When Dairy Met Weight Loss
Today’s Dietitian
By David A. Mark, PhD
Vol. 6 No. 2 p. 54

Yes, The Calcium Key: The Revolutionary Diet Discovery That Will Help You Lose Weight Faster (Zemel) and The Calcium Diet (Kaye) are in bookstores and the American Dietetic Association recommends the dairy industry’s “24/24 Milk Your Diet. Lose Weight!” meal plan on the www.eatright.org Web site, but how did it all get started? What were the initial observations, and when did the dairy industry decide to put its reputation behind a theory—that consuming 24 ounces of low-fat or fat-free dairy foods every 24 hours (hence the “24/24” promotion) can result in weight loss and fat loss?

In the latter half of the 20th century, the dairy industry was fighting a losing battle to retain its place in the American diet. From the 1950s, when total fluid milk consumption was approximately 36 gallons per person, to 2001, when it crossed to less than 23 gallons per person, the decline has been a steady 3 gallons per decade (-33% over 50 years). While an increase in cheese consumption from the mid-70s onward (thanks to pizza) partially compensated for the decline in the milk-drinking habit, the net result from 1950 to 2002 is still down for all dairy. And that is in spite of the fact that the FDA approved a health claim for calcium and bone health in 1993,2 or that low-fat milk has been outselling whole milk since 1987.1

In the late 1980s, Michael Zemel, PhD, made an observation ahead of its time—obese, African American, hypertensive subjects who were instructed to consume two servings of low-fat dairy food (yogurt) per day as part of a hypertension study finished the yearlong study with a 4.9-kilogram (10.8-pound) fat loss. This result was so out of place that Zemel left it unpublished until 2000,3 but in the interim it was a topic of interest to the dairy industry and the cadre of dairy-funded researchers working on either osteoporosis or hypertension.

One of the cardinal rules of functional food research is that it is better to have results without understanding the mechanism than to have a proposed mechanism but no results. Better still to have results and a mechanism. Because on the surface the concept sounded so contrarian—that dairy foods, long linked in consumers’ minds with fat content and weight gain, could have a beneficial role in weight management—the dairy industry and university-based research experts on calcium and health felt that a two-pronged approach (ie, strong clinical evidence and mechanism research) would be needed.

Researchers reexamined old calcium or dairy studies to look at body weight and body fat effects. Epidemiologists took another look at the Third National Health and Nutrition Examination Survey (NHANES III). As ably summarized in reviews published in 20034 and 2004,5,6 the preponderance of evidence clearly supports an inverse relationship between calcium intake and obesity and body fat content. The oldest published observation appears to be a 1984 analysis of NHANES I data, which reported a negative correlation of calcium intake with body mass.7

While this was going on, Zemel and others worked on understanding mechanism(s) of action.3,4,5,8 Briefly, increasing dietary calcium has the apparently contradictory effect of lowering the calcium concentration in fat cells (and other cells). This happens because dietary calcium suppresses the formation of calcitriol (1,25-dihydroxyvitamin D3), the active form of vitamin D. This calcium absorption-promoting hormone affects both dietary and cellular calcium uptake. When intracellular calcium is lowered in fat cells (by increasing dietary calcium), the storage of triglycerides is decreased. The consequence is lower body weight and lower percent body fat. Cell culture and animal model experiments have confirmed this effect.

Beyond the calcium mechanism, there is speculation that peptides from milk proteins, known to have angiotensin-converting enzyme (ACE) inhibitory activity, may be affecting fat metabolism, or that the branch-chain amino acids of dairy protein may help preserve muscle mass over fat during weight loss.5 Appetite may also be affected by dairy foods. A small clinical trial reported that food intake over a 24-hour period was suppressed after a dairy-containing breakfast when compared to the period following a nondairy breakfast low in calcium and vitamin D8.

Although the in vitro, animal, and population studies generally support a calcium effect and perhaps a dairy bonus, clinical trials have been a bit more equivocal. As covered in the November 2004 Today’s Dietitian article “Camp Calcium” [Vol. 6, No. 11; page 41], when 32 obese adults were fed a calorically restricted diet (decreased by 500 kilocalories per day) for 24 weeks, the third on diet alone lost 6.6 kilograms (4.8 kilograms of that was fat), the third on diet plus 800 milligrams calcium carbonate supplement lost 8.6 kilograms (5.6 kilograms of fat), and the third on diet plus three servings of dairy products lost 10.9 kilograms (7.2 kilograms of fat).6 The same researchers mention two unpublished studies in a recent review5—in these, there were no differences in body weight for dairy vs. no dairy, but the groups getting three servings of dairy foods per day lost fat and preserved lean tissue mass (muscle).

