HoldsUp

Ray Cronise

Zero Gravity

Ray Cronise is a former NASA material scientist and the co-founder of Zero Gravity, a company that provides weightless parabolic flights to consumers and researchers. His work and discussions focus on healthspan, weight loss, intermittent fasting, and cold thermogenesis.

27 claims checked on air: 1 context 6 contradicted 3 overstated 12 supported 5 unverified 9 flagged

What they said on air

0:06:05contradictedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Alanine levels increase significantly during prolonged fasting because it is primarily utilized for gluconeogenesis.

"Of course, things like alanine, which is mainly used for gluconeogenesis, went through the roof; lipids go through the roof." (said at 0:06:05)

The claim is contradicted by physiological evidence regarding amino acid metabolism during fasting. While alanine is indeed the principal gluconeogenic amino acid extracted by the liver, circulating plasma alanine levels do not increase ("go through the roof") during prolonged fasting; instead, they drop precipitously. Classic metabolic studies in humans show that preferential hepatic uptake of alanine for gluconeogenesis rapidly depletes circulating levels, leading to sustained hypoalaninemia. In contrast, branched-chain amino acids (leucine, isoleucine, valine) and lipid metabolites (free fatty acids and ketone bodies) rise during fasting.

0:09:05overstatedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Essential amino acids such as methionine increase fecundity but are negatively associated with longevity.

"I mean, you guys are in prime reproduction time, so to get fecundity to go up, we want to increase essential amino acids. We know that things like methionine, whatever, increase fecundity. At the same time, where I am, which I'm done with that process at 51, I want to make sure of longevity, and they're also negatively associated with longevity." (said at 0:09:05)

The trade-off between reproduction (fecundity) and lifespan mediated by essential amino acids and methionine is a well-established phenomenon in laboratory model organisms (such as Drosophila melanogaster and rodents), but direct evidence demonstrating that manipulating dietary methionine or essential amino acids modulates fecundity and human longevity is lacking. In model organisms, restricting protein or methionine extends lifespan, whereas supplementing essential amino acids generally enhances reproductive output at the expense of lifespan.

0:11:05unverifiedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

At the turn of the 20th century, the average person spent 60% of their income on food.

"if you think about the average person was spending 60% of their income on food." (said at 0:11:05)

No published record matching the claim that the average person spent 60% of their income on food at the turn of the 20th century was located; this does not prove the claim false.

0:27:50unverifiedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

The respiratory quotient (RQ) for ethanol metabolism is approximately 0.67, for carbohydrates is 1.0, for fats is 0.69 to 0.70, and for amino acids averages 0.84.

"you'll see that, you know, you get a two on one side, three on the other, and you do the two and then three, and you get the respiratory quotient of 0.67... Carbohydrates of all types, doesn't matter what kind they are, all of the glucose, anything that's dropping in there, those have a respiratory quotient about 1. And then fats or lipids all run between 0.69 and 0.7. So what's really interesting is that amino acids, they average 0.84 if I average all of them." (said at 0:27:50)

No published record matching the claim regarding the specific respiratory quotient values for ethanol (0.67), carbohydrates (1.0), fats (0.69–0.70), and amino acids (averaging 0.84) was located; this does not prove the claim false.

0:32:23needs contextmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Mild cold stress naturally lowers the respiratory quotient (RQ), shifting substrate utilization toward fat oxidation.

"it turns out mild cold stress naturally tends to lower your RQ, meaning shifting towards fat." (said at 0:32:23)

Mild cold exposure (above the shivering threshold) can promote lipid utilization and non-shivering thermogenesis mediated by brown adipose tissue and skeletal muscle, and changes in thermoregulatory mediators like irisin correlate with lower respiratory quotient (RQ) and higher fat oxidation. However, whole-body indirect calorimetry studies indicate that this shift is not universal: controlled 24-hour trials of mild cold (e.g., 19 °C) found no significant overall decrease in 24-hour respiratory exchange ratio (RER) across all participants, and cold-induced metabolic flexibility varies considerably by ethnicity and individual metabolic status. Furthermore, if cold stress becomes severe enough to induce shivering, substrate utilization shifts heavily toward carbohydrate oxidation rather than fat oxidation.

0:38:04supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Blending plant foods ruptures cell walls to increase bioavailability and access to cellular nutrients compared to whole plants.

"blending certainly ruptures the cells, certainly get more access." (said at 0:38:04)

Evidence from human trials and in vitro digestion studies demonstrates that intact plant cell walls physically encapsulate intracellular nutrients, limiting the penetration of digestive enzymes and the release (bioaccessibility) of cellular contents. Mechanical disruption, such as blending, milling, or fine processing, ruptures the cell walls, directly increasing the release and bioavailability of intracellular macronutrients and micronutrients compared to intact whole plant tissues.

0:42:10supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Eating starches in the evening results in slower blood glucose clearance and prolonged glucose tailing compared to earlier in the day.

