Body fat serves as a crucial energy reserve, influencing eating behavior through the brain's regulation mechanisms. Leptin, a hormone discovered in the 1990s, plays a key role in signaling the body's fat levels, guiding our urgency for food intake. The fascinating history of mutant mice from the 1950s sheds light on the genetic underpinnings of obesity, revealing how different strains exhibited similar hyperphagic traits despite mutations on various chromosomes.