You’ll NEVER reverse insulin resistance until you FIX THIS...

Episode Overview

• This episode explores what insulin and insulin resistance are, why there has been a huge rise in the number of people with insulin resistance (now affecting roughly 25% of the global population), and why normal blood sugar levels can mask severe underlying metabolic issues.
• Professor Rob Semple (Professor of Translational Molecular Medicine at the University of Edinburgh, a board-certified doctor specializing in metabolic health and rare metabolic disorders who has published over 100 papers and discloses no commercial conflicts or funding ties) joins the host (a co-founder/representative of ZOE Science & Nutrition).
• The conversation traces insulin's vital role in human survival—from its 1922 discovery to how it regulates glucose, fat, and protein—before debunking social media myths that demonize the hormone.
• Listeners learn why BMI is a flawed predictor of metabolic health, how personal fat-storage limits and visceral fat drive insulin resistance, and what hidden physical signs (such as PCOS and skin changes) indicate high insulin.
• The episode concludes with evidence-based strategies to improve or reverse insulin resistance through diet, exercise, sleep, and stress management, alongside a mid-roll promotion for ZOE's commercial gut health products.

Key Concepts

• Insulin's Essential Role and History: Insulin is arguably the most important hormone in the world, acting as a chemical messenger sending signals from one bit of the body to the rest. Because humans eat episodically while key organs (brain, heart, kidneys) need constant energy, insulin smooths out the energy supply. Before insulin was purified and injected around 1922, Type 1 diabetes was a death sentence leading to wasting away and death over 2 years (with a starvation diet buying only a few extra months); after 1922, skeletal children recovered in a few months, leading to Nobel prizes and standing ovations on the London Stock Exchange.
• How Insulin Manages Energy Across Tissues: Glucose is the simplest fuel and the main currency of metabolism, especially for the brain; if blood sugar drops too low, the brain malfunctions, causing confusion, unconsciousness, and seizures. Insulin regulates glucose via negative feedback and only lasts in the bloodstream for a few minutes. When circulating, it triggers fat cells (which are balloons full of fat with a tiny rim of apparatus) to take up sugars and fats, tells the liver to stop making glucose and stop burning emergency fuels, directs muscles, liver, and kidneys to store smaller energy supplies as glycogen, and stimulates tissue growth.While blood glucose gets the most attention because it makes you feel unwell fastest if it goes wrong, insulin's regulation of fat and protein metabolism is just as important for long-term health.
• Debunking Social Media Myths & Glycemic Spikes: Social media claims that we should keep insulin as low as possible have strands of truth, but Semple notes they are given a degree of weight and precision they do not deserve; keeping insulin down is simply a scientific-sounding way of saying to be lean, healthy, and eat complex foods. Processed carbohydrates (soda, white bread, pizza base, white rice) digest rapidly—the host notes white bread causes an extraordinary blood sugar spike in 15 minutes comparable to a can of Coke unless eaten with fat and protein—demanding a huge, rapid insulin spike. About 1 to 2 hours later, an "overshoot" downwards in blood glucose can leave people feeling wobbly, sweaty, and tremulous. Complex carbs (like brown rice) digest slowly, spreading insulin release over a longer period.
• "Pure" Insulin Resistance and Global Prevalence: In insulin resistance, insulin's signal to fat, muscle, and liver is blunted. The pancreas compensates by producing much more insulin, maintaining normal blood sugar for a long time before eventually getting "tired," which is when blood sugar rises into Type 2 diabetes (causing toxic microvascular complications in the eyes, kidneys, and nerves, which is why diabetics have their eyes photographed every 1 or 2 years, feet examined, and urine tested). Having normal blood sugar maintained by very high insulin is "pure insulin resistance." The biggest global studies show it affects about a quarter (25%) of the world's population, varying by country and ethnicity from 10% to 50%, and sitting at 20% to 30% in the US and UK.
• Hidden Risks and Tissue Over-Response: Even with normal blood sugar, insulin resistance increases the risk of heart disease and is almost always associated with low HDL ("good") cholesterol and high triglycerides. While muscle and liver resist insulin, other tissues remain sensitive and over-respond to high insulin levels. In the skin, this triggers darkening, browning, and thickening in creases (neck, armpits, under breasts, groin) and multiple skin tags around the neck. In the ovaries, high insulin disrupts monthly hormone choreography, causing larger ovaries, excess male-type hormones, irregular ovulation/bleeds, extra hair growth, and reduced fertility—a condition known as PCOS, recently renamed Polyendocrine Metabolic Ovarian Syndrome. Big population studies over decades also show an increased risk of certain cancers, though Semple hedges that these are "very marginal risks." Conversely, Semple takes online claims blaming brain fog, cravings, and post-meal fatigue on insulin resistance "with a pinch of salt," calling it simplistic and hard to separate from confounders like midlife responsibilities, weight gain, and menopause.
• The BMI Paradox and Fat Storage Thresholds: Extensive studies show insulin resistance does not only affect people with excess weight. While a family tendency toward obesity is about the brain and energy balance, whether weight gain causes metabolic complications depends on how good your body is at making healthy fat tissue. When fat cells reach their expansion limit, they become damaged and inflamed, sending unhealthy fats into the liver. Population studies show storing fat on the lower body (thighs and bottom) is healthy and lower risk, whereas a middle-heavy body with thin legs carries high risk. The host shares that a DEXA scan from an early ZOE trial revealed he had high visceral fat around his organs; Semple explains that visceral fat (inside the belly) is a harmful "second-level energy reserve" with preferential access to the liver, dumping fat straight into it. However, Semple notes the scientific community is only just beginning to understand why different fat depots behave so differently.
• Lifestyle Mechanisms (Exercise, Stress, and Sleep) & Evolutionary Roots: Reversing insulin resistance is possible even with strong genetic predispositions. Semple confidently expects that improving insulin resistance reduces heart disease and diabetes risk, though he pauses to hedge that he is relying on his experience and beliefs while wondering where the large-scale trial evidence is on that specific point. Exercise bypasses insulin resistance because working muscles absorb and burn glucose without needing insulin; Semple notes comparative evidence between aerobic and resistance training is "somewhat piecemeal," though long aerobic sessions excel at biochemical changes and resistance training builds muscle size. Sustained stress (illness, injury, life events) and chronic sleep deprivation raise natural steroids, growth hormone, and adrenaline-like hormones, which increase insulin resistance and shift fat to unhealthy depots. Circadian disruption from shift work, electric light, or time zones adds an extra layer of challenge, though Semple hedges he wouldn't overestimate its effect. Evolutionarily, the 25% of people prone to insulin resistance may have had a survival advantage in hunter-gatherer times, such as restarting fertility faster when food returned after a famine.
• Disclosed Commercial Ties and ZOE Research: During a mid-roll advertisement, the host promotes ZOE's commercial gut health test and app, stating ZOE used data from 300,000 gut health/microbiome tests over 8 years to build the world's largest microbiome DNA database and proprietary AI. He cites a randomized controlled trial published in Nature Medicine "last year" showing ZOE app users significantly improved across health measures compared to a control group, and shares that after 10 days of antibiotics reduced his gut to 6 of the 50 "good bugs," following ZOE's advice brought him up to 23.

