Rudy Has Been on a Strict Diet of 1000 Calories

Rudy has been on a strict diet of 1000 calories per day for the last six weeks.He lost considerably more weight in the first three weeks of his diet than in the last three because

A) his basal metabolic rate has decreased.
B) his set point has increased.
C) lean tissue is maintained by fewer calories than is fat tissue.
D) his fat cells have begun to secrete elevated levels of leptin.