Early Warning Signs of Chronic Disease

Doctors can now spot the slide toward diabetes years before a standard blood test would ever flag it, using a handful of simple checks most patients never get offered.

Quick Take

Dr. Chris Thompson, a Harvard Medical School gastroenterologist, and Stanford neuroscientist Dr. Andrew Huberman discussed a step-by-step pattern of metabolic decline on the Huberman Lab Clips channel.
They say fasting insulin, waist-to-height ratio or a DEXA scan, continuous glucose monitoring, and breath-based gas exchange testing can catch trouble earlier than standard diabetes markers.
Outside research shows fasting insulin and waist-to-height ratio have real backing, while continuous glucose monitors remain more debated for people who don’t have diabetes.
The conversation pushes a bigger idea: don’t wait for a diagnosis. Catch the warning signs while they’re still fixable.

The Pattern Doctors Say Most People Miss

Thompson and Huberman laid out what they call a predictable sequence of metabolic dysregulation. The body doesn’t jump straight from healthy to diabetic. It moves through stages, and each stage leaves clues. The problem, they argue, is that most doctors only test for the last stage, fasting glucose, by which point the damage has been building for years.

Thompson brings a heavyweight resume to the conversation. He’s chief of interventional gastroenterology at Mass General Brigham in Boston and co-directs a center focused on weight management and metabolic disease. That clinical background is why his framing carries weight beyond typical podcast chatter.

Four Tools That Catch Problems Earlier

The doctors point to four specific tests. First is fasting insulin, which can rise long before blood sugar looks abnormal. Second is waist-to-height ratio or a DEXA scan, both of which measure fat distribution rather than just weight. Third is a continuous glucose monitor, which tracks sugar swings throughout the day. Fourth is breath-based gas exchange testing, which looks at how the body burns fuel.

None of these tools are exotic. A waist-to-height ratio only requires a tape measure and a calculator. Continuous glucose monitors are now sold without a prescription in many states. The point Thompson and Huberman make isn’t that these tests are hard to get. It’s that they’re rarely offered before a person already has a diagnosis.

What The Broader Research Actually Shows

Fasting insulin has real support in the medical literature as an early signal of insulin resistance, sometimes showing up before any other marker changes. But other reviews caution it isn’t perfect. One analysis found fasting insulin doesn’t always match up with gold-standard lab measures of insulin sensitivity, meaning it can mislead if used alone.

Waist-to-height ratio has stronger consensus behind it. A ratio above 0.5, meaning your waist is more than half your height, is now used as a simple screening cutoff in national health guidelines, including recommendations from Britain’s National Institute for Health and Care Excellence. Researchers across multiple studies have found it performs as well as or better than waist circumference alone for predicting cardiometabolic risk.

Continuous glucose monitors are the most contested piece of this puzzle. Harvard Medical School notes there’s still no solid evidence these devices improve health in people who don’t have diabetes. Yale researchers have gone further, saying there’s little to no research on what glucose spikes even mean in healthy people, and they don’t recommend routine use outside a diabetes diagnosis. Other newer reviews push back, arguing continuous monitoring can reveal abnormal glucose patterns early and support personalized lifestyle changes before a formal diagnosis arrives.

Why This Matters For Anyone Over 40

This debate isn’t academic for anyone watching their own health numbers creep in the wrong direction. Waiting for a fasting glucose test to flag diabetes means waiting until the disease has likely been progressing for years. Thompson and Huberman’s argument, tested against the research, holds up reasonably well for fasting insulin and waist-to-height ratio. The continuous glucose monitor piece deserves more scrutiny before anyone treats it as gospel.

Cheap, simple measurements like a tape measure around your waist cost nothing and carry real backing. Newer technology like glucose monitors might help, but the science hasn’t caught up with the marketing yet. Patients should ask their doctors about the tools with proven track records first, and treat the rest as promising but unproven.

The bigger takeaway from this conversation is less about any single test and more about mindset. Chronic disease doesn’t arrive overnight. It builds quietly, and the tools to catch it early already exist. The question is whether the health system starts using them before diagnosis instead of after.