Robert Lufkin, MD: The NYT Bestselling Author on Metabolic Health, Prevention, and What Your Doctor Isn’t Testing

Dr. Robert Lufkin spent decades as a full professor at both UCLA and USC Schools of Medicine, authoring over 200 peer-reviewed papers on metabolic health and longevity. 

He was, by every conventional measure, one of the people who knew best how to stay healthy. Then his own health fell apart - and the experience led him to question almost everything he had spent his career teaching.

His New York Times bestselling book Lies I Taught in Medical School makes the case that metabolic dysfunction is the common root cause connecting most of the chronic diseases we die from, and that the system designed to treat them is built around the wrong model. 

We asked him about fasting insulin, the longevity supplements not worth your money, and what mainstream medicine will finally accept within the next decade.

1. You were a medical school professor teaching the very things you now challenge. What was the specific moment or diagnosis that made you stop and question everything?

It wasn't one moment - it was four diagnoses arriving almost at once. I'd spent decades as a medical school professor at UCLA and USC, writing hundreds of research papers, teaching medical students, and doing what I believed was everything right. I followed the food pyramid. I exercised. I got my annual checkups. And then, seemingly out of nowhere, I was diagnosed with type 2 diabetes, hypertension, gout, and dyslipidemia - the full constellation of metabolic syndrome. These were diseases my own father hadn't developed until his eighties. I was decades younger. When I brought these diagnoses to my doctors, the answer was straightforward: take these medications for the rest of your life. That was the moment. Because I realized that I, a medical school professor, had been both the teacher and the patient of a system that couldn't explain how someone doing "everything right" ended up this sick - and had no plan to actually fix it.

2. You reversed four chronic diseases in yourself through lifestyle changes. Walk us through what those first 90 days actually looked like. What did you change, in what order, and what improved first?

The first thing I changed was nutrition - specifically, I eliminated refined carbohydrates, sugar, and industrial seed oils. That was week one. I shifted to a lower-carb, higher-healthy-fat approach, focusing on whole, unprocessed foods. Within the first few weeks I also started incorporating time-restricted eating - cutting out snacking and compressing my eating window. Sleep and stress management came next. I became much more intentional about both. In terms of what improved first, blood pressure responded the fastest - within weeks it started coming down noticeably. Blood sugar followed. By the end of about 90 days, my lab numbers had changed so dramatically that my doctors thought there was a mistake - they actually wanted to re-run the labs because they didn't believe the results. Eventually they discontinued my prescriptions. All four conditions went into remission through lifestyle alone. No medications. 

The order I'd recommend: fix what you eat first, then when you eat, then optimize sleep, stress, and movement. Each layer amplifies the others.

3. Most of our readers already track biomarkers and experiment with their health. What's the one metabolic marker you think even experienced health optimizers are overlooking or misinterpreting?

Fasting insulin. Most people - even serious health optimizers - track fasting glucose and maybe hemoglobin A1C, but almost no one asks for fasting insulin. And most doctors don't order it. Here's the problem: insulin resistance develops years or even decades before glucose ever goes out of range. Your fasting glucose can look perfectly normal while your insulin is working overtime to keep it there. By the time glucose rises, you've already been metabolically dysfunctional for a long time. A fasting insulin level ideally should be below 5 µIU/mL. Many people walking around with "normal" bloodwork are sitting at 10, 15, or higher, and nobody flags it. If you're only looking at glucose, you're seeing the smoke after the house is already on fire. Start tracking fasting insulin - it's the earliest warning signal we have for metabolic dysfunction.

4. Your book makes the case that metabolic dysfunction connects most chronic diseases. For someone who looks healthy on paper (lean, active, decent bloodwork), where does metabolic dysfunction hide?

This is one of the most important questions people can ask, because metabolic dysfunction is not just an obesity problem. Studies suggest that 80 to 90 percent of American adults have at least one marker of metabolic dysfunction. Many of these people are lean. They exercise. Their standard bloodwork looks fine. But metabolic dysfunction hides in places conventional panels don't look: elevated fasting insulin (as I mentioned), chronic low-grade inflammation (hsCRP), visceral fat that doesn't show on a scale, early fatty liver that never gets screened, and subtle insulin resistance masked by a pancreas still working hard to compensate. It also hides in the brain - neuroinflammation can be present long before any cognitive symptoms appear. The standard annual physical was never designed to catch metabolic dysfunction early. It was designed to catch disease after it's already established. If you look healthy on paper but you're eating a standard modern diet heavy in refined carbs, seed oils, and ultra-processed foods, the dysfunction is likely already building beneath the surface.

5. Fasting, ketogenic diets, mTOR inhibition - you cover all of these. For a busy founder or executive optimizing for both cognitive performance and longevity, how do you think about sequencing these interventions?

I'd start with nutrition as the foundation - specifically, eliminating the metabolic disruptors first: refined sugar, flour, and industrial seed oils. That alone moves the needle more than most people expect. Once nutrition is clean, layer in time-restricted eating. Even a 16:8 pattern gives your body time to lower insulin and activate repair pathways. For executives, this often improves mental clarity and sustained energy more than any nootropic. After those habits are stable - usually a few weeks - you can explore deeper fasting protocols. A periodic 3-day water fast, for example, activates autophagy, resets the immune system, and powerfully inhibits mTOR, which is the master growth switch that when overactivated accelerates aging and disease. For ongoing mTOR management, a well-formulated lower-carb or ketogenic diet keeps mTOR signaling in a healthy range most of the time. Some people also explore low-dose rapamycin under physician supervision - I take it myself for longevity. The key insight is that these interventions aren't competing strategies. They're layers of the same metabolic optimization: nutrition first, meal timing second, periodic deeper fasts third, and pharmacological tools like rapamycin as an optional fourth layer for those who want to go further.

