Self-selected intake of carbohydrate, fat, and protein by obese (ob/ob) and lean mice

Obese mice, self-selecting from three food cups containing carbohydrate, fat and protein supplemented with minerals and vitamins, selected the same proportion of energy from protein (approximately 20%) as did lean mice. Young obese mice also selected the same proportion of carbohydrate and fat as selected by lean mice, but adult obese mice self-selected a higher proportion of energy from fat and a lower proportion from carbohydrate than did lean mice. The high preference by adult obese mice for fat was confirmed in additional studies employing two food cups, one containing a high-carbohydrate diet and the other a high-fat diet. We speculate that the preference by adult obese mice for fat is related to their insulin resistance.