The body is not a calculator

Why your metabolism shifts more quietly than your weight ever reveals

We trust what we can measure. A number on the scales. A value on a test result. A face in the mirror. It feels honest: one figure, in black and white, telling us exactly where we stand, as though the body reads its truth aloud.

But the body is not a reader. It is a bookkeeper that works in silence, and it writes its most important figures years before anyone asks to see them. A calculator gives you a single answer. A body keeps dozens of accounts at once, in a language you cannot see. And it is precisely in that gap that most of our misunderstandings about health begin.

We believe what we can measure

There is something seductive about a single number. It is tidy. It promises control. But a single number is always a summary, and summaries leave things out.

The scales tell you how heavy you are, not what that weight is made of. A blood value tells you how things stood at one moment, not which way you have already been drifting for years. And the mirror shows the outside, while the story that matters plays out within. We read the one number and believe we have read the whole book.

What insulin actually does

To understand what is happening underground, we need to talk about insulin. But not in the way you usually hear it.

Insulin is not a “sugar-lowerer”. It is your body’s storage manager.¹ After a meal, insulin decides where the energy goes: burned now, stored in muscle, or kept as fat for later. It is a hormone that arose to help us survive, in a world where the next meal was never certain. It keeps. It protects. It is, in short, a friend. Until it has to work too hard.

The quiet years

Here lies the heart of this story, and it is what almost no one tells you.

Long before anyone is told “diabetes” or even “prediabetes”, the body is already shifting. In a large British study, thousands of people were followed for years. Among those who eventually developed diabetes, the metabolism was found to be changing three to six years earlier, while blood sugar still looked largely normal.²

What happens is almost moving to watch. First, the body grows less sensitive to insulin. The pancreas notices, and does what a loyal worker does: it makes more insulin, harder, to keep blood sugar normal anyway. For a while it succeeds. The test stays tidy. And then, after years of overtime, it becomes exhausted, and only then does blood sugar begin to rise.²

In other words: the body whispers long before it shouts. The rising insulin is the whisper. The rising sugar is the shout. And most tests only listen for the shout.

Why a normal result can mislead

This is not a plea for fear. Most people with a normal value are simply fine, and the point is not to start eyeing your blood results with suspicion.

It is a plea for humility about what a single number shows. One fasting blood sugar is a photograph, not a film. It captures a moment, not the direction you have been moving in for years. That is exactly why a doctor looks at the bigger picture, at patterns over time, at several signals together.³ It is also precisely why this is not something to judge for yourself: seeing the pattern is work for you and your GP together, not for a set of scales or a lone value.

The woman at the dinner

A few years ago I sat next to a young woman at a dinner. Slim, sporty, recently and noticeably slimmer. Everyone complimented her; her mother glowed. A little later she passed me, and very softly, so no one would hear, she said: “The GP says I have prediabetes.”

I looked at her in surprise. Prediabetes? She had become so slim.

And yet it happens. About one in five people of normal weight is not metabolically healthy, with a more than threefold higher risk of heart and vascular problems.⁴ Often there is little muscle on the body and a good deal of fat in the places you cannot see: around the organs and in the liver.⁴ Slim on the outside, strained within. Her outside, like the scales, was also just one number, and it did not tell the whole story.

Insulin touches more than sugar

And that story is larger than diabetes alone. Because when insulin runs too high for years, it affects more than your blood sugar.

It touches the liver, which can begin to store fat where it does not belong.⁴ It touches the blood vessels, and with them the heart. And it plays a leading role in PCOS (polycystic ovary syndrome), a common hormonal condition in women, in which that same “insulin working too hard” turns out to be an important driver. Insulin, then, is not a sugar dial. It is more like a conductor who shapes the whole orchestra of your metabolism, and when he has to conduct too loudly, you eventually hear it everywhere.

What this means for you

No panic, and no war on carbohydrates. But a few things do make a difference, and they help the quiet system rather than shouting it down.

Move after eating. This may be the loveliest piece of physiology in the whole story. Your muscles can draw sugar out of your blood even without much insulin, they have their own little door that opens the moment you use them.⁵ A short walk after a meal is therefore no small detail; it is your muscles briefly taking over insulin’s work. And whoever trains regularly enlarges that capacity for good.⁵

Trust the food-order trick, but only so far. Perhaps you have heard it: vegetables and protein first, carbohydrates last, to soften your blood sugar peak. It is true, a little. But the studies behind it are small (sixteen, twenty-five, eighteen participants) and short, and the effects are modest. It is a nice nudge, not a treatment. Do not mistake a small lever for the whole machine.

