Insulin Sensitivity Is Critical for Health

Evolution from ape to obese man

Insulin is the hormone that promotes uptake of nutrients into cells; it rises after eating, especially with consumption of carbohydrates and protein, and the amount of insulin required for this task varies depending on the individual’s insulin sensitivity.

Insulin sensitivity is critical for health.

Insulin binds to receptors on cell membranes, and when only minimal amounts of insulin are required for the task of facilitating nutrient uptake and controlling blood sugar (glucose), an individual is said to be insulin sensitive. When greater amounts of insulin are needed, this is insulin resistance; when even a high amount of insulin can’t control blood sugar, an individual has type 2 diabetes.

Type 2 diabetes is associated with greatly increased risks of coronary heart disease, kidney disease, Alzheimer’s, infections, and cancer. Most people are at least vaguely aware of this, but the most important point for this discussion is that insulin resistance occurs on a continuum, and most people have some degree of it.

How important is insulin sensitivity and its converse, insulin resistance?

Check out the chart below, which I discussed here.

In the lowest tertile of insulin resistance, no one got sick.

A group of 208 “apparently healthy”, non-obese volunteers (98 men, 110 women), had their level of insulin resistance determined. The subjects were divided into tertiles (thirds) of insulin resistance, low, medium, and high.

Doctors then followed the subjects for an average of 6.3 years each and looked for the “clinical endpoints” of hypertension, coronary heart disease, stroke, type 2 diabetes, or cancer. They found a total of 40 clinical endpoints in 37 of the subjects.

All of the disease was found in subjects with some degree of insulin resistance. Those with little to no insulin resistance had zero clinical endpoints, those in the middle had some disease, and those with the highest insulin resistance (lowest insulin sensitivity) had the greatest number of clinically significant diseases.

Keep in mind that these people were “apparently healthy”, non-obese, and that the researchers merely divided them into 3 equally sized groups.

Up to 80% of people with a normal glucose tolerance test, i.e. they are not diabetic, have some degree of insulin resistance. These people are at high risk for the diseases of aging and of civilization: heart disease, cancer, and the rest.

Insulin resistance is like an iceberg in which most of the risk is submerged and out of sight.

The fasting insulin test is a reasonable proxy for insulin resistance; all things equal, the lower the better.

The Kitavans, the South Pacific people who are well-known for the complete absence of cardiovascular disease, have much lower fasting insulin than comparable people in Sweden, and it does not increase with age.

American adolescents have much higher insulin levels, about 3 times as high as Kitavans, and it’s much worse (higher) in obese adolescents.

How to get and maintain good insulin sensitivity

Insulin sensitivity is highly related to being lean.

Kitavan men, with their low fasting insulin, had an average BMI of 20, the women, 18, compared to 26 for both men and women in Sweden.

Obesity is highly related to insulin resistance, which rises monotonically with increasing body mass index. See chart below. (Source.)

Lean mass, i.e. muscle mass, is associated with better insulin sensitivity. Low muscle mass is associated with insulin resistance, the metabolic syndrome, and diabetes. There’s even a negative feedback loop such that insulin resistance means more muscle loss.

While the relation between carbohydrate intake and insulin resistance is less clear, it is clear that high sugar intake, especially of sugar-sweetened beverages (soda and the like) leads to obesity, which is in turn associated with insulin resistance.

So, to maintain good insulin sensitivity and avoid the diseases of civilization and of aging:

  • stay lean
  • increase and maintain muscle mass
  • avoid sugar.

You can do this by:

  • eating a diet of whole foods, low in refined carbohydrates and sugar, and avoiding processed food
  • lifting weights with intensity and consistency.

See my book, Muscle Up, for more on how lifting weights is one of the healthiest things you can do.

PS: Check out my Supplements Buying Guide for Men.

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  1. bigmyc says:

    Yeah thanx. I just put away two gourmet cupcakes (which I never do) and immediately wondered why I would do such a thing. Rapid heart beat, onset of slight headache and an overall feeling of “weirdness.” And now, here comes your post regarding one of the most elemental tenets of Paleo wellness. It’s like the Paleo cosmos lined up to give a proverbial “slap on the wrist.”

    Anyhow, it’s all good since those aforementioned symptoms leveled out as soon as they came on. A few months ago, my fasting insulin was reportedly 1.6. I was worried that it was too low but it seems to be working for me efficiently enough.

  2. Bill says:

    Thanks PD for the reminder and learning re insulin and glucose.

    My GP said the other day that my fasting glucose and insulin resistance levels are “normal”. I just looked at the paperwork and I am 4.7 mmol/L.. In the middle tertile. ..More fat to get rid of and weights !

