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Healthy Weight: What Review Articles Indicate

In their comprehensive review of the evidence regarding the role of calcium and/or milk products in weight management, Heaney and Rafferty (2009) summarized the findings in this area of research.¹

• 31 randomized controlled trials and metabolic studies were evaluated. 17 of these demonstrated a significant benefit with respect to weight, while 15 demonstrated no difference or a non-significant benefit;
• 61 observational studies were evaluated with 45 demonstrating a significant benefit;
• The primary outcome was not weight or body composition in the majority of studies. Thus, the statistical power of the study may have been compromised. This may be one of the main reasons for inconsistencies in this area of research;
• The effect of a single factor may be relatively small in a situation that may involve several factors. However, a single factor may translate to a very significant outcome at a population-based level;
• One should expect to find no association or no difference in the absence of an appropriate control group. For example, it is believed that there is a threshold level of calcium, above which there is no further benefit with respect to weight. Therefore, it is important to have a control group that includes low calcium intake at baseline (usually < 800 mg/day).

Some highlights from a review paper that summarizes the evidence to date and the proceedings of a scientific symposium on milk products and weight management are as follows:²

• Based on the results from prospective population and cross-sectional studies, low calcium and/or milk product intake is associated with greater fat mass as well as a greater risk of weight and fat-mass gain over time;
• Results from randomized controlled trials that included weight and/or body composition as a primary outcome demonstrate that higher intakes of calcium and/or milk products facilitate weight and/or fat-mass loss in individuals whose habitual calcium intake is below recommended levels;
• Studies have shown that milk product consumption protects muscle mass during energy restriction and increases muscle mass in individuals on eucaloric diets. This is likely due to the role of milk proteins, more specifically the amino acid leucine;
• Results from randomized controlled trials support the existence of a causal relationship between calcium and/or milk product consumption and improvement in the lipid-lipoprotein profile, which may be due to improvements in abdominal adiposity;
• Mechanistic studies have demonstrated that calcium promotes fat cell apoptosis. The apoptotic effect of dietary calcium appears to be mediated in large part via the inhibition of UCP2 expression and a consequent increase in mitochondrial potential, a key regulator of apoptosis;
• The association between increased milk product consumption and healthier body weights has been attributed to several milk components, more specifically calcium;
• Milk proteins (casein and whey) may be the best explanation for the association between milk product consumption and healthier body weights due to their role in suppressing short-term food intake, increasing subjective satiety and stimulating food intake regulatory mechanisms known to signal satiation and satiety.

Keywords: healthy weight, health studies

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