Exercising more won't necessarily help you lose more.
Everything in moderation—including exercise, it turns out. Sedentary men who worked out daily for 30 minutes lost more weight over 13 weeks than those who worked out at the same intensity for an hour, found Danish researchers last year (an average of 7 pounds vs. 5 pounds). The study authors believe that the shorter exercise sessions inspired the men to get up and get moving, while also allowing them "to burn calories without wanting to replace them so much," they told the New York Times. The longer exercise sessions seemed to be more tiring and left the men without enough surplus energy to, say, take the stairs, and their food diaries also showed that they were eating more than usual. (That said, both groups of exercisers lost more weight than members in the control group, who engaged in no extra activity at all.)