Podcast Summary: The School of Greatness
Host: Lewis Howes
Guest: Dr. Michael Greger
Episode: How to REVERSE Aging With What You Eat Daily
Date: November 28, 2025

Overview

In this insightful episode, Lewis Howes interviews Dr. Michael Greger, a renowned physician, author, and health advocate, on the science of slowing and potentially reversing the aging process through diet and lifestyle changes. Drawing from his latest book, "How Not to Age," Dr. Greger presents evidence-based strategies for achieving vibrant, healthy longevity—debunking the myth that declining health is inevitable with age. Their conversation covers the impact of diet, exercise, fasting, meal timing, and more, all in Dr. Greger's energetic and positive tone.

Key Discussion Points & Insights

The Power of Diet and Lifestyle in Aging (02:47–07:49)

• Diet is Crucial for Longevity: Dr. Greger emphasizes that while genetics account for about 25% of lifespan differences, lifestyle—especially diet—makes all the difference.
  • “Really only about 25%. Based on studies of identical twins, only about 25% of the difference in lifespan between people is due to genetics.” (02:47)
• Blue Zones as Models: Populations with exceptional longevity (Blue Zones) center their diets around whole plant foods and minimize processed food, meat, dairy, and sugar.
• Diet Now Surpasses Tobacco as #1 Killer in the US: Diet-related diseases have overtaken smoking as the leading cause of preventable death.

The Five Main Keys to Aging Better (05:42–07:49; 19:52–25:58)

1. Diet: Focus on whole, unprocessed plant foods—fruits, vegetables, legumes, whole grains, nuts, and seeds.
2. Smoking Cessation: Avoid all forms of smoking and nicotine addiction, as these dramatically shorten lifespan.
3. Exercise: Even moderate daily physical activity (20 minutes/day) has significant benefits.
4. Maintain Healthy Weight: Avoid obesity through diet and activity.
5. Regular Consumption of Fruits and Vegetables: At least five servings per day.

• “A decade of life is possible just through not smoking, not being obese, exercising even like 20 minutes a day, [and] five servings of fruits and vegetables, really basic stuff.” (08:27)

Fasting & Meal Timing—What Actually Works? (09:38–17:24)

• Fasting & Autophagy: Fasting can boost the body’s cell-cleaning process (autophagy), but significant benefits require two days or more of fasting, which should only be done with medical supervision.
• Intermittent Fasting: Evidence points to “early time-restricted feeding”—eating meals earlier in the day ("skip supper, not breakfast")—as most beneficial for metabolism and longevity.
  • “The exact same food eaten in the morning is less fattening than the exact same food... eaten in the evening.” (12:46)

Key Quote

• “Ideally we should not be eating when it's dark, should not be eating after 7pm. Our bodies just have these exaggerated responses to it.” (12:46)

• Blue Zone Case Study: The Loma Linda Adventist community, notable for skipping dinner or having their largest meal at lunch, is currently the longest-living formally studied population.

• Circadian Rhythm: The body’s daily rhythms strongly influence how it metabolizes food. Disrupting these rhythms (e.g., by eating late or doing shift work with irregular hours) can harm health.

The “Daily Dozen” Checklist for Longevity (19:52–25:25)

• Dr. Greger’s practical framework includes:
  • Daily servings of dark leafy greens and berries
  • Legumes: Beans, split peas, lentils, and chickpeas are the single most important longevity food due to their prebiotic content.
  • Nuts: Especially walnuts for their omega-3 content and proven artery benefits.
  • Whole Grains: Especially intact grains like oat groats and steel-cut oats.
  • Flaxseed and turmeric

Notable Quotes

• “Legumes rule the roost on a per serving basis, but actually on an ounce per ounce basis, nuts are associated with the longest lifespan compared to any other type of food out there.” (25:25)
• “There’s really only one that pulls ahead. That’s walnuts.” (25:47)

Dr. Greger’s Top 5 Foods for Healthy Aging (21:15–25:58)

1. Legumes (beans, lentils, chickpeas)
2. Nuts (especially walnuts)
3. Whole grains (preferably least processed)
4. Dark leafy greens
5. Berries

Salt, Processed Foods, and a Surprising Longevity Hack (28:25–35:21)

• Salt Intake Is a Major Risk: Excess sodium is the single worst dietary factor globally. Most comes from processed foods, not added salt.
• Hack: Replace table salt (sodium chloride) with potassium salt (potassium chloride), which can cut cardiovascular deaths dramatically for those with healthy kidneys.
  • “Just by switching to half potassium salt... they effectively made themselves 10 years younger when it came to the risk of premature death.” (31:59)

Supplements vs. Whole Foods (44:43–49:14)

• Whole foods are superior to isolating nutrients in supplements.
  • “The food form of these nutrients is the best form to get them.” (48:46)
• Fiber: Diverse dietary fibers found in a variety of plant foods (not just a single fiber supplement like psyllium) feed different good gut bacteria.
• Synergy: Compounds in whole foods work together for amplified effects ("one plus one is greater than two" principle, e.g., with pomegranate studies).

