Taking supplements or eating yogurt that includes one of two new strains of probiotics may help reduce body fat by as much as 4 percent, even if you don't change your diet or exercise. That's the conclusion of a new study from the University of Manitoba, which found that people who ate yogurt that contained two novel strains of probiotics (not yet found in commercial products) every day experienced a boost in metabolism and a body fat drop of up to 4 percent in a remarkable six weeks. What's more, most of the weight lost was belly fat, which is more harmful to heart health than other forms of body fat. How can healthy bacteria cause such rapid, significant weight loss? Lead researcher Peter Jones explains that these strains of probiotics block bile salts, which help the intestines absorb fat from food. "Without proper bile-salt concentrations, fats that would otherwise be absorbed into the body are excreted," he says. You can't find these strains in foods currently on the market, but not surprisingly, several companies are working to create a supplement that contains them.