Cold Therapy & Weight-Loss Expert Ray Cronise: The Optimal Diet, and Is Exercise Unnecessary?

From his appearance in The 4-Hour Body to an ABC Nightline interview to his TEDMED talk, Ray Cronise is making waves in the nutrition and weight-loss worlds.

Ray is the guy whose ideas led to what in many people’s eyes was the most memorable part of Tim Ferriss’ epic fitness bestseller The 4-Hour Body — that cold stress, in the form of cold showers, ice baths, and cold packs, can play a significant role in aiding rapid fat loss.

Back in 2008, when it was reported that swimmer Michael Phelps ate 12,000 calories a day, it was Ray who noticed that something was amiss. Phelps might have trained harder than anyone, but he wasn’t doing the 10 hours of continuous butterfly per day that under the traditional “calories in / calories out” model would have been necessary to avoid weight gain, when so many calories were coming in.

The missing part of the equation? That the pool was cold, and Phelps’s body had to expend an enormous amount of energy just to keep itself warm.

So Ray, a former NASA scientist who himself had put on some extra pounds over the years, used his scientific training to dive headlong into the study of nutrition and health — and in the process, lost 50 pounds.

And as it turns out, the diet Ray chooses — the one he believes is optimal for weight loss in the short term, health and longevity in the long term — is 100 percent plant-based.

Like any good scientist, Ray is skeptic; indeed, his mindset of questioning long-held assumptions and dogma is what’s primarily responsible for his history of disruptiveness wherever he turns his attention.

But (warning!) this approach means that when you listen to Ray, you’ll likely hear a few things you don’t want to hear: along with his belief that some beloved health foods aren’t so healthy, Ray has recently begun to question whether exercise is really necessary — for weight loss or even long-term health.

In this interview, Ray and I talk for well over an hour to dive deep into his understanding of nutrition and health. He’s not afraid to stand apart from the crowd, and if you listen with an open mind, I promise you’ll learn something new and foundation-shaking.

Here’s what Ray and I talk about in this episode:

  • Ray’s background of disruptiveness with NASA and Zero-G
  • The role cold stress plays in weight loss
  • How Ray got started with a plant-based diet
  • What Paleos and vegans have in common
  • Why it’s utterly ridiculous to label foods as proteins, carbohydrates, and fats
  • Should we avoid added oil and salt altogether?
  • The optimal diet for health
  • Do we really need to exercise at all?

Click the button below to listen now:


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  1. Catherine Anthony says:

    Are there transcripts for the deaf&jard of hearing community?? It would be greatly appreciated!!

  2. Hi Matt!

    I’ve really been enjoying listening to your podcasts during my long runs on Sundays and am really looking forward to listening to this one tomorrow. I always learn a lot from the podcasts and this one promises to be very educational.

    I am also really looking forward to the guest you mentioned will be part of a podcast around New Year’s, she really inspires me and I can’t wait to hear her talk about her HUGE goal!

    Have a great holiday with your family,

  3. I love your posts and look forward to listening to Cronise’s podcast. Yet more and more I wonder about this “perfect” diet. I’m vegan, yes, but I’m certainly not dogmatic about it. If something looks good and I’m hungry for it, I eat it (unless it’s meat, of course). I’ve never been overweight, never even close. I’m a runner and a swimmer and I exercise for the love of movement, and the glorious feeling of sweat. Plus, there’s nothing better than running through the mountains during the Alaska twilight.
    I make smart choices, I want to live a long a healthy life, yes, but this is the only life I have in this form and if I want to eat a bowl of pretzels or a cookie, damn it, I’m going to eat it. And I’m going to savor it, too.
    P.S. Phelps never consumed 12,000 calories a day. In a USA Today interview he was quoted as saying: “I never ate that much. It’s all a myth. I’ve never eaten that many calories.”
    P.S. S. I live in Alaska. It was 19 below zero earlier this week. Cold therapy isn’t something that appeals to me. I’d rather lounge in a hot bath reading novels, thank you very much.

    • Cinthia,

      I agree with you. I too am not a “vegan” as Matt clearly points out. I do empathize and support anyone that takes the ethical approach, but my motivation is different. I grew up with a cattle farm, hunted, etc… I just don’t take that approach, nor is it persuasive. I eat animal products only very rarely. I avoid dairy more than any other single item. As well, simple sugars, highly refined grains, and oils (yes, even olive oil) are only used sparingly. I don’t juice (keep the sugar water and throw out the fiber).

      As for phelps caloric intake, I spoke to him directly and also did a lot of research into confirmed reports of diet. It likely ranged between 8000-10,000, but it was FAR MORE than exercise alone would account. My most recent two blog posts will demonstrate how ineffective exercise is at burning fat (with the exception of extreme endurance athletes like matt).

