There's some truth that having sex burns calories, but it's not as much as some people claim. There are rumors you can burn several hundred calories while having sex, but researchers say you're really only able to burn a few calories each minute. That's about the same as taking a leisurely walk.
Among the other myths or assumptions the authors cite, based on their review of the most rigorous studies on each topic are:
- Small changes in diet or exercise lead to large, long-term weight changes. Fact: The body adapts to changes, so small steps to cut calories don't have the same effect over time, studies suggest. 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.
- School gym classes have a big impact on kids' weight. Fact: Classes typically are not long, often or intense enough to make much difference.
- Losing a lot of weight quickly is worse than losing a little slowly over the long term. Fact: Although many dieters regain weight, those who lose a lot to start with often end up at a lower weight than people who drop more modest amounts.
- Snacking leads to weight gain. Fact: No high quality studies support that, the authors say.
- Regularly eating breakfast helps prevent obesity. Fact: Two studies found no effect on weight and one suggested that the effect depended on whether people were used to skipping breakfast or not.
- Setting overly ambitious goals leads to frustration and less weight loss. Fact: Some studies suggest people do better with high goals.
The Associated Press contributed to this report.