Quotes

• At 2:32 - "Insulin is a rapidly changing, complex hormone that can go wrong in many different ways, and trying to package it all into one thing called insulin resistance is often misleading." - Framing the complexity of metabolic health at the start of the episode.
• At 9:49 - "And that is because that's the thing which makes you feel unwell fastest if it goes wrong." - Explaining why medicine and culture fixate on blood glucose even though insulin's regulation of fat and protein is equally important long-term.
• At 13:55 - "Insulin is essential for life, so to demonize insulin clearly doesn't make any sense. And the best way to minimize your insulin, to make it as low as possible, is to be borderline starved, which is clearly not a way to live life and causes a lot of untold misery." - Refuting social media influencers who claim insulin should be kept as low as possible at all times.
• At 21:00 - "In other words, if you have a normal sugar level, but you require a very high insulin level to maintain that, that is pure insulin resistance." - Defining how severe insulin resistance hides behind normal routine blood glucose tests.
• At 28:06 - "What we know from very extensive studies now is that some people can carry a huge amount of extra weight, some people can move into the very obese range and really have not much in the way of insulin resistance or metabolic complications, whereas some people can still be in the normal weight range, but as they gain weight within that range, they can begin to get those complications." - Explaining the BMI paradox and personal fat thresholds.
• At 30:28 - "The ovaries, because they're so sensitive to high levels of insulin, almost are like a canary in the coal mine." - Highlighting how PCOS symptoms serve as an early warning sign of insulin resistance in women that men lack.
• At 35:57 - "So it's absolutely crucial to understand that no matter what the cause of your insulin resistance is, there is a lot that you can do to improve it by the way you eat, the way you exercise, and the way you lead your life." - Emphasizing that genetic predisposition to insulin resistance is not destiny.
• At 38:27 - "Whether or not you have a family tendency towards obesity is about the brain and about your energy balance. If you accumulate weight, if you become obese, whether or not you get the metabolic complications is about how good you are at making fat tissue." - Clarifying the biological difference between gaining weight and developing metabolic disease.
• At 43:17 - "So muscles use glucose as one of their favorite fuels, and they are able to use glucose, they're able to use sugar when they're exercising even without requiring insulin at all. So it's a way to get rid of sugar and to burn it without stressing the insulin side of things at all." - Explaining the direct mechanism by which physical activity clears blood sugar.

Takeaways

• Look beyond blood sugar and BMI to assess your risk: Because gene variant panels don't yet do a much better job than clinical history, evaluate your personal risk by checking your family history (older relatives with Type 2 diabetes or female relatives with gestational diabetes), your body shape (storing weight around the middle with thin legs vs. on the hips and thighs), blood lipid panels (high triglycerides and low HDL cholesterol), and physical signs like neck skin tags, darkened skin creases, or PCOS symptoms.
• Swap processed carbohydrates for complex, whole foods and balanced meals: Avoid rapidly absorbed carbs like soda, white bread, white rice, and pizza bases that trigger massive insulin spikes and subsequent blood sugar crashes 1 to 2 hours later; instead, choose complex carbohydrates like brown rice, reduce harmful dietary fats that interfere with insulin function, or pair carbs with protein and fat to slow digestion.
• Combine aerobic and resistance exercise at any duration you can manage: Ignore influencer claims that you need 2 hours in the gym 5 times a week—there is no minimum threshold of exercise required to get a benefit, and any movement helps muscles burn glucose without needing insulin. Aim for a mix of long aerobic exercise (to drive biochemical improvements) and strength training (to build glucose-consuming muscle mass).
• Target visceral belly fat even if your overall weight is "normal": If you gain weight around your midsection, focus on lifestyle changes to prevent overloading your personal fat storage threshold and accumulating visceral fat around your organs, which dumps harmful fats directly into the liver.
• Protect your sleep and manage chronic stress: Prioritize consistent sleep routines and stress reduction to prevent chronic elevations in natural steroids, growth hormone, and adrenaline-like hormones that drive insulin resistance and abdominal fat storage, especially if you face circadian disruptions from shift work or crossing time zones.