Male C57BLA5J mice approximately 6 wk old were housed 5 mice/cage, and were assigned to one of five diets, provided ad ttbitum: Dl2451 (45kcal%fat, lard, Research Diets, Inc., New Brunswick NJ), D12450B (10kcal%fat, lard control), D12330 (58kcal%fat, hydrogenated coconut ouVHCO), D12328 (llkcal%fat, HCO control), and Teklad8604 (12kcal%fat, soy). The D12451 mice had increased mean body weight vs. the D12450B group as early as 1 wk after initiation of diet, but D12451 average body weight was similar to mice fed 8604 diet. Mice fed D12451 decreased g/d intake, and maintained kcal intake similar to D12450B, D12328 or 8604 diets for 9 wk (12-13 kcal/d). Mice on D12330 diet ate progressively more each wk for 9 wk on diet, at which time they were eating approx 27 kcal/d. The D12451 mice developed insulin resistance, 3 h fasting and fed hyperglycemia, glucose intolerance, hyperinsulinemia, hyperleptinemia after 5-7 wk on diet.