Sex to burn calories? Authors expose obesity myths Associated Press Copyright 2013 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Published 4:00 pm, Wednesday, January 30, 2013 School gym classes make a big difference in kids' weight. "The evidence is what matters," and many feel-good ideas repeated by well-meaning health experts just don't have it, said the lead author, David Allison, a biostatistician at the University of Alabama at Birmingham. [...] many of the report's authors also have deep financial ties to food, beverage and weight-loss product makers — the disclosures take up half a page of fine print in the journal. "The big issues in weight loss are how you change the food environment in order for people to make healthy choices," such as limits on soda sizes and marketing junk food to children, she said. Yet the only study that scientifically measured the energy output found that sex lasted six minutes on average — "disappointing, isn't it?" — and burned a mere 21 calories, about as much as walking, he said. Among the other myths or assumptions the authors cite, based on their review of the most rigorous studies on each topic: At least one outside expert agrees with the authors that the "small changes" concept is based on an "oversimplified" 3,500-calorie rule, that adding or cutting that many calories alters weight by one pound. —Setting overly ambitious goals leads to frustration and less weight loss.