1. People on western diets. This isn't some hidden mystery.. it's in plain view. Plenty of studies done, or just ask _any_ doctor that sees patients, or any of your friends/family who have tried diets. Or search pubmed for diet adherence.
2. Because their base metabolic rate reduces over time to match their new reduced caloric intake.
2. Because their base metabolic rate reduces over time to match their new reduced caloric intake.