Conjugated linoleic acid (CLA) is form of fat found in dairy foods, beef and other natural sources. When given to small animals, decreases of body fat have been noted.. Although weight loss is the best treatment for overweight and obesity, it is difficult to maintain the loss in the long term. Because of this, treatment emphasis has turned to small weight losses obtained through non-restrictive diets and prevention of weight regain. This is a study to determine if 6 months of consumption a purified form of CLA will result in greater loss of body fat than control and to determine whether CLA consumption increases total fat oxidation, which would help explain why the weight loss occurs.

Subjects were screened and then underwent baseline evaluation. The substudy evaluation measured 24-h energy expenditure and substrate utilization by using a whole-room indirect calorimeter. Dietary fat oxidation was measured by mixing [1-13C]oleate and D31-palmitate into a breakfast meal and then collecting breath carbon dioxide and urine to measure the end products of oxidation. Subjects were then provided either 4 g/d of 78% active CLA isomers (3.2 g/d: 39.2% cis-9,trans-11 and 38.5% trans-10,cis-12) or 4 g/d of safflower oil placebo as 1-g gel capsule supplements. The baseline evaluations were repeated 6 mo later.

Inclusion Criteria:

• BMI 25-29.9 kg/m2
• Absence of a weight change of greater than 3 kg in the previous 6 months

Exclusion Criteria:

• Presence of a physical limitation to walking exercise
• Current or recent (6 months) enrollment in a commercial or self-prescribed weight loss program
• A history of metabolic disease-ie. renal, endocrine, hepatic or gastrointestinal disease that would impact the outcome of the study
• A history of a psychiatric or eating disorders Ÿ Presence of metal implants that would interfere with body composition analysis
• Fasting plasma cholesterol >300mg/dl or triglycerides above 500 mg/dl.
• Abnormal EKG