MINNEAPOLIS — Dropping dairy products from calorie counting weight-loss diets could backfire, according to a new study to be published in the April issue of the International Journal of Obesity. The study reveals that yogurt and other dairy products may help turn up the body's fat-burning ability, making it easier to lose fat while maintaining lean muscle.
The study was submitted by lead researcher Michael Zemel, Ph.D., professor of nutrition at the University of Tennessee. His work found that individuals who included light yogurt as part of their weight loss plan lost significantly more weight compared with others who simply reduced calories.
The yogurt eaters lost 22% more weight, or an average of 14 pounds; 66% more body fat; and 81% more trunkal (stomach) fat during the 12-week study.
"The results are impressive," according to an editorial discussing the study in the same issue. The editorial also notes the research was important because losing fat while "protect(ing) lean body mass is essential for the development of appropriate dietary recommendations."
Dr. Zemel and colleagues at the University of Tennessee studied the impact of adding yogurt to a reduced-calorie diet on 34 healthy obese adults who were randomly assigned to one of two diet groups.
The yogurt group consumed about 1,100 mg of calcium each day, which included three servings of Yoplait Light yogurt. The control group consumed a low calcium diet with only one serving of dairy per day, a reflection of the typical American diet, which is chronically low in calcium.
All subjects in the study received an individualized diet plan that provided 500 fewer calories than their usual daily intake. Body weight and blood pressure were recorded weekly, and total body composition was assessed before and after the 12-week intervention by dual-energy X-ray absorptiometry.
"Not only did yogurt help the study participants lose more weight,-they were about twice as effective at maintaining lean muscle mass," Dr. Zemel said. "This is a critical issue when dieting; you want to lose fat, not muscle. Muscle helps burn calories, but it is often compromised during weight loss."
The participants who included yogurt in their diets also lost 81% percent more fat in the stomach area, which is the most dangerous type of fat. The calcium-rich diet helped the participants lose more than an inch around their waist, representing about a six-fold greater decrease in waist circumference.
"Successful weight maintenance involves small lifestyle changes that can be easily done on a daily basis," said Dr. James Hill of the University of Colorado, who is the lead researcher for the National Weight Control Registry and author of the recently published The Step Diet Book. "The science connecting yogurt and weight loss is very encouraging, and what could be easier than including yogurt in your daily routine?"
Dr. Zemel has been a pioneer in this emerging area of research examining the relationship between calcium and weight management. He was the first to discover that small changes in the calcium levels of fat cells alter signals within the cell that control the production and breakdown of fat.
His previous studies have found that in a reduced-calorie diet, as calcium intake goes up, weight and body fat go down. A diet low in calcium appears to stimulate the production of fat-producing enzymes and decreases the activity of enzymes that break down fat, Dr. Zemel said.
"The moral of the calcium story is to not dump dairy when you're dieting," he said. "Not only is it critical to keep your calcium levels high so you won't lose bone density, it will also help you maintain your muscle mass and increase your fat loss. A diet rich in low-fat dairy foods, like yogurt, can help make your weight lost efforts easier."