You’re walking down a city street and you hear a voice calling to you. It says, “Psssst. Hey buddy. Are you looking to score? I’ve got what you’re looking for. How about a KFC fried chicken breast? Or this salad, covered with our tasty vegetable oil dressing? Go ahead…try it. The first one’s free.” OK, other than on advertisements in the windows of fast-food restaurants, most of us don’t really often hear the voices of drug pushers as we’re walking down the street. But our brains hear them, calling to us and urging us to score some acid – linoleic acid.
That’s the constituent of corn oil, cottonseed oil, soybean oil and other polyunsaturated vegetable oils that triggers our brains into creating its own version of marijuana or cannabis. Called endocannabinoids, these naturally occurring psychoactive compounds play an important role in controlling what we perceive as our appetite. The more of these endocannabinoids our brains produce, the hungrier we get, and the more we tend to want to eat, or overeat.
Interestingly enough, recent research by Joseph Hibbeln, a neuroscientist at the National Institutes of Health, indicates that this is exactly what our high-in-fat, high-in-vegetable-oils diets are doing to us. As he puts it, “You’re chronically a little bit stoned.”
Allostasis, and how it controls what we eat, and when
One of the most important functions that our brains perform is to monitor the number of calories we ingest in the form of food and compare that with our expenditures of energy. To stay healthy, or to maintain a constant weight, a human needs to take in approximately the same number of calories that he expends. Whereas in the past scientists believed that this process was controlled on the basis of trial and error, now they tend to agree that it is more of a predictive behavior, one based more on the brain’s internal signals than on external events. The brain anticipates how much we need to eat, based on its own inner chemistry, and then produces hormones that send signals to our body telling it how much to eat. This process is called allostasis. If the brain is constantly a little stoned on endocannabinoids, allostasis is going to tell the body to eat more.
In an upcoming issue of the journal Obesity, Hibbeln and his associates make the case that diets high in vegetable oils mess with allostasis. High quantities of linoleic acid in these oils trick the brain into producing more endocannabinoids, and they in turn trick the body into thinking it is in danger of starving, when it really isn’t.
In animal studies, Hibbeln fed some of them a diet that mimicked the typical American diet circa 1900, with only 1% of its calories coming from the linoleic acid in vegetable oils. They fed another group of the animals a diet more in line with today’s All-American diet, in which 8% of its calories came from linoleic acid/vegetable oils. Both groups got exactly the same proportion of fats and carbohydrates from their caloric intake, but the animals who consumed more linoleic acid gained much more weight. Furthermore, they tended to gain and store more of that weight as fat.
What does this mean for us humans?
Well, put simply, if we’d like to be able to eat more and yet gain less weight, and less of it as stored fat, we need to revert to a 1900s-era diet, in which we’re ingesting fewer vegetable oils. These oils, and the linoleic acid they contain, are in the researchers’ opinion keeping us stoned, and keeping us fat. We’ve perpetually got the munchies.
When consumption of various vegetable oils by Americans are charted over time, we see that the number of kilograms per person per year have not gone up all that much between 1900 and now. But the number of kilograms/person/year of linoleic acid have risen from less than 1 kilo to over 12 kilograms per person per year. Part of the reason for this is a shift to the use of more soybean oil, which contains high percentages of linoleic acid.
The researchers suggest that those who want to lose weight or maintain their current healthy weights consider shifting to the use of oils that contain lower percentages of linoleic acid, such as olive oil, sunflower oil, or high-oleic canola oil. Adding Omega-3 fatty acids to ones’ diet in the form of fish oil can also help, because in Hibbeln’s experiments mice who were getting a diet high in linoleic acid became more resistant to weight gain if they were also receiving fish oil.
All of this research is preliminary, of course, and so far has only been conducted in animal studies. But since the benefits of a “Mediterranean diet” stressing olive oil and other oils low in saturated fats have been strongly established, as have the benefits of taking fish oil supplements, Hibbeln’s advice makes sense. In a way, it’s using one set of oils (olive oil and fish oil) to offset and counteract the effects of another set (vegetable oils). As the hippies used to say, “Better living through chemistry.”