HEALTH NEWS

Study Title:

Higher Protein and Higher Dairy Intake Support Healthy Weight Loss

Study Abstract

Weight loss can have substantial health benefits for overweight or obese persons; however, the ratio of fat:lean tissue loss may be more important. We aimed to determine how daily exercise (resistance and/or aerobic) and a hypoenergetic diet varying in protein and calcium content from dairy foods would affect the composition of weight lost in otherwise healthy, premenopausal, overweight, and obese women. Ninety participants were randomized to 3 groups (n = 30/group): high protein, high dairy (HPHD), adequate protein, medium dairy (APMD), and adequate protein, low dairy (APLD) differing in the quantity of total dietary protein and dairy food-source protein consumed: 30 and 15%, 15 and 7.5%, or 15 and <2% of energy, respectively. Body composition was measured by DXA at 0, 8, and 16 wk and MRI (n = 39) to assess visceral adipose tissue (VAT) volume at 0 and 16 wk. All groups lost body weight (P < 0.05) and fat (P < 0.01), however, fat loss during wk 8–16 was greater in the HPHD group than in the APMD and APLD groups (P < 0.05). The HPHD group gained lean tissue with a greater increase during 8–16 wk than the APMD group, which maintained lean mass and the APLD group, which lost lean mass (P < 0.05). The HPHD group also lost more VAT as assessed by MRI (P < 0.05) and trunk fat as assessed by DXA (P < 0.005) than the APLD group. The reduction in VAT in all groups was correlated with intakes of calcium (r = 0.40; P < 0.05) and protein (r = 0.32; P < 0.05). Therefore, diet- and exercise-induced weight loss with higher protein and increased dairy product intakes promotes more favorable body composition changes in women characterized by greater total and visceral fat loss and lean mass gain.

From press release:

New research suggests 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.

The study, published in the September issue of the Journal of Nutrition, and partly funded by Dairy Farmers of Canada,* 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.

According to the researchers, 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.

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

"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," says 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."

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," says Josse.

"A very important point is that these changes were not captured by simple measures of body weight or body mass index, which are the most commonly used measures of dietary 'success'" adds Stuart Phillips, a professor in the Department of Kinesiology. "These women also got fitter and stronger, which greatly reduces their risk of disease."

Study Information

Andrea R. Josse, Stephanie A. Atkinson, Mark A. Tarnopolsky, and Stuart M. Phillips.
Increased Consumption of Dairy Foods and Protein during Diet- and Exercise-Induced Weight Loss Promotes Fat Mass Loss and Lean Mass Gain in Overweight and Obese Premenopausal Women
Journal of Nutrition
2011 September
Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, ON, Canada.