Human Predation Cues Prevent Obesity
The thrifty gene hypothesis proposes that genes that allow humans to efficiently process food into fat deposits increases survival and reproductive fitness during periods of food shortage and reduces the risk of death from infectious and chronic disease. Although these genes were historically advantageous, these genes now contribute to obesity in wealthy nations, preparing us for famine that never comes. However, predation of early humans may have also provided us with genes to reduce fat deposition when human predators are present as carrying around a large fat store reduces speed and increases the probability of being killed by a predator.
Controlled rodent studies demonstrate that exposing rats to predator odor decreases body weight without reducing food intake. Placing predator scent in close proximity to food sources further decreases prey species body weight by reducing food intake. This data suggests that genes preventing obesity are activated in the presence of predators to increase speed reducing the risk of being killed. Many early human fossils show signs of predation mostly from large predatory cats. Although human predation has decreased with the invention of weapons and fire, the evolutionary legacy of human predation by large cats may have provided us with similar obesity preventing acclimation responses to predation.
Activation of these obesity preventing responses in modern human populations is low as many of the large predatory cats that humans evolved with are extinct and most humans do not live in close proximity to lions, tigers, and bears. Tiger urine can be obtained from Chinese medical practitioners and as an animal repellent from western sources. Tiger urine may reduce body weight and food intake when applied near eating areas, but the musky odor and high price prevent large cat urine from becoming a universally adopted weight loss aid.
Most attribute the health benefits of domestic cat ownership to reduced stress, but these health benefits may also derive from the activation of human predation responses. Many cat owners spay or neuter their cats decreasing potentially beneficial urine spraying behavior, but placing cat litter boxes near human eating areas should also reduce human fat deposition and food intake.