#1: Paleo Diet
This plan recommends you eat like your caveman ancestors, emphasizing lots of fruits, veggies, lean meats and seafood. Dairy and grains aren’t allowed on the plan—omitting two important food groups and numerous important nutrients in your diet. This diet was ranked last by US News and World Report on their list of Best Weight Loss Diets. Their expert panel determined that there is a lack of scientific evidence to show that long-term weight loss can be achieved.
#2: Dukan Diet
Although celebs like Gisele Bundchen and Jennifer Lopez have reportedly followed this diet post-baby to shed pounds, it was ranked second to last by US News and World Report’s Best Weight Loss Diets. This updated version of the Atkins diet eliminated carbs, fruits and veggies (especially during the very strict first phase), while allowing unlimited amounts of lean protein. It’s a very restrictive plan that will have you losing weight rather quickly—actually too quickly according to safety guidelines set up by the National Institutes of Health. The end result: You’ll probably end up regaining your lost weight plus more.