Aside from maybe noted bald guy Dwayne "The Rock" Johnson, most guys value a thick head of hair (especially if you're starting to thin out on top at an alarming rate). Likewise, most dudes want wrinkle-free, smooth, young-looking skin.
Having a lower overall weight and less fat around your body to keep you warm may spur your body to grow more hair and increase blood flow to the skin—thereby resulting in more hair and better skin, says a recent study published in Cell Reports.
In a six-month study, researchers compared two groups of mice: one given as much food as it wanted, another restricted to 60% of the calories eaten by the gorgers. After half a year, the deprived rodents ended up with thicker, fuller, and longer fur. Researchers also saw three times more blood vessels in the skin of the food-restricted mice, which increased blood flow and kept it looking younger.
"Fur has properties that insulate animals to retain warmth," said Alicia Kowaltowski, Ph.D., a professor at the University of Sao Paulo’s Institute of Chemistry in Brazil. "We believe this is an adaptation present in mammals. Those that eat less have less fat, and they need more fur or body hair as thermal insulation [and] the change in vasoconstriction helped the slimmer mice stay warm, and their skin also remained young.”
Of course, the study wasn't done on humans—so it's hard to say exactly how well the same logic applies to humans. But we're all for one more reason to motivate people to become leaner, younger-looking versions of themselves.