Association of dairy products consumption with risk of obesity in children and adults: a meta-analysis of mainly cross-sectional studies

Abstract

Purpose

The association of dairy products consumption with risk of obesity remains controversial. Therefore, we reviewed and quantitatively synthesized the evidence from observational studies with a meta-analysis.

Methods

A literature search was performed in relevant databases. Random-effects model was used to pool odds ratios with 95% confidence intervals. Dose–response relationship was assessed by restricted cubic spline model.

Results

Seventeen studies for total dairy products and 16 studies for milk with risk of obesity were eligible. The pooled odds ratios (95% confidence intervals) of obesity for the highest versus lowest category of total dairy products consumption were 0.54 (0.38–0.77) in children, 0.75 (0.69–0.81) in adults, and 0.74 (0.68–0.80) for both. Evidence of a nonlinear relationship was found (P_{for nonlinearity} = .009). Milk consumption was also associated with risk of obesity [0.81 (0.75–0.88)] both in children [0.87 (0.80–0.95)] and in adults [0.77 (0.68–0.87)], and a linear relationship (P_{for nonlinearity} = .598) suggested that risk of obesity decreased by 16% [0.84 (0.77–0.92)] for every 200 g/d increment of milk consumption.

Conclusions

This meta-analysis indicates that dairy products consumption may be associated with a decreased risk of obesity. This association may be of public health significance.

Introduction

Obesity has now become a rapidly growing threat to public health, and its comorbidities include a number of chronic diseases, such as coronary heart disease, hypertension and stroke, cancer, diabetes, and pulmonary diseases, including sleep apnea, and so on [1]. Current evidence indicates that obesity can be affected by genetic and environmental factors, such as changes in physical activity and dietary pattern [2], [3]. And dairy products, a good source of calcium, branched chain amino acids, conjugated linoleic acid, protein, and vitamin D, have been hypothesized to reduce risk of obesity [4], [5].

A systematic review by Louie et al. [6] found that the evidence for the protective effect of dairy products against risk of overweight and/or obesity was suggestive but not consistent, and it was difficult to make firm conclusions. In contrast, a recently published meta-analysis of population in children by Lu et al. [7] suggested that dairy products were inversely and longitudinally associated with risk of overweight and/or obesity. At present, none meta-analysis has estimated the pooled odds ratio (OR) of obesity in relation to dairy products based on all relevant observational studies and in population of adults, and the dose–response relationship is uncertain. Observational studies on this association have reported inconsistent results: some studies found no association between them [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], whereas other studies observed negative associations [8], [13], [18], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31]. Therefore, considering the considerable public health consequences, the role of dairy products on body weight still needs to be fully explored.

Given individual study might be underpowered to detect the effect due to the relatively small number of participants, we perform a meta-analysis of observational studies to further assess the association of dairy products with risk of obesity and evaluate the possible dose–response relationship.