Your brain may see weight loss as a threatResearchers say the brain evolved during periods when food was unpredictable, and starvation posed a constant risk. As a result, the body developed sophisticated systems to protect stored fat, treating weight loss as a potential survival emergency. When body weight drops, hormones that stimulate hunger increase while the body simultaneously reduces the number of calories it burns. Their recent work also suggests the brain can establish a previously higher body weight as its new "normal." Experts also emphasize that better health does not always require dramatic weight loss.