Specifically, the calcium in dairy products helps people lose weight or
keep their weight down.
In a recent study at the University of Tennessee, overweight people who ate three servings of yogurt daily lost 22% more weight, 61% more body fat and 81% more abdominal fat over 12 weeks than those who ate the same number of calories but didn't consume any dairy. Muscle helps burn calories, says study author Michael Zemel. This study shows that when you eat a diet high in dairy foods, you lose more fat and protect more muscle.
Michael Zemel is the director of the University of Tennessee's Nutrition Institute. Apparently, dietary calcium is the important factor, but "Zemel's research suggests that [calcium] pills aren't a perfect substitute for the complex package of nutrients found in milk". Not all dairy products "make the list" of diet-friendly foods either; Cream cheese, sour cream, cottage cheese and ice cream are "either poor sources of calcium or too high in fat to include".
The above quotes are from an article entitled Holy Cow! in the July 2002 issue of Reader's Digest and a short followup piece in the July 2003 issue. Although the RD articles are not online, the following may be of interest:
Calcium may become a dieter's best friend
National Dairy Council Press Release, Nov. 17, 1999
The Doctor Will See You Now