium which may increase faecal fat excretion [2]; protein (casein and whey) and their peptide derivatives that promote muscle protein synthesis (hypertrophy) [3] and regulate appetite [4]; and fatty acids (medium-chain triacylglycerols (MCT) and conjugated linoleic acid (CLA)) that affect energy balance through reduced de novo lipogenesis, increased fat oxidation and regulating appetite [4,5]. Evidence from observational studies suggests a protective effect of dairy food consumption on overweight and obesity risk [6]
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