QUEBEC CITYCertain probiotics may help women lose weight and keep it off, according to a recent study published in the British Journal of Nutrition by a team of Université Laval researchers.

Studies have already demonstrated that the intestinal flora of obese individuals differs from that of thin people. That difference may be due to the fact that a diet high in fat and low in fiber promotes certain bacteria at the expense of others. Université Laval professor Angelo Tremblay and his team tried to determine if the consumption of probiotics could help reset the balance of the intestinal microbiota in favor of bacteria that promote a healthy weight.

To test their hypothesis, researchers recruited 125 overweight men and women. The subjects underwent a 12-week weight-loss diet, followed by a 12-week period aimed at maintaining body weight. Throughout the entire study, half of the participants swallowed two pills daily containing probiotics from the Lactobacillus rhamnosus family, while the other half received a placebo.

After the 12-week diet period, researchers observed an average weight loss of 4.4 kg (9.7 lbs) in women in the probiotic group and 2.6 kg (5.7 lbs) in the placebo group. However, no differences in weight loss were observed among males in the two groups.

"We don't know why the probiotics didn't have any effect on men," Tremblay said . "It may be a question of dosage, or the study period may have been too short."

After the 12-week maintenance period, the weight of the women in the placebo group had remained stable, but the probiotic group had continued to lose weight, for a total of 5.2 kg (11.5 lbs) per person. In short, women consuming probiotics lost twice as much weight over the 24-week period of the study. Researchers also noted a drop in the appetite-regulating hormone leptin in this group, as well as a lower overall concentration of the intestinal bacteria related to obesity.

According to Tremblay, probiotics may act by altering the permeability of the intestinal wall. By keeping certain proinflammatory molecules from entering the bloodstream, they might help preventing the chain reaction that leads to glucose intolerance, type 2 diabetes, and obesity.

The Lactobacillus rhamnosus strain used in this study belongs to Nestlé, which uses it in certain yogurts it makes for the European market, but Tremblay believes that the probiotics found in dairy products in North America could have a similar effect to the Nestlé strain. He stresses, however, that the benefits of these bacteria are more likely to be observed in a favorable nutritional context that promotes low fat and adequate fiber intake.

The global probiotics market will likely hit $24 billion by 2017 due to rising levels of health consciousness and the aging baby boomer population. Probiotic chocolates, ice creams and baked products are expected to enjoy the largest market share.