American College of Sports Medicine looks at keto diets

A group of people following a ketogenic diet (10% carbs, high fat) were asked to maintain their normal activity level and to eat sufficient calories equal to maintenance. At the end of the study, subjects lost 2.8 kilograms of bodyweight (6.6 lbs), and 4% of bodyfat (peformed by DEXA analysis). Additionally, they gained 1.4 kilograms of lean mass (3.08 lbs).

(Med Sci Sport Exercise , 33(5): S336, 2001)