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.
Natural selection means that the organisms better adapted to their environment, that is, they have developed the right characteristics/skills/response to the external ambient, have higher chance to survive, making the next generations genetically inherit such acquired surviving characteristics.
These generations will thus have a higher chance of survival, making these species being "naturally selected" as survivors, while those who haven't or are slower in this process, have a higher risk of elimination.
