Issue #11: Fasting insulin, the number that breaks first

Most men over 40 get their blood sugar checked, see a normal result, and move on. The trap is that fasting glucose is the last thing to break, not the first. By the time it climbs, the engine has been running hot for years.

There is an earlier number. It is cheap, it sits on most lab menus, and almost nobody orders it: fasting insulin. It can show trouble a decade before your glucose blinks.

Here is what it is, why it goes bad first, and how to pull it back down, every claim graded.

Fasting insulin is exactly what it sounds like: how much insulin is floating in your blood after an overnight fast. Insulin is the hormone that moves sugar out of your blood and into your cells. When those cells stop listening, which is what insulin resistance is, your pancreas does the obvious thing. It shouts louder. It pumps out more insulin to force the same job done.

Here is the catch. That extra insulin keeps your blood sugar looking normal. So your glucose and your HbA1c can sit in the healthy column for ten to twenty years while your insulin runs maxed out behind the scenes (strong evidence). Fasting glucose is the smoke alarm that finally goes off. Fasting insulin is the wiring that was overheating the whole time.

Checking only glucose is like judging a car by whether the check-engine light is on. Useful, but late.

This is where it gets almost funny. The standard lab range for fasting insulin runs up to about 25. So a result of 20 comes back unflagged. No phone call, no follow-up, nothing. But the range metabolically healthy people live in, and that longevity-minded doctors aim for, is under 5 to 8, with the sweet spot closer to 2 to 5 (moderate evidence, this is a functional target rather than a formal guideline cutoff).

Run the math and it gets worse. There is a simple score called HOMA-IR that combines your fasting insulin and fasting glucose. Optimal is under 1. A man with a spotless fasting glucose of 95 and a normal fasting insulin of 18 scores a 4.2. That is not borderline. That is established insulin resistance, hiding behind two numbers that each looked fine on their own.

The whole point of this newsletter in one line: normal is the average of a sick population. Optimal is where you actually want to live.

High insulin is not just a diabetes precursor. In men, it tracks with the things that actually end people. In the Helsinki Policemen Study, almost a thousand healthy middle-aged men followed for 22 years, high fasting insulin predicted coronary heart disease largely on its own, independent of the usual risk factors (strong evidence). It has turned up as an independent marker for heart disease in more than one large cohort.

It also makes the rest of your 40s harder in a way you never see on a glucose test. Chronically high insulin is a storage signal. It tells your body to hold onto fat, especially around the middle, and it defends that fat against being burned. It is a tailwind for gaining weight and a headwind against losing it. If you have been eating clean and training and the belly will not move, this is one of the first places I would look before blaming your willpower.

The good news is that fasting insulin responds fast, often faster than the scale. What moves it:

Cut the refined carbs before you cut the calories. Sugar and refined starch are the single biggest spike to insulin, and pulling them back produces the largest short-term drop in fasting insulin and HOMA-IR, more than just eating less of everything (strong evidence). You do not need full keto. You need less bread, soda, and dessert, and more protein and fiber on the plate.

Move after you eat. A ten to fifteen minute walk after a meal blunts the insulin that meal demands. Stack that on resistance training, which teaches your muscles to pull sugar out of the blood without needing as much insulin to do it (strong evidence). Muscle is metabolic real estate. More of it means a lower insulin bill, which is a nice bridge from the last issue.

Lose the visceral fat, not just the weight on the scale. The fat packed around your organs is the fat that drives insulin resistance. As it comes off, sensitivity climbs (strong evidence).

Sleep like it counts. Even a few nights of short sleep measurably worsens insulin sensitivity in healthy people (moderate evidence). It is the free lever almost everyone skips.

Here is my confession on this one. For years I did the exact thing this issue is warning you about. I checked my glucose, saw “normal,” felt smug, and moved on. Nobody ran my fasting insulin, and it never occurred to me to ask, because who checks the wiring while the smoke alarm is quiet.

Then I asked for it. You would think I had requested a werewolf panel. I have been through something like eight clinics, and most of them read a lab report like a scratch-off ticket: glance, see nothing screaming, move on. When I asked one to add fasting insulin, the doctor actually said, “your glucose is fine, why do you want that.” Because my glucose being fine is the whole trap, my guy. We had a brief philosophical standoff next to the blood pressure cuff. I won, mostly by being annoying, which is my primary cardio.

The number came back lower than I had any right to expect, which makes it the single most optimal thing about me. I would love to credit some genius protocol. The honest version is that I lift, I eat enough meat to unsettle a vegetarian, I skip most of the bread, and a while back a tesamorelin run quietly evicted the belly fat that drives this whole problem. My waist went from a 32 to a 28 and dragged my insulin down with it. My abs are still more of a rumor than a fact, but now the bloodwork corroborates the rumor.

So no, I did not earn a good fasting insulin through monk-like discipline. I earned it by being suspicious of “normal,” annoying a doctor until he caved, and accidentally doing three right things while chasing completely unrelated goals. If I can back into this number sideways, you can walk up and take it on purpose.

This is the whole reason the newsletter exists. The lab hands you a column called normal and lets you assume you are fine. Fasting insulin is the cleanest example there is of a number that sits inside normal and is still costing you.

See where your own numbers actually land, not just whether you cleared the lab’s floor. The free Normal vs Optimal tool and bloodwork cheat sheet walks through this one and the rest: labs.the40protocol.com

And if your doctor will not order a fasting insulin, that tells you something too. Hit reply and tell me what your labs have been hiding.