6. Many of our readers have had the experience of bringing research to their doctor and getting pushback. When your own physician disagrees with a lifestyle-first approach, how do you recommend navigating that conversation without damaging the relationship?

First, understand where your doctor is coming from. Medical schools provide very little nutrition education - sometimes just a few hours across all four years. Physicians are trained in a system that overwhelmingly emphasizes pharmaceutical and surgical interventions. It's not that your doctor is against you - they're working within the framework they were given. My advice is to lead with data, not confrontation. Bring your lab results. Show the trends. If you've been making lifestyle changes and your numbers are improving, that evidence speaks louder than any argument. Ask questions rather than making declarations: "What do you think about my fasting insulin trending down since I changed my diet?" is more productive than "I've decided I don't need that medication." If your doctor is open-minded and willing to monitor you while you try lifestyle interventions, that's a great partnership. If they're not willing to even consider it, it may be worth seeking a physician who practices functional or metabolic medicine - someone trained to look for root causes rather than just manage symptoms. The relationship with your doctor is important, but ultimately this is your body and your health. The best physicians will support an informed patient.

7. The longevity space is flooded with new supplements, protocols, and clinics every month. What's your personal framework for evaluating a new longevity claim before you'd consider trying it or recommending it?

I apply the same rigor I used for decades evaluating peer-reviewed research. My framework comes down to a few filters. 

First, what's the mechanism? I want to understand how something works at a biological level. If someone can't explain the mechanism and it's just "this makes you feel better," I'm skeptical. 

Second, what's the quality of the evidence? Is it randomized controlled trials in humans, or is it a single mouse study being extrapolated far beyond what the data supports? 

Third, what's the risk-to-benefit ratio? Even promising interventions can carry side effects or interact with other things you're doing. I'm much more conservative about recommending something that carries real downside risk. 

Fourth - and this is the one most people skip - who's funding the research? The longevity industry has enormous financial incentives. When the people selling you a supplement are also funding the studies that support it, that's worth factoring into your evaluation.

Finally, I always ask: does this intervention address a root metabolic mechanism, or is it a band-aid on a downstream symptom? The interventions with the strongest evidence - nutrition, fasting, sleep, exercise, stress management - remain the foundation. Everything else is incremental at best.

8. You've seen metabolic health from both sides - as a professor reviewing the research and as a patient who had to save his own life. What's one intervention you was skeptical of as a scientist but changed your mind on after experiencing the results personally?

Fasting. As a traditionally trained physician, the idea of voluntarily not eating for extended periods seemed counterintuitive and potentially dangerous. Everything I had been taught emphasized regular meals, "balanced" caloric intake, and the importance of not skipping breakfast. When I first looked at the fasting literature, I found the animal data compelling but was cautious about translating it to humans. Then I tried it myself. The clarity of thought, the improvement in biomarkers, and the speed at which my metabolic numbers moved in the right direction were hard to ignore. Fasting insulin dropped. Inflammation markers went down. My energy became more stable, not less. I went from skeptic to advocate, not because of a single study, but because the combination of the evidence and my own experience was undeniable. I've now co-hosted multiple fasting challenges and have seen similar transformations in thousands of participants. The science supports it, and the lived experience confirms it.

9. What concerns you most about how the longevity industry is developing right now, and what would you tell someone who's spending thousands a year on health products to be cautious about?

What concerns me most is the growing gap between what's being marketed and what's actually supported by evidence. The longevity space is attracting enormous amounts of money, and with that comes a flood of products, clinics, and protocols that look scientific on the surface but are often built on thin evidence - a single rodent study, a mechanistic hypothesis that hasn't been tested in humans, or celebrity endorsements masquerading as clinical proof. If you're spending thousands a year, ask yourself honestly: have you nailed the fundamentals first? Because no supplement stack or expensive therapy can outperform a bad diet, poor sleep, and chronic stress. 

The biggest returns come from the least glamorous interventions - cutting out refined carbohydrates and seed oils, getting restorative sleep, managing stress, moving your body, and incorporating time-restricted eating. Those are essentially free.

I'd also be cautious about clinics offering "longevity panels" with dozens of exotic biomarkers and then selling you proprietary supplements to "optimize" them. That's a business model, not medicine. Spend your money on high-quality food, a good physician who understands metabolic health, and periodically run the markers that actually matter — fasting insulin, hsCRP, hemoglobin A1C, lipid panels with particle size. That's where the real signal is.

10. What's one thing you believe about metabolic health or longevity today that you think mainstream medicine will accept within the next decade?

That metabolic dysfunction - specifically insulin resistance and chronic inflammation - is the common root cause connecting most of the chronic diseases we die from: cardiovascular disease, type 2 diabetes, Alzheimer's, many cancers, fatty liver disease, and more. Right now, mainstream medicine treats these as separate diseases with separate specialists and separate drug regimens. Within the next decade, I believe we'll see a paradigm shift toward recognizing them as different manifestations of the same underlying metabolic problem. And with that recognition will come an acceptance that lifestyle interventions - nutrition, fasting, sleep, movement, and stress management - are not "alternative medicine." They are first-line medicine. The evidence is already overwhelming. What's catching up is the institutional will to act on it. When that shift happens, it will fundamentally change how we train physicians, how we structure healthcare, and how we define what it means to treat disease. We'll stop managing symptoms and start addressing causes. That's the future I'm working toward.