Obesity is increasing in prevalence worldwide and has serious consequences for healthcare providers, but the molecular mechanisms involved in fat accumulation remain poorly understood. In October Nature Medicine, Kyoko Tsukiyama-Kohara and colleagues at McGill University, Montreal, Canada, show that the protein 4E-BP1 can enable white fat (a reserve of energy) to adopt the properties of brown fat (a source of heat generation) and can increase energy expenditure (Nat Med 2001, 7:1128-1131).

The protein 4E-BP1 is an inhibitor of mRNA translation and is highly phosphorylated in the adipose tissue in response to insulin treatments. Tsukiyama-Kohara et al. investigated the biological function of 4E-BP1 by disrupting its gene (Eif4ebp1) in the mouse. They found that Eif4ebp1^–/– mice had smaller white fat pads than wild-type animals, and an increased metabolic rate. The white fat present in these mice had taken on the properties normally associated with brown...