"If you're eating starches in the evening, instead of getting those sharp peaks that you saw today, you'll get tailing. So this is true. I mean, there's no doubt that you'll get tailing. The glucose doesn't clear as fast the later in the evening." (said at 0:42:10)

Human circadian physiology trials consistently demonstrate that carbohydrate and starch consumption in the evening results in reduced glucose tolerance, decreased early-phase insulin secretion, and slower glucose clearance compared to morning consumption. This manifests as sustained postprandial hyperglycemia and prolonged clearance curves ('tailing') rather than the rapid peak and return to baseline typical of earlier meals.

0:47:35supportedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

The longest medically supervised water fast recorded in published literature was 382 days, during which the patient lost 276 pounds and reached 185 pounds while taking only multivitamins and intermittent electrolytes.

"the longest medically supervised water fast was 382 days. HOST: And that—382 days? GUEST1: Yeah, 382. He lost 276 pounds in 382 days. I'll send you the paper. Actually, I might have even posted it up on your thing, but it's 382 days medically supervised. HOST: No supplements or anything? GUEST1: They did a multivitamin and then in the middle, 49 days, they had to do some electrolytes, but other than that it was fine, and he weighed 185 when he was done." (said at 0:47:35)

The speaker accurately describes a famous 1973 single-case report by Stewart and Fleming published in the Postgraduate Medical Journal (PMID 4803438). The report documents a 27-year-old male patient who underwent a medically supervised fast of 382 days, starting at 456 lb (207 kg) and ending at 180 lb (81.6 kg), losing 276 lb. Management included daily multivitamins, vitamin C, potassium supplements when plasma levels dropped, and sodium later in the fast. As this is a single case report describing an extraordinary clinical protocol, the certainty of evidence for general application is very low.

0:51:59unverifiedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Eating food generates NADH, which directly shuts off SIRT1 activation.

"And SIRT1 gets activated every time you're making—so when you're eating anything, you know, when you're eating food you're going to make NADH, which shuts off SIRT1" (said at 0:51:59)

No published record matching the claim that eating food generates NADH which directly shuts off SIRT1 activation was located; this does not prove the claim false.

1:02:33supportedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Chitin found in crab shells is a carbohydrate.

"Chitin in crab shells, carbohydrate." (said at 1:02:33)

Chitin is a long-chain polysaccharide (carbohydrate) composed of repeating β-(1,4)-N-acetyl-D-glucosamine units. It serves as a major structural component in the exoskeletons of crustaceans, including crab and shrimp shells, and is the second most abundant natural polysaccharide after cellulose.

1:03:00supportedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Following the McGovern Report, United States government food policy adopted a pattern of naming specific whole foods when recommending increased intake ('eat more fruits and vegetables') but only naming nutrient categories rather than specific foods when recommending reductions ('eat less saturated fat, eat less oils, eat less refined sugars').

"We have the "eat more, eat less" policy in the United States. It came out after the McGovern Report, which basically is when we're going to say something good about food from a government perspective: eat more fruits, eat more vegetables. If it's something that's bad, we're not allowed to name the food: eat less saturated fat, eat less oils, eat less refined sugars." (said at 1:03:00)

Historical and policy analysis of United States dietary guidelines confirms the speaker's account. When the Senate Select Committee on Nutrition and Human Needs (chaired by Senator George McGovern) released the initial 'Dietary Goals for the United States' in February 1977, it explicitly recommended that Americans 'decrease consumption of meat'. Following fierce opposition from the cattle, egg, and dairy industries, the committee published a revised edition later that year altering the wording to nutrient-based language (e.g., choosing meats that 'reduce saturated fat intake'). Subsequent federal dietary guidance, including the Dietary Guidelines for Americans published jointly by the USDA and HHS, established an enduring precedent of promoting specific foods when encouraging consumption ('eat more fruits and vegetables') while using abstract biochemical or nutrient terms ('reduce saturated fat, sodium, added sugars') to avoid advising against purchasing specific agricultural commodities.

1:03:39contradictedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

When measured as fat per calorie across all different cuts of meat, the fat content is between 25% and 30%, meaning there is no truly lean meat.

"Now if you report the fat per weight, it's the same, but if you report fat per calorie on all the different cuts of meat, we're all between 25–30%. There's no lean meat, they're all about the same, I mean they're very, very close." (said at 1:03:39)

The claim that fat accounts for 25% to 30% of total calories across all cuts of meat—and that there is no truly lean meat—is contradicted by standard nutritional analyses and nutrient data. Fat content and calorie percentage vary significantly across different cuts and species of meat. For instance, skinless chicken breast or turkey breast typically contains around 10% to 20% of total calories from fat (approx. 1–3 grams of fat per 100–165 calories), whereas untrimmed cuts or fatty processed meats can derive 50% or more of their total calories from fat. Furthermore, published analyses of lean meat cuts confirm that specific cuts qualify as lean under USDA standards (containing less than 10 g total fat, 4.5 g saturated fat, and 95 mg cholesterol per 100 g portion). Cuts such as beef tenderloin steak, top sirloin steak, and fresh-lean pork cuts derive a much lower proportion of calories from fat than untrimmed or high-fat cuts, demonstrating a wide variation rather than a uniform 25%–30% ratio.

1:11:12supportedlowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Cold stress and dietary restriction hit the same genes, including UCP1 and PGC-1alpha.

