"The proportions of fat versus lean tissue in relation to overall weight is the critical measure."

Losing too much lean tissue increases the percentage of fat in your body.

On a more moderate diet, you lose 3 times more fat than lean tissue.

This should improve your muscle-to-fat body composition, resulting in more lean tissue and less fat.

Body water, the major component of lean tissue, diminishes.

What's more, the proportions of fat and lean tissue may change.

Exercise also helps maintain the body's level of lean tissue.

"Preserving lean tissue and losing body fat - that's what you need to strive for," Bryant says.

People lose lean tissue as well as fat when they shed pounds, the authors of the new study write.

In fact, they write, studies have found that lean tissue represents roughly a quarter of total weight loss.