If I would have to make a good guess, I would choose A.
Thrifty metabolism
Thrifty metabolism is the genetic
tendency toward efficient use of energy that results in below-average energy
requirements and increased storage of calories as fat. Thrifty metabolism
contributes to less weight lost when an obese person reduce the amount of his
calorie intake even though there is changes in metabolism.
Only unicellular orgaimns I might be wrong
