Vegetable Oils Cause Insulin Resistance

Factory producing vegetable oil

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.

Corn oil causes insulin resistance in mice

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.

Decreasing seed oil consumption in humans

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 health establishment recommends seed oils

The American Heart Association recommends “heart-healthy” seed oils. Here’s their list of “healthy” oils:

  • Canola
  • Corn
  • Olive
  • Peanut
  • Safflower
  • Soybean
  • Sunflower

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.

PS: For more on how to live longer, see my book Stop the Clock.

PPS: Check out my Supplements Buying Guide for Men.

Share this post with your friends

Want to permanently lose 20-50 pounds in 12 weeks?

Without going hungry, counting calories or doing cardio


  1. Dave says:

    Mr. Mangan, what are your thoughts on avocado oil? Avocado oil and avocado mayonnaise are now available, and the oil is marketed as having a high “smoke point” which, as I understand it, is supposed to be good for cooking at high heat.

  2. Drifter says:

    Just for the record in case any of the assembled braintrust here ever gets into a discussion with someone under the influence of mainstream health thinking, there has been a study being cited to defend seed oils which compared seed oils to saturated fat for their affect on insulin resistance and the seeds oils appeared to be the slight winner. The problem as far as I know however, is that it was a very short-term study (7-10 days I think), and as Ron Rosedale in particular has stressed, dietary saturated fat can in fact impair insulin sensitivity until one is adapted to it, which for a sugar-burner adapting to fat intake, takes somewhere between 2-6 weeks. This is why he recommends that people switching form a high-carb to a high-fat diet go easy on the saturated fat for the first 6 weeks or so.
    Also, some people cite short -term FMD studies to suggest that olive oil is a problem, however again, this has been shown (e.g. by Volek) to not be an issue after a period of adaptation.

    • P. D. Mangan says:

      Thanks, Drifter. “Assembled braintrust” – I love it. I’m not aware of either of the studies you mention, so if you come across them, that would be good to know.

  3. Nikita says:

    Is sesame oil and/or mustard oil considered vegetable oil?

  4. Rob says:

    All you need to know about the industrial seed oils is how they are made (there are videos online that show the process). Basically, it involves a harsh extraction process that includes bleaching, deodorizing and the use of the highly toxic solvent hexane. Does that sound like something humans were meant to consume? No thanks…………

  5. Jenn says:

    Great article!
    What are your thoughts on walnut oil and pecan oil? I use walnut oil in salad dressings and pecan oil for certain types of high heat cooking (I also use coconut, bacon fat , olive and avocado oils). Are these two oils healthy in your opinion?

    • P. D. Mangan says:

      Thanks. Jenn. Walnut oil is over 50% polyunsaturated fat, most of it o-6. I personally wouldn’t use it. I can’t find any data on pecan oil.

  6. bigmyc says:

    I have scoped the two recent posts regarding industrial seed oils and the preponderance of insulin resistance, but I must have missed any of the explanations as to the mechanism by which such derangement occurs. Is it basically do to the mitrochondrial dysfunction of the excessive O-6’s that cause the deregulation of glucose? What else might be at work here?

  7. Ted Maynard says:

    According to Dr. Paul Saladino, vegetable oils cause IR adipose tissue by making them insulin SENSITIVE, which causes them to get too big, causing release of fatty acids which make the rest of your body insulin resistant. He states that to be healthy you WANT IR in belly adipose tissue as this makes your other cells not IR. This is counter to what I have understood, but it is interesting. Here is an article that includes this; in addition to what is written, Dr. Saladino discusses this near the end of the video that you will find in this article. See

Leave a Reply

Your email address will not be published.