Best available evidence clearly indicates that calcium and vitamin D are important players in the regulation of body weight.
It is their presumed effect on weight loss, which is less tangible. Calcium and vitamin D can probably best fight obesity by preventing weight gain.
Curtin University Associate Professor Mario Soares and colleagues reviewed the available literature on randomised clinical trials, which manipulated calcium and vitamin D intake for weight loss. Their insightful view on the complex physiology behind calcium and vitamin D effects on energy metabolism was recently published in Obesity Reviews.
“As a nation we have poor calcium intake and a large section of our population is vitamin D deficient, despite [Australia] being a sundrenched country,” says Dr Soares.
Calcium intake helps fight unwanted storage of fat in various ways. Absorbed into the blood stream, it burns fat through fat oxidation—remaining within the gastrointestinal tract, it binds fat and stimulates faecal fat excretion.
Vitamin D only indirectly increases fat metabolism by enhancing calcium absorption. Its real impact on body weight control is more likely to come from its ability to increase insulin sensitivity, thereby reducing hunger and diminishing food intake.
Despite these beneficial influences of both nutrients on body fat, their supplementation in weight loss trials did not lead to the anti-obesity effects researchers had hoped for.
Dr Soares says, “As soon as you perturb somebody’s energy input, the metabolic mechanisms that set in are essentially the ones that prevent weight loss. The body wants to regain weight to its original set point.”
In physiological terms, obesity is a “state of positive energy with an imbalance in how much is ingested and how much is expended”. Over time, this allows weight to accrue.
Dr Soares believes public health will gain from the early detection of such energy imbalances to prevent weight gain.
The sensitivity of current methods needs to be improved and analytical outcomes reflecting the human energy balance need to be optimised to pick up those small but essential changes, which initiate weight gain.
Dr Soares’s suggests aiming for small amounts of healthy weight loss, which can be maintained over a long period of time.
His research has shown that weight loss with a diet inclusive of calcium rich dairy products may initially be marginal, but it maintains healthy bones and muscles, keeps energy expenditure high and redistributes fat away from the waist.