Stoned On Fat?

Neuroscience researchers at UC Irvine, , led by Daniel Piomelli, have just announced results of a study done on rats, in which they found that ingestion of fatty foods stimulates the release of endocannibinoids, chemicals that activate the same receptors affected by THC.  According to the UC Irvine news release:

"The process starts on the tongue, where fats in food generate a signal that travels first to the brain and then through a nerve bundle called the vagus to the intestines. There, the signal stimulates the production of endocannabinoids, which initiates a surge in cell signaling that prompts the wanton intake of fatty foods, Piomelli said, probably by initiating the release of digestive chemicals linked to hunger and satiety that compel us to eat more."

In other words, rats eating fats had the munchies.  Feeding rats carbohydrate or protein did not have this effect.  Piomelli offers an evolutionary explanation:

"Piomelli said that from an evolutionary standpoint, there’s a compelling need for animals to consume fats, which are scarce in nature but crucial for proper cell functioning. In contemporary human society, however, fats are readily available, and the innate drive to eat fatty foods leads to obesity, diabetes and cancer."

The study results will appear this week in the online edition of Proceedings of the National Academy of Sciences. 

This finding dovetails with the reward theory of overeating, suggesting that animals including humans get more immediate endogenous drug-like reward from eating fats than carbohydrates or proteins, partially because fats supply more than twice as much energy per gram as carbohydrate or protein.

Piomelli apparently also serves as Director of the UCI School of Medicine’s Center for Drug Discovery & Development and hopes to find a pharmaceutical solution:

"The findings suggest it might be possible to curb this tendency by obstructing endocannabinoid activity – for example, by using drugs that “clog” cannabinoid receptors. Since these drugs wouldn’t need to enter the brain, they shouldn’t cause the central side effects — anxiety and depression — seen when endocannabinoid signaling is blocked in the brain, Piomelli noted."

So there you go, a pharmaceutical solution to the obesity problem.   Just throw a monkey wrench into the intricate and poorly understood symphony of neurochemicals.  No need to worry about side-effects, right?

How about teaching people to recreate the ancestral environment instead?  What did he say?  "Fats are scarce in nature."  By "nature" he means in the ancestral environment. 

Could this be why humans need only about 20-25 g of essential fats daily, compared to ~50-60 g of protein and at least 150 g of glucose?  Does it make sense that human macronutrient requirements would mirror the relative availability of nutrients in the ancestral environment and diet?

And are things really that different in the agricultural food supply?  I mean, although fat seems abundant in industrialized nations, does this reflect nature, or human intervention?  After all, agriculture is part of nature.  Does agriculture produce more fats, proteins, or carbohydrates?  If you look at the world at large, at the entire human food supply on the planet, is fat relatively abundant, or relatively scarce, although concentrated in certain locations?  How about protein?  Carbohydrate?

Why would evolution favor a system that offers an animal a higher immediate reward for eating fats than for eating protein or carbohydrate? 

Would this reward system be more advantageous in an environment where fats were easy to obtain, or in an environment where fats were hard to obtain?

In other words, would nature make it more highly rewarding to eat something available frequently, with little effort, or something available only infrequently and with great effort?

From another angle, which would this system help most:  an animal that had a continuous supply of fats, or one that had an intermittent supply of fats?