    • P. D. Mangan says:

      Hi Bill – note that the study on tertiles of IR used steady state plasma glucose, not insulin, so different units. Your insulin of 4.7 is really quite good.

      • Paloma says:

        Hi PD, How can you convert 3,3 mU/L into mmol/L?
        I would really appreciate it!

        • P. D. Mangan says:

          Hi Paloma, there’s a converter here that converts units for insulin, which is what I assume you had in mind. The conversion differs by substance of interest since each substance has a different molar weight, which is the same as its atomic weight in grams. In this case, 3.3 µIU/mL = 22.9 pmol/L, not the same units you asked for though, but that’s what insulin is usually measured as.

      • Bill says:

        Ta PD ! that’s good to read..
        I struggle with these measurements at times. And especially with Lipid panel measurements. Oz & New Zealand use itheir own system which measures mmol/ liter..

  3. Daniel F says:

    If I may be so bold, I would add a few points to Dennis’ “what you can do” :

    2a: Aside from lifting, consider sprints as well.
    3: Practice intermittent fasting; very effective in getting insulin sensitivity back to healthy levels.

    And, if none of the above seem to be yielding results, or sufficient results:

    4. Get your iron level checked, and bring it down. Elevated iron screws with insulin sensitivity even if your diet and exercise are good.

    Obviously, I am indebted to Dennis’ work to even be able to point out these additional methods!

  4. Joe says:

    P.D., you and I are truly on the same page. We blog about the same issues, as well as specific topics — I also recently have written articles about the importance of lowering blood sugar, the amazing cardiovascular health of the Tsimane tribe (similar story to the Kitaven), preventing cancer and many similar articles focused on extending healthspan.

    Keep up the good work!

    Joe Garma

  5. John says:

    Very true, and infuriating how much and how long we’ve been lied to by nutrition authorities. I am 50 years old, don’t run, and have a 29 inch waist, no health problems and no meds, unlike EVERY patient of mine at my age. Everyone else in my family is fat, as once I was. I eat no sugar, very little grain, cook fish and eggs in avocado oil, ghee, coconut oil, and pork fatback. It drives my friends crazy to see how much fat I eat and stay thin, when they realize I’m not running it off. Every girl I date sees my dietary habits and loses weight by adopting them.

    • P. D. Mangan says:

      Thanks, John. It’s amazing how pervasive is the idea that dietary fat is bad for us. Just about all normal people (“normies”) believe it and can’t be convinced otherwise.

  6. Mike says:

    Inspired by your blog I began a low carb, no refined sugar diet in February, and since May I’m about zero carb and zero sugar. My only carbs are occasional brown rice or whole grain pasta, and sugar is only from fruit or yogurt.

    I did this to start “cutting”, which for me means losing the stubborn visceral fat. At 46 years old it takes a looooong time. The fat came off my limbs and whatnot pretty fast, but losing that fat on the inside, the kind that hides your ab muscles and sabotages the v-taper, takes time.

    I tried I.F. but it didn’t work for me. I also found out the hard way that bulking (during the winter), while enabling more muscle growth, also adds quite a bit of fat. And fat doesn’t go away easy when you’re older.

    So yeah, I’m seeing results with fat loss, finally. The down side is that without carbs I don’t have as much gas in the tank for lifting. I’m not making new gains and I’ve gone down a rep or two in some of my sets. I’d heard this would happen, and that when people go on a cut they reduce the weight a bit, but it’s still frustrating.

    The consolation is to take the long view: In a couple months I’ll really lean, and then I can gradually introduce more (healthy) carbs into my diet to start making gains again.

    • Nick says:

      Hey Mike,

      I’d ask how much sugar you’re taking in daily from yogurt & fruit, and what “occasional” pasta & rice means.

      AFA energy for weightlifting goes, I was amazed when I started doing my lifts and HIIT fasted. Like, I noticed no difference at all in how long or hard I could work. But prior to that, I’d been eating pretty light, and was already (theoretically) fat-adapted.

      In what way didn’t IF work for you?

      • Nick says:

        Erm…eating pretty light before working out, that is, not in general. Like, trying to time it to 2 – 3 hours before the gym, and limiting it to yogurt, quark (sort of like cottage cheese, casein) & whey with berries.

      • P. D. Mangan says:

        I too have never noticed a difference in workout energy levels based on whether I’ve been eating carbs or not. Thing that makes a big difference to me on how well I can exercise is whether I’ve had sufficient time to recover since the last session, and I’ve learned through experience that lifting weights more often than once every 3 days is too much for me.

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