A higher-protein, lower-carbohydrate energy-restricted diet has a major positive impact on body composition, trimming belly fat and increasing lean muscle, particularly when the proteins come from dairy products, according to a new research.

The study compared three groups of overweight and obese, but otherwise healthy, premenopausal women. Each consumed either low, medium or high amounts of dairy foods coupled with higher or lower amounts of protein and carbohydrates.

The women exercised seven days per week for four months, a routine that included five days of aerobic exercise and two days of circuit weightlifting.

The researchers said that there were identical total weight losses among the groups, but the higher-protein, high-dairy group experienced greater whole-body fat and abdomen fat losses, greater lean mass gains and greater increases in strength.

According to the researchers, the tissue composition, exclusively fat, of the weight the women lost has profound implications for longer-term health.

“One hundred per cent of the weight lost in the higher-protein, high-dairy group was fat. And the participants gained muscle mass, which is a major change in body composition,” said Andrea Josse, lead author of the study and a graduate student in the Department of Kinesiology at McMaster University.

“The preservation or even gain of muscle is very important for maintaining metabolic rate and preventing weight regain, which can be major problem for many seeking to lose weight,” added Ms. Josse.

Researchers found the lower-protein, low-dairy group lost about a pound and half of muscle whereas the lower-protein, medium dairy group lost almost no muscle. In marked contrast, the higher-protein, high-dairy group actually gained a pound and half of muscle, representing a three-pound difference between the low- and high-dairy groups.

On top of the muscle mass differences, the higher-protein, high-dairy group lost twice as much belly fat than the lower-protein, low-dairy group.

“Fat in the abdomen is thought to be especially bad for cardiovascular and metabolic health, and it seems-according to what we found in this study-increasing calcium and protein in the diet may help to further promote loss of fat from the worst storage area in the body,” said Ms. Josse.

The study has been published in the Journal of Nutrition.