One of the most powerful resources you have for helping you lose weight—and keep it off—is your social network. Find a buddy who is also trying to lose weight and agree to help each other stay motivated. One study found that when friends participated in a group weight-loss program together, they lost more weight—and were more successful in keeping it off—than people who did the same program on their own. And a 2011 study found that when co-workers were put into two groups and competed together for the biggest weight loss, they dropped more weight than people who followed a worksite weight-loss program alone.