The NEW Era of Fasting: PSMF vs Water Fasting & The 3 Types of Hunger | Dr. Jason Fung
Optimal Protein Podcast with Vanessa Spina
Vanessa Spina
4.6 • 795 Ratings
🗓️ 9 March 2026
⏱️ 79 minutes
🧾️ Download transcript
Summary
In this episode, Vanessa is joined by Dr. Jason Fung, author of The Hunger Code, to unpack the hormonal science behind fat loss — and how fasting may be entering a new era.
They start with the three types of hunger and why obesity is not simply about willpower, but disrupted hormonal signaling. We break down insulin's role in fat storage, obesity, and how ultra-processed foods blunt satiety hormones.
Vanessa and Dr. Fung also discuss how protein, fiber, and fat affect hunger very differently than refined carbohydrates — and why a calorie is not metabolically neutral.
Then they shift to fasting. Dr. Fung shares his current protocols and comments on emerging research supporting Protein-Sparing Modified Fasting (PSMF) as a more practical, muscle-conscious alternative to prolonged water fasting.
They cover:
• PSMF vs water fasting
• Protecting lean mass during fat loss
• GLP-1 medications — risks and unintended consequences
• Appetite suppression vs true metabolic health
• Fat loss considerations for women in peri- and post-menopause
This conversation challenges the idea that all fasting approaches are created equal — and reframes modern fat loss through a hormonal lens.
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Transcript
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| 0:00.0 | Welcome to the Optimal Protein Podcast. I'm Vanessa Spina. |
| 0:04.7 | Hello, my friends. Welcome back to the optimal protein podcast. I'm your host, Vanessa, and I am so |
| 0:11.1 | excited for today's episode because we are diving deep into the hormonal science of hunger and |
| 0:17.8 | fat loss with one of the most recognized voices in fasting and metabolic health, |
| 0:23.1 | Dr. Jason Fung. In today's conversation, we explore what may be one of the most important |
| 0:29.5 | shifts in the weight loss discussion. The idea that hunger is not simply a matter of willpower |
| 0:36.1 | or calories, but a hormonally regulated system. |
| 0:40.8 | Dr. Fung breaks down the three distinct types of hunger and explains why understanding them |
| 0:46.9 | completely changes how we approach fat loss. We discuss why a calorie is not just a calorie, how ultra-processed foods blunt are, say, tidy |
| 0:57.5 | hormones, how different macros, protein, fiber, and fat affect insulin and hunger signaling very |
| 1:05.1 | differently than refined foods and carbohydrates. We also get into fasting, but not in the way you may expect. We talk about |
| 1:13.0 | the latest science on the evolution of fasting protocols, emerging research around approaches |
| 1:20.5 | like protein spraying modified fasting days, and why prolonged fasting with water only may not be the most practical or muscle |
| 1:29.8 | preserving strategy for many people. We also have a very important discussion about JLP1 |
| 1:35.4 | medications, including the potential risks and unintended consequences. And we talk about how |
| 1:41.6 | women in Perry and postmenopause can approach fat loss strategically |
| 1:45.9 | in this new hormonal landscape. |
| 1:48.5 | This episode is packed with physiology if you love to geek out on the different roles of |
| 1:53.9 | hormones like insulin, how they affect fat loss and fat storage, as well as all of the satiety |
| 1:59.9 | hormones and also sex hormones. It is also |
| 2:03.5 | packed with practical insight. And I think you're going to walk away thinking differently about |
| 2:08.8 | hunger, hormones, and modern fat loss. Now, I can't wait to get into today's episode with |
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