      There are many other factors that add in on this, but before you go to extremes of alaska, realise what I recommend, mild cold stress, begins at water temperatures of 80F (competitive water temp ranges). All of the recommendations in 4HB were Tim’s work, not mine. I don’t recommend ice baths or cold packs. What I do recommend is that you acclimate to cooler temperatures. For water, the perfect range is 65-75F after acclimation.. In air most people are okay dressed normally at 55-60F. Absolutely do not experiment in water temps below 60F or air below 32F.

      We are all capable of acclimating comfortably to a much wider range and paradoxically the more you acclimate to cooler (I didn’t say cold) temperatures, the better you tolerate warmer temperatures. This process impacts the very genes involved in longevity, sirtuins.

      My goal over the last 2 years was to understand the complete thermodynamics of the human body: you can’t out exercise your mouth and the only species obese and chronically ill are humans and the pets they keep warm and fed; they get the same diseases. In the “real” world calories are scarce. Today, Winter Never Comes.

      brrrr.. alaska LOL.


  4. Really enjoyed this interview. Thanks Matt and Ray!

  5. Very interesting information, I’m glad I stumbled upon this post. Ray’s information is very interesting and I look forward to learning more from his blog and hearing more from him in the future.

  6. I suppose that when the majority believe something is true, it usually isn’t. I still think exercise is necessary for best health. I will be very interested to listen to the podcast to learn more about what Ray says, when I get a bit of time. One thing I don’t agree with is the calories in/out formula. Not all calories are made equal (and extra carbohydrates can more easily than fat be burned as dietary thermogenesis), plus everyone’s metabolism is different.

  7. My experience is completely the opposite in one way from Ray. My experience is that I could not out diet a completely sedentary lifestyle, in other word eat fewer calories than I was burning, if I wasn’t burning that many. For years, I was overweight and I tried to diet off the weight. Eating very little is not very sustainable. I also found that eating very little slowed my metabolism down considerably so that I would stop losing weight. I had found when I was younger that I could lose weight whenever I was on the swim team no matter *how much I ate* very diametrically the opposite of what Ray claims. But I was also swimming about 3 hours a day at that time. I started running and thought that I could burn just as many calories as swimming doing only about 30 minutes a day. Soon, I found out that I could not lose weight eating anything I wanted by running. So, as the years went by, I tried dieting and dieting and dieting my weight off, thinking that weight loss was all about dieting. I really could only lose so much weight by doing this and any weight lost was easily regained. I found in my forties that I practically could not eat anything to lose weight and eating very little slowed down my metabolism. My doctor suggested really exercising a lot more- about an hour everyday. I started bicycling to work everyday and the weight really came off very easily. I never thought that I could eat anything I wanted by exercising- I actually thought I had to eat nothing and exercise all the time to lose weight. So maybe, it wouldn’t have helped if I thought I could eat “anything, in any quantity.” I also started counting calories and found that I lost weight rather quickly consuming 2000 calories a day. I was in a HIV vaccine study at that time and was weighed on a regular basis and the nurse suggested that I increase my calories intake to 2500 as she noted a rapid weight loss. She tended to believe weight should be lost slowly to be lasting. I know of even men who don’t exercise who have to eat only about 1000-1500 calories a day to lose weight. I found I could lose weight eating up to 3000 calories a day. I started eating up to 3000 calories a day and got down the lowest weight that I have been since early college (155 at 6 foot) and I now consume about 3300 calories and maintain this weight. My highest weight ever was 255. I have maintained every single pound of this weight loss for 3.5 years, largely by continuing to exercise as well as counting calories. Since losing the weight, I have transitioned to a plant based diet, esp. by Joel Fuhrman and Michael Greger mainly to solidify my health and weight loss. I think the fallacy of your thinking is to say exercise doesn’t help because a person can’t lose weight by exercise if they continue to consume 9000 calories a day. However, very few people who exercise on a regular basis would have to consume only 1000 calories a day in order to lose weight, as many persons who take the just diet approach would have to do. Being able to consume more calories and still lose weight enables a person to get better nutrition in their diets- although a person has to make sure their calories contain nutrition. Many low calorie diets necessitated by taking a no exercise approach to weight loss are nutrient deficient- it is hard to get enough protein on a plant based diet on 1000 calories a day. Also, many persons who take the plant based diet, no exercise approach to weight loss don’t increase their HDL cholesterol. My HDL was below 20 when I was obese, but now through exercise, it is 77. People can eat *more* calories and still lose weight if they exercise a lot; just because it is not *infinitely more* does not prove that exercise is of no value for weight loss.

  8. Hey, folks. I’m another NASA scientist and follower of Ray Cronise, and I’ve developed an ice vest that promotes mild cold exposure and weight loss. We’ve had an article about us in The Atlantic:

    And a TV interview by an Ozzy news program:

    Here’s our website:

    Also… Matt… I’d be happy to be interviewed by you. 🙂

    – Wayne

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