Chromium is an essential nutrient involved in the regulation of carbohydrate and lipid metabolism. Normal dietary intake of chromium in humans and farm animals is often suboptimal. In addition to its effects on glucose, insulin, and lipid metabolism, chromium has been reported to increase lean body mass and decrease percentage body fat, which may lead to weight loss in humans. The effects of chromium on body composition are controversial but are supported by animal studies, which increase their validity. A subject's response to chromium depends on his or her chromium status, diet consumed, type and amount of supplemental chromium, and study duration. There have been no confirmed negative effects of chromium in nutritional studies. Chromium is only a small part of the puzzle in the control of weight loss and body composition, and its effects, if present, will be small compared with those of exercise and a well-balanced diet.