Simple Science: How Excess Insulin Makes Us Fat


“…obesity is impossible in the absence of adequate tissue concentrations of insulin.” – M. Goldberg, in Journal of the American Medical Association

In the last post we touched on how hormones control the metabolic conversation that determines if we are storing or burning body fat. Let’s now dig into the hormone insulin’s role in this conversation as it is known in scientific circles as, “The most important hormonal factor influencing lipogenesis [body fat creation].”

Insulin’s job is to get energy into cells. For example, after we eat lunch, our body digests it and then releases insulin to carry those freshly digested calories into our cells. Since insulin is activated only when we need to get fuel into our cells, our metabolism “hears” insulin in the bloodstream “communicating” that we have energy on its way to our cells and therefore do not need to use any stored energy—aka burn body fat. So the hormone insulin—not the calories we ate—blocks the burning of body fat. That point is extremely important.

“[Insulin signals an] abundance of [external] energy, [and]…fat breakdown is suppressed and its synthesis promoted…” – researcher G. Wilcox, Mepoundourne Pathology

Our metabolism does not decide to burn or store body fat based on calories. It makes these decisions based on the hormones those calories trigger. That is why the quality of calories matters so much. As we have already seen, higher-quality calories trigger body-fat-burning hormones while low-quality calories trigger body-fat-storing hormones.

“Fat is mobilized [burned] when insulin secretion diminishes.” – The American Medical Association

We can cut calories all day and will not burn body fat effectively if we are eating low-quality calories which trigger excess body-fat-storing hormones such as insulin. Why? Hormones like insulin remove our ability to burn body fat regardless of whether or not we need to according to calorie quantity. That is why scientists refer to the hormone insulin as the “principal regulator of fat metabolism.”

Here is the sad part. Calories from inSANE starch and sweets trigger the release of ridiculous amounts of insulin. All that insulin gets those inSANE starch and sweets’ calories into our cells, but then we still have insulin left over in our bloodstream. That excess insulin clogs us up and removes our ability to burn body fat.

Where the Average American Gets Calories

(Insulin-spiking starch and sweeteners make up 43% of what we eat)

“…obesity [is characterized by] defects in insulin action, whole-body insulin resistance, and hyperinsulinemia” – researcher D.A. York, Pennington Biomedical Research Center

Things go from bad to worse if this inSANEity keeps up for too long. Not only does all the excess insulin destroy our ability to burn body fat, it makes the metabolism resistant to insulin. How does this process work? Compare becoming resistant to the effects of insulin with becoming resistant to the effects of alcohol. When people drink alcohol in moderation, everything is fine. It takes relatively little alcohol to generate the desired effect, so people don’t drink too much of it. However, if people drink too much alcohol, they become resistant to alcohol’s effects. Then they have to drink more alcohol to get the desired effect. This volume of alcohol eventually destroys their liver and makes them gain body fat. This leaves heavy drinkers in an unfortunate place where they have become resistant to alcohol and have to drink an unhealthy amount of it to get the desired effect.

Similarly, when people eat mostly SANE foods and just a little inSANE starch and sweets, everything is fine. It takes little insulin to get energy into cells, so the body doesn’t produce too much of it. However, if people eat mostly starch and sweets, their bodies become resistant to insulin’s effects. Then their body has to produce more insulin to get energy into cells. This volume of insulin eventually destroys their pancreas and makes them gain body fat.

“Foods made from wheat flour account for about 20% of the calories in the American diet…” –Marion Nestle, New York University

Even more unfortunate, at least one in four Americans are insulin resistant. All this excess insulin forms the backbone of the hormonal dysfunction causing us to gain fat. Not only does it crush our ability to burn body fat, it also increases the rate at which we store body fat because excess insulin preferentially puts calories into our fat tissue. This happens because no matter how resistant other tissues become to insulin, our fat tissue is always receptive. And while that is technically good because it keeps insulin resistance from killing us, it can crush any dreams of losing weight. We end up with more body fat and no ability to burn it. This sad state is know as internal starvation and will be the subject of the next post.

Jonathan Bailor!/jonathanbailor
(212) 465-3130

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9 replies
  1. Rebecca Tonn
    Rebecca Tonn says:

    Fantastic article, Jonathan. Thank you for explaining the role of insulin. I switched to a Primal/Paleo, very low-carb way of living in January. Wish I’d known this decades ago!

  2. Jina
    Jina says:

    Hi, I agree with the science and that we must not consume such large amounts of starches and sugars, but my concern is that in your recipes you include artificial sugars such as splenda. Others such as mark sisson do not agree with this substance. This concerns me as your research is so relevant to your work. What is the science behind this substance that is so concerning with other paleo sites. Looking forward to your reply as this is what is holding me back from buying your book.

    • Jonathan
      Jonathan says:

      Hi Jina – Thank you and you are right that ideally we would not consume these substances. The point The Smarter Science of Slim makes is that if one is unwilling to go the rest of their lives without sweeteners, my research shows that non-caloric natural sweeteners such as stevia are much less detrimental than caloric sweeteners such as sugar or high-fructose corn syrup.

      Super SANE= No sweeteners of any kind
      SANE = Non-caloric sweeteners
      inSANE = Caloric sweeteners

      Great question and hope this helps.

      – Jonathan Bailor

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