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Dietary calcium appears to play a pivotal role in the regulation of
energy metabolism and obesity risk. High calcium diets attenuate body fat
accumulation and weight gain during periods of over-consumption of an
energy-dense diet and to increase fat breakdown and preserve metabolism
during caloric restriction, thereby markedly accelerating weight and fat
loss. This effect is mediated primarily by circulating calcitriol, which
regulates adipocyte intracellular Ca(2+). Studies of human adipocyte
metabolism demonstrate a key role for intracellular Ca(2+) in regulating
lipid metabolism and triglyceride storage, with increased intracellular
Ca(2+) resulting in stimulation of lipogenic gene expression and lipogenesis
and suppression of lipolysis, resulting in adipocyte lipid filling and
increased adiposity. Moreover, the increased calcitriol produced in response
to low calcium diets stimulates adipocyte Ca(2+) influx and, consequently,
promotes adiposity, while higher calcium diets inhibit lipogenesis, promote
lipolysis, lipid oxidation and thermogenesis and inhibit diet-induced
obesity in mice. Notably, dairy sources of calcium exert markedly greater
effects in attenuating weight and fat gain and accelerating fat loss. This
augmented effect of dairy products versus supplemental calcium has been
localized, in part, to the whey fraction of dairy and is likely due to
additional bioactive compounds, such as angiotensin converting enzyme (ACE)
inhibitors in dairy, as well as the rich concentration of branched chain
amino acids, which act synergistically with calcium to attenuate adiposity;
however, these compounds do not fully account for the observed effects, as
whey has significantly greater bioactivity than found in these compounds.
These concepts are confirmed by epidemiological data as well as recent
clinical trials which demonstrate that diets which include at least three
daily servings of dairy products result in significant reductions in body
fat mass in obese humans in the absence of caloric restriction and markedly
accelerates the weight and body fat loss secondary to caloric restriction
compared to low dairy diets. These data indicate an important role for dairy
products in both the ability to maintain a healthy weight and the management
of overweight and obesity.
Reference:
J Am Coll Nutr.
2005 Dec;24(6 Suppl):537S-46S. |