Know your pattern, not your snapshot, and discuss it with your GP. That is where the real information lies.

And if you want to know how to lose weight without losing muscle, because muscle is your greatest ally in this whole story, I wrote about that at length in Diets: What Really Works?.

In closing

Health is not a number you read off. It is a pattern over time, one that unfolds largely unseen. The scales, the mirror, that single value, each tells a sliver, and none of them the whole.

The body is not a calculator. It does not calculate; it chooses, it keeps, it protects, and it keeps its books in silence. Perhaps the deepest wisdom is to learn to listen a little more softly, to the whisper, long before anything shouts.

Which quiet signal, in your body, or somewhere else in your life, have you lately mistaken for the whole story?

Related reading

• Diets: What Really Works? The Honest Truth About Losing Weight
• The liver: the organ the ancients revered and we forget
• Cholesterol: the building material of your life
• Menopause: Your Body Isn’t Broken. It’s Recalibrating.
• Don’t wait for a diagnosis to learn what health is worth

---

Notes

1. Insulin as a storage hormone. After a meal, insulin governs how energy (glucose) is taken up and stored in muscle, liver and fat tissue; “lowering blood sugar” is a consequence, not the whole function.
2. Compensatory hyperinsulinaemia. This is the phase in which the pancreas (the beta cells) makes extra insulin to compensate for falling insulin sensitivity, so that blood sugar stays normal for a time.
3. Snapshot versus pattern. A single fasting glucose measures one moment; measures such as HbA1c or repeated tests show the course over time.
4. Visceral and liver fat. Fat around the organs and in the liver is metabolically more active and riskier than fat under the skin; “metabolically unhealthy at a normal weight” describes slim people with this profile.
5. GLUT4. The “door” (transport protein) through which muscles take up glucose; muscle contraction opens this door, partly independently of insulin.

Disclaimer

This article shares general science, not personal medical or nutritional advice. If you have symptoms, abnormal blood values, or anything involving hormones, weight or medication, please discuss it with your GP or a treating specialist. They can look at your situation, a blog cannot.

---

Sources

The numbers below follow the order in which the studies appear in the text. All sources were verified via PubMed.

1. Tabák, A. G., Jokela, M., Akbaraly, T. N., Brunner, E. J., Kivimäki, M., & Witte, D. R. (2009). Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: An analysis from the Whitehall II study. The Lancet, 373(9682), 2215–2221. https://doi.org/10.1016/S0140-6736(09)60619-X
2. Stefan, N., Schick, F., & Häring, H.-U. (2017). Causes, characteristics, and consequences of metabolically unhealthy normal weight in humans. Cell Metabolism, 26(2), 292–300. https://doi.org/10.1016/j.cmet.2017.07.008
3. Zhao, H., Zhang, J., Cheng, X., Nie, X., & He, B. (2023). Insulin resistance in polycystic ovary syndrome across various tissues: An updated review of pathogenesis, evaluation, and treatment. Journal of Ovarian Research, 16(1), Article 9. https://doi.org/10.1186/s13048-022-01091-0
4. Richter, E. A., & Hargreaves, M. (2013). Exercise, GLUT4, and skeletal muscle glucose uptake. Physiological Reviews, 93(3), 993–1017. https://doi.org/10.1152/physrev.00038.2012
5. Sun, L., Goh, H. J., Govindharajulu, P., Leow, M. K.-S., & Henry, C. J. (2020). Postprandial glucose, insulin and incretin responses differ by test meal macronutrient ingestion sequence (PATTERN study). Clinical Nutrition, 39(3), 950–957. https://doi.org/10.1016/j.clnu.2019.04.001
6. Murugesan, R., Kumar, J., Thiruselvam, S., Leela, K. V., Geetha, K., Satheesan, A., Chaithanya, V., & Angelin, M. (2024). Food order affects blood glucose and insulin levels in women with gestational diabetes. Frontiers in Nutrition, 11, Article 1512231. https://doi.org/10.3389/fnut.2024.1512231
7. Higuchi, Y., Miyawaki, T., Kajiyama, S., Kitta, K., Kajiyama, S., Hashimoto, Y., Fukui, M., & Imai, S. (2025). Dietary modification with food order and divided carbohydrate intake improves glycemic excursions in healthy young women. Nutrients, 17(20), Article 3194. https://doi.org/10.3390/nu17203194

Sources on this site are cited in APA style, with a DOI wherever one exists. Why I made that choice →