Tip of the day: Watch portions, lower your BMI

We recently asked always-thin people to tell us how they stay that way, and of all the eating behaviors we asked about, carefully controlling portion size at each meal correlated most strongly with having a lower BMI. And the successful losers we spoke with—even those who were still overweight—were especially likely (62 percent) to report practicing portion control at least five days per week. So did 57 percent of the always thin, but only 42 percent of failed dieters.

Read our stay-thin strategies, and get advice on how to increase your chances of weight-loss success.