In my previous post Traditional Food*, I explained how what we think of as a "traditional" diet is a nationalist propaganda campaign that's making us sick. In this post I'll go into the biological mechanisms.

There are four substances that the body can metabolize: carbohydrates, fats, protein and alcohol. Of these, I'll focus on how modern carbohydrate-heavy foods (like pasta, bread and rice) are related to insulin resistance. This doesn't mean that seed oils are good for you, or that the industrial revolution hasn't changed how people consume meat. Seed oils are bad for you and people today don't eat meats the way peasants did—they ate organs and other stuff that gets fed to animals today. Alcohol is just a poison you can metabolize.

With that out of the way, it's time to learn about insulin resistance.

Insulin & Resistance

Your blood has glucose dissolved in it. Blood glucose is important because your brain relies on glucose to function. If there wasn't glucose in your blood, then you'd die. However, too much blood glucose causes problems too. Precisely what problems hyperglycemia causes isn't important right now. Instead, what matters to this post is that your body has a control system that keeps your blood glucose in its proper range.

When your blood glucose rises, your body releases a hormone called insulin. Insulin binds to insulin receptors in cell membranes. These insulin receptors activate signalling that tells various tissues in your body that it's time to absorb that glucose from the blood and into cells.

Your blood glucose spikes (rises very fast) when you eat foods that release lots of glucose quickly. Foods that quickly release lots of glucose into your bloodstream are said to have high glycemic index. White rice and anything made out of modern flour has a high glycemic index. Sugary drinks have a very high glycemic index. Slower-digested foods like legumes have a low glycemic index.

When you eat foods with a low glycemic index, this system works fine. But when you eat foods with an unnaturally high glycemic index, the system works badly. The unnaturally high glucose spike causes an evolutionarily unprecedented insulin spike. The blood glucose then drops below where it's supposed to be. In this way, eating too much high-glycemic food actually makes you hungrier. That hunger creates a caloric surplus, which leads to obesity.

Even worse, repeated insulin spikes cause the insulin receptors to desensitize (downregulate) themselves. Your body creates more insulin to get the attention of desensitized receptors. This produces a horrible chain reaction where your insulin is chronically high and the cellular response diminishes. This is insulin resistance. So insulin resistance prevents fat burning too, because insulin inhibits fat release. Here are some signs of insulin resistance.

• Disproportionate accumulation of fat in your belly relative to the rest of your body.
• You feel tired 30–120 minutes after eating. In bad cases you may even nap after eating.
• Energy drops when you skip meals, but cognitive and physical performance rebound strongly 2–3 hours (or even the next day) after a meal.
• You bonk (run out of energy) when you attempt long-distance endurance exercise without consuming carbs.

Perhaps this is happening to you and you think it's normal, or just part of getting old. It's not! The reason it might seem normal to you is because most ^[[1]] Americans—even non-obese Americans—have a sign of metabolic dysfunction like this. 38% meet the much worse criterion of prediabetes. This is historically unprecedented. Ignoring tiny aristocratic minorities, no society before 1800 was like this. If you're eating three meals per day, your energy levels should be mostly decoupled from when you eat. Your hunger should be decoupled from your energy levels too.

Many factors led to this, including exercise patterns (mostly driven by horrific urban planning), stress, and electric lights. But the most important factor is probably diet.

How diet changed

Historically, most of what normal people ate had—by modern standards—a very low glycemic index. Even milk and honey, foods so valuable the Bible uses them to paint a picture of the Promised Land, have only low-to-medium glycemic indices.

[These tables come from ChatGPT because the details aren't important—just the general trends.]

When you look at these tables, you'll notice two major trends.

• Tastier food has higher glycemic index.
• Processing a food increases its glycemic index. Modern processing increases its glycemic index even more.

Historically, insulin resistance was overwhelmingly a disease of the rich (and sometimes monks), because only the rich could afford the tasty foods that cause insulin resistance. Historical societies were so extremely unequal that almost nobody was rich. Consequently, almost nobody got insulin resistance.

Today, modern technology allows everyone to eat like a medieval king. The cheapest bread in your local grocery store has a glycemic index that historically, only the rich could afford.

1. Epidemiological data shows 10%-15% of Americans as having normal metabolic markers. The exact numbers vary depending on where you put semi-arbitrary cutoffs. If we used a reference class of hunter-gatherers, then American metabolic health would look even worse. Unfortunately, precise data on hunter-gatherers' metabolic markers is much harder to come by. ↩︎