Keto vs low‑fat ad libitum trial findings

In this episode, I’m joined by Dr Kevin Hall from the NIH to unpack the science behind ultra-processed foods, energy balance, and the new U.S. Dietary Guidelines.

We explore what controlled feeding studies reveal about why people tend to eat more calories on ultra-processed diets, and whether it’s the foods themselves or the broader environment driving these effects.

What We Cover

• Key takeaways from the new U.S. Dietary Guidelines
• What ultra-processed foods actually mean in research vs policy
• Why people eat more calories without noticing
• The role of energy density and hyper-palatable foods
• Whether ultra-processed foods can be improved rather than eliminated
• Individual variability in response to diet

A fascinating look at the intersection of biology, behaviour, and the modern food system.

You can learn more about Dr Kevin Hall’s work at his website, follow him on X, or connect on LinkedIn. His book, Food Intelligence: The Science of How Food Both Nourishes and Harms Us, co-authored with Julia Belluz, explores the science of metabolism and ultra-processed foods.

• Intro (00:00)
• 2025 Dietary Guidelines First Impressions (01:03)
• Why They Avoided "Ultra-Processed" Language (04:11)
• The UPF Definition Nobody Agrees On (09:59)
• What Actually Makes You Overeat UPFs (19:08)
• Two Food Properties That Hijack Your Calories (27:38)
• What Happens When You Fix Ultra-Processed Food (34:28)
• Why Big Food Won't Fix Its Own Products (45:08)
• How We Went from Famine Fear to Calorie Glut (51:33)
• Why Some People Overeat UPFs and Others Don't (58:12)
• Is Obesity Actually Genetic? (1:01:22)
• Carbs vs. Fat: What the Data Actually Shows (1:06:34)
• Keto vs. Low-Fat: The Metabolic Ward Results (1:17:35)
• A Top Nutrition Scientist's Honest Diet Advice (1:26:22)
• Will Food Labels Actually Change What You Eat? (1:33:11)
• "Am I a Food Industry Shill?" -Kevin Hall (1:41:36)
• Why Kevin Hall Left the NIH for Drug Research (1:44:29)
• The Study He'd Run With Unlimited Funding (1:47:49)

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Simon Hill, MSc, BSc (Hons)

• Creator of theproof.com
• Host of The Proof with Simon Hill
• Author of The Proof is in the Plants

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