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Vitamin D speeds up fat breakdown during weight loss

Overweight women on a weight-loss diet lose fat more quickly the more vitamin D they have in the blood, and the more vitamin D their food contains. Researchers at the Spanish Complutense University of Madrid published an article on this in the British Journal of Nutrition. It also looks as though vitamin D preserves fat-free mass as well during weight loss.

The Spanish results, as the researchers emphasize, are preliminary. They are based on the first two weeks of their experiment which involved sixty overweight women aged between 20 and 35 years.

The researchers divided the women to start with in two large groups: those with a lot and those with little vitamin D in their blood. Then the researchers put the women in both groups on two different diets. One diet consisted mainly of fruit and vegetables and contained less than 3 micrograms of vitamin D per day; the other diet consisted of mainly grains in the form of special bars from the factories of the sponsor Kellogg Espana.

Although the dairy industry is understandably fond of the theory that calcium reduces obesity by blocking vitamin D in the body, other researchers claim to have found evidence that a higher vitamin D level actually reduces the chance of overweight. These indications were the reason behind the Spanish research.

The tables below show what happened to the dieting women in the two-week period. All groups ate about the same amount of kilocalories.

Vitamin D speeds up fat breakdown during weight loss

Above are the results for the women with little vitamin D [= 25(OH)D] in their blood. There are no surprises here. Below, however, in the table with the results for the women with a high level of vitamin D in their blood, it's a different story.

Vitamin D speeds up fat breakdown during weight loss

"The present results, although they have been obtained in a small sample size and in a short period of time, suggest that women with a better vitamin D status respond more positively to hypocaloric diets and lose more body fat", the researchers conclude.

We stress: "…in a small sample size and in a short period of time." But we'll be keeping an eye on the matter.

Br J Nutr. 2008 Aug;100(2):269-72.