I've heard great things about the eDiets affiliate program.
Here is info from their affiliate page
"eDiets.com is the Internet's premier diet and healthy living destination, offering over 20 different popular diet plans that affiliates can introduce their visitors to. From the Mediterranean Diet to the Mayo Clinic Plan, anyone can tap into a recipe for weight loss success at eDiets. As an affiliate, you'll earn up to a $30 CPA commission for every diet plan purchase you refer, and you'll be promoting a trusted name that has revolutionized health and fitness on the web."
They are managed by ShareResults, one of the best networks I work with.
Here is all the info:
http://www.shareresults.com/local_affiliate_desc.php?mid=2265
Hope this helps and best of luck!