The Keto diet was very popular in 2018, but experts say this rich in fat diet isn't great for you. It did, however make the number two spot on the list for the fastest weight loss diet.
WW (formerly known as Weight Watchers) landed a number 1 spot on the list since it doesn't restrict any one food, you just learn to eat in moderation based on their point system.
See all 41 diets and where they rank!