"Fat is stored in the layer right beneath the skin, called the adipocite," said George Lesmes, our featured mentor on those fat cells which we don't know all that well despite repeated efforts to study them in the bathroom mirror. Lesmes is the director of the Center for Exercise Science and Cardiovascular Research at Northeastern Illinois University. He studies fat. He understands fat. More importantly, he is a scientist who discusses fat in simple terms.

"When we move our muscles, the fat layer is activated and dumped into the bloodstream," he explained. "Blood takes the fat to the muscles being used. Inside the muscle, the fat is broken down into molecules in a process we call aerobic metabolism. The molecules are released and provide the energy for muscles to contract."

Lesmes calls this steady-state aerobic exercise, and mentions walking, running and cross-country skiing (including indoor ski trainers) as prime examples. According to a number of exercise research studies, other top fat burners are rowing, stair climbing, jumping rope, boxing, squash/racquetball and aerobic dancing. Bicycling makes the cut if you go long enough; 40 minutes on the bike is equal to about 20 minutes of jogging. (Don't forget that 40 minutes on the bike brings other benefits to the heart, lungs and blood.) Water aerobics, though less widely studied, also draw praise for their anti-fat potential.