This summer, 25 overweight and obese adults participating in a tightly controlled feeding study will take up full-time residence for 3 months at a wooded lakefront center in Ashland, Massachusetts. However, before checking in at Framingham State University’s Warren Conference Center and Inn, they will have to lose 15% of their body weight on a calorie-restricted diet with home-delivered meals.

Those who pass this hurdle will be invited to the inn, where they’ll be randomly assigned to 1 of 3 equal-calorie diets: a low-fat, high-carbohydrate diet that’s either high or low in added sugar or a very low-carbohydrate, high-fat ketogenic diet that causes the body to switch from burning carbohydrates to burning fat.