A new review of 18 previous studies found that CLA or conjugated linoleic acid, a fatty acid found in beef, lamb and dairy products seems to promote body fat loss.

Dr. Leah D. Whigham, of the University of Wisconsin at Madison and colleagues found that people who took CLA lost an extra 0.2 pounds of fat each week compared to those who took a placebo.

The researchers suggest that CLA may interfere with the body metabolism and make it hard for the body to store fat.

However, to experience the effect, one needs to take 3.2 grams per day, which is hard to get through any diet.   One liter of full fat milk can only provide 1 gram of CLA.

In addition, CLA has been found to have a number of side effects including promoting insulin resistance.

The study was published in the May issue of American Journal of Clinical Nutrition.