Glucose, Vinegar, and Blood Sugar Regulation (52:41–56:34)

• Frequent blood glucose spikes may accelerate aging.
• Dr. Greger recommends two teaspoons of vinegar with every meal to reduce blood sugar spikes and visceral fat, and to activate anti-aging pathways.
  • “You can randomize people to get vinegar... and saw a significant difference in visceral body fat, which is the most dangerous body fat.” (53:13)
• Always dilute vinegar to prevent esophageal damage.

Cellular Aging, Inflammation, and Zombie Cells (62:03–68:47)

• Cellular Senescence: As we age, our body accumulates "zombie" senescent cells that fuel inflammation ("inflammaging"). The immune system’s ability to clear these declines with age.
• Anti-aging Phytochemicals: Three key natural compounds help remove senescent cells:
  1. Fisetin (strawberries)
  2. Quercetin (onions, red onions best; kale; tea; capers)
  3. Piperlongumine (long pepper; a Szechuan-like spice)

Why Doctors Get So Little Nutrition Training (70:21–74:03)

• Most physicians receive minimal nutrition education—only four hours on average in medical school, mostly biochemistry, not practical disease prevention. Dr. Greger’s own inspiration came from his grandmother’s heart disease reversal through diet, and the pioneering Lifestyle Heart Trial by Dr. Dean Ornish.

Social Barriers to Widespread Healthy Behaviors (81:28–86:33)

• Despite scientific consensus (e.g., processed meat is a known human carcinogen), mixed messages in media and profit motivations of the food industry muddy public understanding and slow the adoption of healthy behaviors.

Chronological vs. Biological Age (86:53–91:20)

• Biological age: The functional state of your body, not the years lived. It is modifiable through lifestyle, not fixed by the calendar.

Notable Quotes & Memorable Moments

• On diet vs. genetics:
  “Only about 25% of the difference in lifespan between people is due to genetics.” (02:47, Dr. Greger)

• On power of lifestyle changes:
  “A decade of life is possible just through not smoking, not being obese, exercising even like 20 minutes a day, five servings of fruits and vegetables, really basic stuff.” (08:27, Dr. Greger)

• On meal timing:
  “If you’re going to eat a donut or something, do it in the morning. Actually your body, because of our circadian rhythms, is better able to handle it.” (12:46, Dr. Greger)

• On nuts and longevity:
  “It is one of the only foods, there's only two foods that have ever been associated with increase in literally years, plural, a single food. And nuts is one of them.” (36:15, Dr. Greger)

• On salt substitutes:
  “Just by switching to half potassium salt...they effectively made themselves 10 years younger when it came to the risk of premature death.” (31:59, Dr. Greger)

• On love and meaning:
  “If you can configure your life to not just do what you’re good at... but to do something meaningful for others and to kind of look outside yourself... that would definitely be one of the truths.” (93:14, Dr. Greger)

Timestamps for Key Topics

• 02:47 — Diet’s role in aging and longevity
• 05:42 — Five main lifestyle keys for longevity
• 09:38 — Fasting, autophagy, and meal timing
• 12:46 — Why eating earlier is better for health
• 19:52 — Dr. Greger’s “Daily Dozen” framework
• 21:15 — Top anti-aging foods
• 25:47 — Why walnuts are the best nut
• 31:59 — Salt intake and the potassium salt hack
• 44:43 — Supplements vs. whole foods
• 53:13 — Vinegar, blood sugar, and fat loss
• 62:03 — Cellular senescence & anti-aging compounds
• 70:21 — Medical education & nutrition gaps
• 86:53 — Biological age vs. chronological age
• 93:14 — Dr. Greger’s three truths for life

Conclusion

Dr. Michael Greger makes a compelling, science-backed case that we have meaningful control over how we age through basic, consistent habits: centering our diet on whole plant foods, maintaining healthy weight, exercising, quitting smoking, and paying attention to meal timing and circadian rhythms. He stresses the superiority of whole foods over supplements and advocates for simple fixes like swapping table salt for potassium salt, and adding vinegar to meals. Ultimately, it’s not about chasing miracle pills, but about returning to the basics of healthful living to both lengthen lifespan and improve everyday vitality.

Key Takeaway:
“You have tremendous power over your health destiny and longevity. It’s never too late to start eating healthier.” (02:47, Dr. Greger)

Resources:

• Dr. Greger’s free resources: nutritionfacts.org
• Book: "How Not to Age" by Dr. Michael Greger

Host: Lewis Howes
Guest: Dr. Michael Greger