New Horizons in Science

See if this sounds familiar: You eat pretty well Monday through Thursday. Then you celebrate the weekend with a burger, fries, and a beer Friday night. And Saturday or Sunday, you nibble on junk while watching a ball game or a movie. On Monday, you want to get back on track, but you’re hungrier than you were on Friday. Deborah Clegg has an explanation: Fat in your brain is making your cells more resistant to the hormones that regulate weight, such as insulin and leptin. The brain, composed partly of fatty acids, actually incorporates the fat you eat into its structure, whether that fat is healthy olive oil, or the saturated fat in a Twinkie. Clegg has also discovered dramatic differences between fat cells in men and women, perhaps explaining why men gain in their bellies and women on their hips and thighs. She’s also found that estrogen plays a critical role in the process.