Can real people on real diets "keep the lean, lose the fat?"

No, says Dr. Gilbert Forbes of the University of Rochester's Medical Center."Whenever people lose significant amounts of body weight, they lose some lean tissue in addition to the fat," he says. "Conversely, when people gain weight, most is in the form of fat, but a small proportion is lean tissue. Most obese people have not only larger stores of fat, but larger hearts, livers, kidneys, spleens and pancreases. Their skeletons are heavier, too. Probably the larger organs and heavier frame help support the extra weight."