The idea that calorie restriction might extend the human lifespan goes back to the 1930’s, when lab workers first noticed that rats who didn’t get as much food as their brethren tended to live longer. Since then, similar studies have shown consistently that calorie restriction prolongs the life of certain organisms such as yeast, worms, flies, fish, and even mice. The increase is significant, in some cases up to 40%. So does it work in humans? We don’t know yet. Where this research got stuck was with rhesus monkeys.