Inhibitor of DNA binding 2 (ID2) is a helix-loop-helix transcriptional repressor rhythmically expressed in many adult tissues. Our previous studies have demonstrated that Id2 null mice have altered expression of circadian genes involved in lipid metabolism, altered circadian feeding behavior, and sex-specific enhancement of insulin sensitivity and elevated glucose uptake in skeletal muscle and brown adipose tissue. Here we further characterized the Id2-/- mouse metabolic phenotype in a sex-specific context and under low and high fat diets, and examined metabolic and endocrine parameters associated with lipid and glucose metabolism. Under the low-fat diet Id2-/- mice showed decreased weight gain, reduced gonadal fat mass, and a lower survival rate. Under the high-fat diet, body weight and gonadal fat gain of Id2-/- male mice was comparable to control mice and survival rate improved markedly. Furthermore, the high-fat diet treated Id2-/- male mice lost the enhanced glucose tolerance feature observed in the other Id2-/- groups, and there was a sex-specific difference in white adipose tissue storage of Id2-/- mice. Additionally, a distinct pattern of hepatic lipid accumulation was observed in Id2-/- males: low lipids on the low-fat diet and steatosis on the high-fat diet. In summary, these data provides valuable insights into the impact of Id2 deficiency on metabolic homeostasis of mice in a sex-specific manner. (C) 2014 Elsevier Inc. All rights reserved.