In some recent articles, we’ve seen that vegetable oils cause obesity, heart disease, promote male infertility and aging, and are just generally bad news. In this article we’ll look at the evidence that vegetable oils cause insulin resistance.
In a study (full paper), mice were placed on a high-fat diet, with fat at 40% of calories, which is not terribly high for humans but is for mice. One group got their fat as corn oil, the other as olive oil.
The group on corn oil developed hyperinsulinemia (high blood insulin) and insulin resistance. See charts below.
The corn oil diet also spontaneously decreased locomotor activity, and by a great deal. See charts below.
Could increasing consumption of seed oils like corn oil be partly responsible for an increase in couch potato lifestyle? Maybe people who consume a lot of this stuff don’t feel like moving around much, and therefore increased seed oil consumption contributes to obesity by decreasing the amount of exercise.
Excess omega-6 consumption in mice is associated with negative metabolic and cardiovascular outcomes. Seed oils are loaded with omega-6 fatty acids.
That’s all very well for mice, but what about in humans? Does decreasing consumption of seed oils do anything for metabolism or obesity?
Turns out, it does.
A group of 93 men with non-alcoholic fatty liver disease, which is a consequence of obesity as well as sugar and seed oil consumption, were randomized to use either olive oil, canola oil, or soybean oil for cooking, at no more than 20 g a day. The study took place in India, where there’s a high consumption of seed oils in cooking – just like there is here in the U.S.
The olive oil group lost weight, and compared to canola oil, decreased insulin resistance and fasting blood sugar, and increased HDL. The canola oil group improved in some measures, but not as much as the olive oil group. (Canola is a “less bad” seed oil.) No changes were seen in the soybean oil group.
This study shows that a relatively small dietary change, using olive oil instead of soybean oil for cooking, can result in significant improvments in metabolism, and lends more evidence to the concept that seed (vegetable) oils cause obesity.
The American Heart Association recommends “heart-healthy” seed oils. Here’s their list of “healthy” oils:
The only one on that list that’s truly healthy is olive oil. The others will make you fat, diabetic, and give you heart disease.
Other establishment health organizations make the same claims.
Their advice is perverse. You’re much better off doing the opposite.
Their counsels have also fueled the obesity epidemic.
The evidence they’ve used for their recommendations is wrong. Re-analysis of studies that randomized people to polyunsaturated fats as are found in seed oils found that benefits occurred only when omega-3 fatty acids were more or less accidentally increased. When omega-6 alone was increased, death rates increased.
The evidence they’ve used is hopelessly biased.
Vegetable oils are better termed industrial seed oils both for their source, which is not vegetables but seeds, and for their mode of production, an industrial process that uses high heat and organic, gasoline-like solvents.
If you want to preserve or attain good health, don’t use them.
If you need fat for cooking, use butter, ghee, lard, tallow, or coconut oil. For cold uses, olive oil.