The Real Reason Every Diet Has Failed You | Dr. Mindy Pelz

22 May 2026 · 7 min · 3 chapters

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In short

Why diets fail, arguing the missing piece is timing of meals and recovery via fasting, not just food choice.

Guest

Dr. Mindy Pelz, who teaches fasting and metabolic health; Lewis Howes hosts The Daily Motivation Show.

Key claims

Humans have two energy systems—after ~8–10 hours without food, the ketogenic/fat-burning system activates, raising ketones that reduce hunger, increase GABA (calm), and improve mental clarity/energy. Constant eating prevents this switch, accelerates aging, and leads to weight gain even with “right” foods because there’s no recovery.

Notable examples

Compares fasting training to marathon training—skipping training causes illness; similarly, jumping into fasting too hard fails. Advice: start around 12 hours fasting, then gradually lengthen; “eat when it’s light out” since nighttime melatonin increases insulin resistance, making late meals store more as fat.

Written by AI. May contain mistakes. Listen to the episode to check what was said.

Chapters

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Understanding Fasting and Energy Systems

0:33 to 2:15

Discover how fasting impacts energy systems and weight loss.

“This is where you get your libido wrong.”

Training Your Body to Fast

2:16 to 4:50

Learn the gradual process of adapting your body to fasting.

“If you're not taking at least eight hours of rest, if you're just constantly eating every hour, right?”

Timing Your Meals for Optimal Health

4:51 to 5:38

Understand the best times to eat for metabolic health.

“Because some people wake up and they want to eat right away, but they say, I can skip dinner.”
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Transcript

Automatic transcript. May contain errors.

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0:32This is where every diet has ever failed. This is where aging starts to speed up. This is where you get your libido wrong. It's because every conversation around nutrition has only been around what we should eat. And what fasting is doing is I'm now, and me plus many other experts are coming to the masses saying, why don't we talk about when we eat? We have two energy systems. One where we create energy when we eat and one energy system that kicks in when we're not eating. So when your blood sugar starts to come down, usually around 8 hours, 8-10 hours without food, you switch over into what we call the ketogenic energy system.

1:13It's also, I like to call it the fat burning system because it's there that your body burns fat for energy. We're like a hybrid car. And so you switch over, you start burning fat for energy. You make something called a ketone. Ketone goes up into the brain. It shuts off hunger. It amps up GABA so you get a lot calmer. And it gives you incredible mental clarity and insane energy. If you never go eight to 10 hours without eating, you will never tap into this system. And so you never get that limitless feeling that we're all getting from fasting. And so if all you're doing is working with the one energy system, you are absolutely accelerating the aging process.

1:58Really? And every diet's going to fail you because what ends up happening is you're only focused on food. And that's why we're hopping from diet to diet to diet. You know, this is great. Then this is great. Then this is great. So you could eat all the right foods. But if you're eating it too frequently, you're still going to gain weight. You could potentially still gain weight. If you're not taking at least eight hours of rest, if you're just constantly eating every hour, right? Or every few hours constantly eating. You could gain a lot of fat. So think of it like exercise. What would happen if you just kept working out and working out and working out?

2:32Every day was like a hard workout, a hard workout. There's no recovery. It's the same thing with fasting. You're giving your body a chance to recover. And the longer you let it recover, the more healing switches turn on. And that's why it slows down aging. And you're burning fat in the process. It's the recovery that matters. Wow. So if you're, but when I go a long time without eating, I feel really hungry. Yeah. And sometimes I feel sluggish or tired at the same time. So when is it that we get this unlimited feeling or this burst of extra energy? When does that happen after extending the window of not eating?

3:10Yeah. So the first thing is it's a training process. So it's just like, you know, if you're going to run a marathon, you don't just throw on some shoes and go 13 miles. You're going to feel pretty bad. I did that before. And I got the flu right afterwards. I ran a marathon without training. Well, maybe it was like three weeks of three miles at a time training. Yeah. But it really wasn't training. Yeah. And I was sick for days and I couldn't walk and I had the flu and it was just like miserable. I finished it, but my body said that was a big mistake. That's right. Yeah. And I paid the price later.

3:40Yeah. And that's the same thing that happens with fasting is that people go, oh, fasting is not for me. It didn't work for me. OK, well, I could say that, you know, that about a training that I didn't properly train for. So what we've got to do is start to slowly work people into this fasted state. And usually I tell people you want to get pretty much to like 12 hours in the beginning. Can you go 12 hours every day? And then you might suffer a little bit. But check this out. In the suffering, your body's healing. So it's called a hormetic stress. You're pushing your body just with enough stress that you're forcing it to repair itself.

4:19It's the same thing you do every time you go into the gym. You're stressing your body so the body repairs itself and makes itself stronger. So when you go into this fasted state, around 12 hours, the body's repairing. Now, what I tell people is if you're suffering at 12, switch back to food and then go again next day. Maybe go another 12, another 13 maybe. And then when that gets easy, you start compressing your eating window more and more, leaving longer time for fasting. So you just didn't train yourself. Right. And is it better to fast in the morning or at night? Because some people wake up and they want to eat right away, but they say, I can skip dinner.

4:57Yeah. And some people say, well, you've got to skip breakfast and then you can eat a little later. Yeah. Have you seen the data on skipping breakfast versus skipping dinner and the benefits for fasting? Yeah, this is hugely debated in the fasting world. Yeah. So I'm just going to give an easy principle that everybody can grab onto. Eat when it's light out. When it's light out, you don't have melatonin in your system. The minute it goes dark, we get melatonin because we're trying to prepare for sleep. So when melatonin goes up, you're more insulin resistant. So the meal you eat at eight o 'clock at night is going to be stored more as fat than if you have it at five in the afternoon.

5:38Why is it so comforting to eat at night, though? I know. It just is like a little late night snack, you know, an extra bowl of cereal for some reason. You just trained yourself. I trained myself, right? Yeah.

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6:34Thank you so much for listening to today's episode of The Daily Motivation, and I hope you have an amazing rest of your day. If you enjoyed this episode, make sure to click the link in the description. That will take you to the full episode of our main podcast on the School of Greatness. And if you are loving the daily motivation, please follow us over on Apple Podcasts and Spotify and leave us a review over on Apple Podcasts right now. And if you want more exclusive content and ad-free listening experience, make sure to subscribe to our Greatness Plus channel on Apple Podcasts right now. And if you want to get even more inspiration from our world-class guests and learn how to improve your life and take it to the next level, then make sure to sign up for the Greatness newsletter and get it delivered right to your inbox over at greatness.com slash newsletter.

7:24Again, have an amazing day, and I'll see you tomorrow with another episode of the Daily Motivation Show.

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From the publisher

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Check out the full episode: https://greatness.lnk.to/1928DM

Most people have spent years obsessing over what to eat. Dr. Mindy Pelz says that's exactly the wrong question.

Your body runs two energy systems. One runs on food. The other only kicks in after 8 to 10 hours without eating. That's the fat-burning, brain-sharpening, hunger-suppressing system. Most people never get there.

That's why diets keep failing. You're only working with half the machine.

Mindy breaks down how to train into fasting gradually. Trying to jump straight to long fasts is like running a marathon with three weeks of 3-mile runs. Lewis learned that the hard way. She also gives one dead-simple rule for timing meals: eat when it's light out. Once darkness hits and melatonin rises, your body stores what you eat as fat.

The suffering at hour 12? That's your body repairing itself. That's the point.

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