Two scientists from the National Institutes of Health (NIH) have presented a new mathematical model to calculate reductions in caloric intake needed to lose weight. The old formula of a reduction of 500 calories/day resulting in a pound a week weight loss is wrong, according the researchers. The reason for the error is that, as weight is lost, metabolism slows down. Therefore, ever greater intake reductions are needed. This is why so many dieters feel like failures. Bottom line: It’s not their fault. The researchers presented at AAAS in Vancouver. Battling obesity with better mathematical models They have an on-line tool (which is not that easy to use) http://bwsimulator.niddk.nih.gov/favicon.ico . Their work was published in Lancet. Quantification of the effect of energy imbalance on bodyweight : The Lancet.