1. Eating a little less and exercising a little more, over the long term, won’t produce large, long-term weight changes. For a half century, experts have talked about the 3,500-kilocalorie (kilocalories are what we call “calories” in everyday speech). That means for every 3,500 calories you burn or don’t consume, you lose a pound. But this rule was derived from short-term studies. More recent data, the authors say, shows that people lose much less weight when they burn it over a longer period of time.