Here's the uncomfortable truth that Dr. Rhonda Patrick is willing to say out loud: everything we thought we knew about caloric restriction and lifespan might be only half the story. The core claim in this conversation with Peter Attia is deceptively simple — lowering IGF-1 through dietary restriction may extend lifespan, but it won't necessarily protect your brain. That lemur study is haunting. You can live longer with 30 percent fewer calories, and arrive at the end of that longer life with less brain to enjoy it.
IGF-1 — insulin-like growth factor 1 — is your body's primary anabolic signal. It tells cells to grow, repair, divide. For decades, longevity researchers treated high IGF-1 as a villain. Caloric restriction drops IGF-1. Low IGF-1 animals live longer in controlled studies. Conclusion: suppress IGF-1, live longer. Except the brain doesn't seem to agree with that conclusion.
There's broad agreement that chronic caloric excess is damaging. Nobody is arguing for perpetual overeating. And there's solid consensus that metabolic flexibility — your body's ability to switch between fuel sources — is a genuine marker of health. Ketogenic diets can sharpen that flexibility, and the animal data on cognitive function is genuinely compelling.
But this is where researchers start to diverge. Some longevity scientists hold the caloric restriction line firmly. Others, like Rhonda Patrick here, are increasingly arguing for a periodized approach — phases of restriction alternating with phases of growth. The oscillation matters. Not permanent deprivation, but cycling between states.
And the genetic piece is real. What works metabolically for one person can genuinely harm another. We are not all running the same biochemistry. Rhonda's willingness to say "my beliefs have changed" is not weakness — it's the only honest position a scientist can hold when new data keeps arriving.
Don't pick a dietary religion and never leave it. Instead, think in phases. Periods of restriction — intermittent fasting, lower protein, lower calories — where IGF-1 drops and your cells run cleanup protocols. Then periods of adequate nutrition, quality protein, nutrient-dense food, where IGF-1 rises and your tissues rebuild. The ratio will be individual. But the cycling itself is probably the point.
We do this with temperature every session at Contrast Collective. Cold drops metabolism, contracts vasculature, activates cold-shock proteins. Heat expands vasculature, drives heat-shock proteins, raises growth hormone. Neither state alone gives you the full benefit. The alternation is the therapy. IGF-1 periodization is the same principle applied to diet. Your biology was built for oscillation — feast and fast, growth and restriction, hot and cold. What it was never built for is the permanent steady state we keep trying to impose on it.