Angelo Tremblay and his team at Universit?© Laval's Faculty of Medicine made the discovery in a 15-week weight loss program they conducted on obese women. The participants consumed on average less than 600 mg of calcium per day, whereas recommended daily intake is 1000 mg. In addition to following a low calorie diet, the women were instructed to take two tablets a day containing either a total of 1200 mg of calcium or a placebo. Those who took the calcium tablets lost nearly 6 kg over the course of the program, the researchers found, compared to 1 kg for women in the control group.
"Our hypothesis is that the brain can detect the lack of calcium and seeks to compensate by spurring food intake, which obviously works against the goals of any weight loss program," said Angelo Tremblay, holder of the Canada Research Chair in Environment and Energy Balance. "Sufficient calcium intake seems to stifle the desire to eat more," he added.
Consuming sufficient calcium is therefore important to ensuring the success of any weight loss program. According to the researcher, over 50% of obese women who come to the clinic run by his research team do not consume the recommended daily intake.
Professor Tremblay and his team have studied the link between calcium and obesity for several years. Their first findings, published in 2003, revealed that women who consumed diets poor in calcium had more body fat, bigger waistlines, and higher bad cholesterol levels than those who consumed moderate or large amounts of calcium. A second study showed that the more people reduced their consumption of dairy products over the six-year period examined, the more weight and body fat they gained and the bigger their waistlines grew. In 2007, Angelo Tremblay and his team established a direct link between calcium and a lower cardiovascular risk profile among dieters.
In addition to Angelo Temblay, this study was co-authored by Genevi ve Major, Francine Alarie, and Jean Dor?©.
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In this study, he and his colleagues show that CLOCK works in balance with SIRT1 to direct activity in a cell pathway by which metabolic proteins send signals called the NAD+ salvage pathway. In turn, a key protein in that pathway, NAMPT, helps control CLOCK levels, creating a tightly regulated codependency between our circadian clock and metabolism.
"When the balance between these two vital processes is upset, normal cellular function can be disrupted," Sassone-Corsi said. "And this can lead to illness and disease."
The findings suggest that proper sleep and diet may help maintain or rebuild this balance, he said, and also help explain why lack of rest or disruption of normal sleep patterns can increase hunger, leading to obesity-related illnesses and accelerated aging.
The specific interaction between CLOCK and SIRT1 and the NAD+ salvage pathway also presents a starting point for drug development aimed at curbing cell dysfunction and death, thereby helping to solve major medical problems such cancer and diabetes.
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