Conjugated linoleic acid (CLA) is really two supplements - chemical mirror images with opposite benefits. As sold in stores, CLA is a mixture of two isomers: 9,11 and 10,12. The 10,12 variety reduces gains of fat quite reliably in rat and pig studies. Human studies have not been so conclusive, but a fat-loss effect was nonetheless demonstrated in overweight and middle aged specimens.
9,11 CLA may increase muscle mass and/or strength. Large doses in novice bodybuilders appeared to boost gains in muscle size and strength over six weeks.
Because available CLA brands have both the muscle and strength-building 9,11 isomer and fat-reducing 10,12 isomer, you get the best of both worlds - more muscle and less fat - which means it's a good supplement for any phase of training.
Dosage: 5.6-7.2 grams per day of CLA may be needed for gains in muscle mass or strength. For fat loss, 3.4 grams per day is the lowest dose that has met with success in human fat-loss trials.