Trial Information

Obesity is associated with sub-clinical chronic oxidative and inflammatory stress, both of
which are major contributors to obesity-associated co-morbidities. Calcitriol (1,
25-(OH)2-D3) regulates adipocyte lipid metabolism, while dietary calcium inhibits obesity by
suppression of calcitriol. We have recently shown calcitriol to increase oxidative stress
and to stimulate the expression and release of inflammatory cytokines, while inhibiting the
expression and release of anti-inflammatory cytokines. We have also shown that inhibition
of calcitriol with high calcium diets decreases both adipose tissue and systemic oxidative
and inflammatory stress in a mouse model of obesity. Moreover, dairy exerted a greater
effect on both oxidative and inflammatory stress. These mice also exhibited significant
reductions in adiposity, which could lead to confounding, as this reduction will
independently reduce oxidative and inflammatory stress. However, the supporting
cellular/mechanistic data indicate an effect which is independent of adiposity reduction.
Consequently, we propose that low calcium diets exacerbate oxidative and inflammatory stress
and that high dairy diets can attenuate both independently of changes in adiposity, thereby
significantly reducing the risk of obesity-associated co-morbidities. Accordingly, the
objective of this study is to determine the acute effects of a dairy-rich diet on oxidative
and inflammatory stress in overweight and obese subjects in the absence of any changes in
adiposity.

Twenty subjects (10 obese and 10 overweight) will undergo a randomized crossover study of
low dairy and high dairy eucaloric diets. Each dietary period will be four weeks, and the
two dietary periods will be separated by a four-week washout period. Primary outcomes will
be circulating indices of oxidative stress and of inflammation. Secondary outcomes include
blood pressure, circulating glucose, insulin, lipids, calcium-regulatory hormones and body
composition.