A clinical study presented by Jean Harvey-Berino, RD, MS, PhD, at the November 2004 meeting of the North American Association for the Study of Obesity also had a smaller weight change effect than the Obesity Research study. In the latest study, when 54 obese adults were divided into two groups that each underwent caloric restriction (decreased by 500 kilocalories per day) and exercise (1,000 kilocalories equivalent per week) for 24 weeks, the group that consumed three to four servings of dairy foods per day (low-fat milk and yogurt and full-fat cheese) lost 10 kilograms while the group that was restricted to one dairy serving per day and no calcium supplementation lost 9.3 kilograms. The difference in weight loss between the groups was not statistically significant (could have happened by chance).

It is fairly clear for population and intervention studies that calcium is associated with weight maintenance and weight loss, and it is possible (not proven) that dairy foods have an advantage over calcium from dietary supplements. If there is a dairy benefit, the evidence supporting it comes from studies using milk and yogurt, so it is not known whether cheese is as effective. But as low-fat dairy foods provide vitamin D, some vitamin A, and high-quality protein in addition to calcium, they can be part of a balanced diet, even one intended to help with weight management.

The dairy industry has not been shy about promoting low-fat dairy foods as part of a diet plan that will result in weight and fat loss. The National Dairy Council Web site9 has referenced fact sheets for health professionals and plenty of consumer information. Downloadable issues of the Dairy Council Digest (March 2000, July 2002, and March 2004) show a progressively confident message on dairy and weight loss. And the Milk Processor Education Program launched the “24/24 Milk Your Diet. Lose Weight!” campaign in May 2004.10

Has the dairy and weight-loss message helped the dairy industry? It is too early to tell. The last available data from the USDA’s Economic Research Service1 is for 2002. Fluid milk consumption was marginally (0.5%) lower than for 2001. But given the push to get nonnutritive carbonated beverages out of the school systems as part of antiobesity campaigns, low-fat milk may find itself the trendy beverage of the 21st century.

— David A. Mark, PhD, is president of dmark consulting LLC, a provider of research management services to functional food and dietary supplement companies.

References
1. Trends in U.S. per capita consumption of dairy products. Also: Spreadsheets. Amber Waves. United States Department of Agriculture Economic Research Service Web site. Available at: http://www.ers.usda.gov/data/foodconsumption.
2. A food labeling guide. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition Web site. Available at: http://www.cfsan.fda.gov/~dms/flg-6c.html.
3. Zemel MB, Shi H, et al. Regulation of adiposity by dietary calcium. FASEB J. 2000;14:1132-1138.
4. Parikh SJ, Yanovski JA. Calcium intake and adiposity. Am J Clin Nutr. 2003;77:281-287.
5. Zemel MB. Role of calcium and diary products in energy partitioning and weight management. Am J Clin Nutr. 2004;79(suppl):907S-912S.
6. Zemel MB, Thompson W, et al. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obesity Res. 2004;12:582-590.
7. McCarron DA, Morris CD, et al. Blood pressure and nutrient intake in the United States. Science. 1984;224:1392-1398.
8. Ping-Delfos WC, Soares MJ, Cummings NK. Acude suppression of spontaneous food intake following dairy calcium and vitamin D. Asia Pac J Clin Nutr. 2004;13(suppl):S82.
9. National Dairy Council Web site. Available at: http://www.nationaldairycouncil.org.
10. Milk Processor Education Program Web site. Available at: http://www.2424milk.com.

Book Reviews
The Calcium Key: The Revolutionary Diet Discovery That Will Help You Lose Weight Faster
By Michael Zemel, PhD, and Bill Gottlieb
John Wiley & Sons
$24.95
Michael Zemel, PhD, is the “father” of dairy and weight-loss research. The science is here, but he and coauthor Bill Gottlieb, past editor of Prevention magazine, also provide lots of practical advice about how to incorporate three servings per day of low-/no-fat dairy foods into a reduced-calorie diet. Meal plans and recipes are included.

The Calcium Diet
By Edita Kaye
The Calcium Research Institute
$22.95
Kaye has written a number of weight-loss books, including The Skinny Pill. In her new book, she stresses calcium supplements over dairy foods and provides a chapter on obesity in America.

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