Data Do Not Support Recommending Dairy Products for Weight Loss
This letter to the editor was published in the January 2005 issue of Obesity Research.
Care should be taken when interpreting the findings from any single small clinical trial, including the report by Zemel et al.1
The study reported on weight lost over 24 weeks by 32 obese individuals assigned to three different calorie-restricted diets: low dairy; high dairy; and calcium-supplemented low dairy. Each diet group had 10 or 11 subjects; this sample size is large enough to detect a difference in weight loss between the groups but too small to serve as a basis for weight loss recommendations. It is not clear whether the diets differed in any other substantial way (e.g., fiber content, glycemic load), nor are data presented to indicate how well the participants complied with the “no change in exercise” protocol or whether they achieved the prescribed 500-kcal/d deficit. The authors report mean energy intake for each group but not the change from baseline.
The high dairy product consumers lost an average of 11.07 _ 1.63 kg over 24 weeks, or _1 lb/wk, which is consistent with what might be expected based on a 500-kcal/d energy deficit 2. Mean weight loss was lower in the low-calcium (6.6 _ 2.58 kg) and high-calcium treatment groups (8.58 _ 1.60 kg) than would have been expected if the subjects maintained a 500-kcal/d deficit. This difference may have been accounted for by lack of compliance with the energy restriction or possible differences in energy expenditure, the diet composition, or the treatments themselves.
If the mechanism of action proposed by Zemel et al. for a dairy and calcium effect on weight loss holds, it raises major concerns, because it is similar to one proposed for the association between prostate cancer risk and milk consumption.3 Namely, the consumption of higher levels of calcium is thought to reduce the production of vitamin D3.1,3 Vitamin D3 action has been shown to be protective of the prostate,3 and it has been shown to inhibit fat breakdown in human fat cells in vitro.4 For this reason, caution should be exercised when making dietary recommendations regarding the consumption of additional cow’s milk.
Given these concerns, it is inappropriate to make diet recommendations based on this small exploratory study. Even if the difference in weight loss is replicable, conclusions should be limited to the conditions of the study: obese subjects on calorie-restricted diets. When calcium or dairy products are given in clinical trials (designed to look at bone health end-points) without caloric restriction, weight loss does not occur, as was clearly shown in a recent review.5
Currently, the National Dairy Council is promoting dairy consumption for weight loss in advertisements that go well beyond these study findings. These advertisements credit the inclusion of three to four servings of milk, yogurt, and cheese with producing 24 lb of weight loss without disclosing that the study participants were obese and asked to restrict calories.6
1. Zemel MB, Thompson W, Milstead A, Morris K, Campbell
P. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obes Res. 2004;12:
2. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism, 2nd ed. St. Paul, MN: West Publishing Co.; 1995.
3. Giovannucci E. Dietary influences of 1,25(OH)2 vitamin D in relation to prostate cancer: a hypothesis. Cancer Causes Control. 1998;9:567– 582.
4. Zemel MB, Shi H, Greer B, DiRienzo D, Zemel PC. Regulation of adiposity by dietary calcium. FASEB J. 2000;14: 1132–1138.
5. Barr SI. Increased dairy product or calcium intake: is body weight or composition affected in humans? J Nutr. 2003;133:245S–8S.
6. National Dairy Council. Healthy weight with dairy. http://www.nationaldairycouncil.org/healthyweight/DMI_graphic1_041204.pdf. Accessed May 18, 2004.