[Editor's Note: Social networking sites work well for weight loss companies.] Todd Wasserman - Mashable - 12/29/10 Everyone knows the secret to weight loss is diet and exercise, but increasingly there’s another component as well: social media.

As the big weight-loss firms gear up for New Year’s, typically their busiest time of year, some are emphasizing the size and scope of their online support networks. For other marketers, the homegrown social networks for Nutrisystem and Weight Watchers will no doubt spur envy: The former claims about 3 million people while Weight Watchers has 2.3 million. Both networks are only about three years old, and both brands have thriving communities on Facebook as well. Read the full story.