"and what we have in our Metabolic Winter hypothesis paper is the fact that these two traits, cold stress and dietary restriction, hit the same genes, hit the same UCP1, hit the same PGC-1alpha." (said at 1:11:12)

The speaker accurately describes the premise of the 'metabolic winter' hypothesis, which posits that cold stress and dietary/caloric restriction engage overlapping cellular and metabolic pathways. Preclinical and molecular studies confirm that both cold exposure and caloric restriction upregulate shared regulatory programs controlling thermogenesis and mitochondrial biogenesis in adipose tissue, notably uncoupling protein 1 (UCP1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1alpha).

1:20:52contradictedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

In clinically depressed patients, taking five-minute cold showers at 60 degrees Fahrenheit produced results as good as medications for depression.

"But like um on um clinic- clinically depressed patients, they were doing five-minute cold showers with 60 degrees F and and they were having as good as as good of results with medications with their depression." (said at 1:20:52)

The speaker claims that in clinically depressed patients, taking 5-minute cold showers at 60 degrees Fahrenheit produced results as good as antidepressant medications. This is contradicted by the published scientific literature. The original hypothesis proposing adapted cold showers (20°C / ~68°F for 2–3 minutes) as a potential treatment for depression (Shevchuk, 2008) was a theoretical paper published in *Medical Hypotheses* with no clinical trial, no control group, and only informal anecdotal testing in a small number of individuals who did not meet diagnostic criteria for depression. No clinical trial has shown that cold showers perform as well as antidepressant medications in clinically depressed patients.

1:22:00unverifiedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Mild cold stress begins at 80 degrees Fahrenheit in water and 60 degrees Fahrenheit in air, which is where metabolic and hormonal responses start to occur.

"mild cold stress begins at 80 F in water, okay? And it's uh it begins at 60 F in air. So that's about where the that's where you start seeing a change. You start seeing a metabolic response, you start seeing a hormonal hormonal response um at about those temperatures." (said at 1:22:00)

No published record matching the specific thresholds of 80°F in water and 60°F in air as the starting points for mild cold stress, metabolic changes, and hormonal responses was located; this does not prove the claim false.

1:22:25contradictedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Non-shivering thermogenesis can produce a 300% to 500% increase in metabolic rate.

"and you go into your non-shivering thermogenesis. And yes, you boost up, you can get 300 to 500% increase in metabolic rate, and you can measure this" (said at 1:22:25)

In adult humans, cold-induced non-shivering thermogenesis (primarily mediated by brown adipose tissue activation and futile cycling in muscle) typically increases resting metabolic rate by approximately 10% to 30% above baseline. Increases of 300% to 500% (a 4- to 6-fold increase) can occur during intense muscular exercise or maximal shivering, or in small rodents during rewarming from torpor, but exceed the physiological capacity of human non-shivering thermogenesis by more than an order of magnitude.

1:24:18supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

When a person experiences a muscle pump in the gym, the volume increase is due to added fluid rather than newly added protein or amino acids.

"So like, for example, when you pump up in a gym, you're not adding protein or any amino acids, you're just adding fluid." (said at 1:24:18)

The claim is supported. Acute exercise-induced muscle swelling—commonly referred to as a "muscle pump" or transient hypertrophy—is driven by hyperemia and acute fluid shifts from the plasma into intracellular and extracellular muscle compartments during and immediately after exercise, rather than by acute accretion of new protein or amino acids.

1:28:20unverifiedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

In a cold immersion test with journalist Steven Leckart in 70-degree Fahrenheit water, his respiratory quotient shifted from 1.0 (glycogen burning) to nearly 0.7 (predominantly fat burning), and fat oxidation remained elevated for over an hour after exiting the water.

"And his respiratory quotient went from 1.0, which is most activities are burning glycogen, almost to 0.7, almost pure fat. And for over an hour, he was still burning fat." (said at 1:28:20)

No published record matching the claim of a cold immersion test in journalist Steven Leckart showing a respiratory quotient shift from 1.0 to 0.7 and sustained fat oxidation for over an hour post-exposure was located; this does not prove the claim false.

1:29:03contradictedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Shivering burns carbohydrate as fuel rather than fat.

"And if you're shivering, you're burning carbohydrate, you're not burning fat, right? Shivering is exercise." (said at 1:29:03)

The claim that shivering burns carbohydrate rather than fat is contradicted by human physiological studies. During cold-induced shivering thermogenesis, both lipids (fats) and carbohydrates are oxidized to produce heat. In low- to moderate-intensity shivering, lipid oxidation increases substantially and accounts for approximately 50% of total heat production, with muscle glycogen, plasma glucose, and protein supplying the remainder. While the proportional reliance on carbohydrate (specifically muscle glycogen) rises at higher shivering intensities, fat oxidation remains a significant contributor to energy expenditure during cold exposure.

1:29:24supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Exercise stimulates the production of irisin, which upregulates and creates more brown adipose tissue.

"they start to exercise, they produce irisin. Irisin is known to upregulate and create more brown adipose tissue, and we've seen this happen." (said at 1:29:24)

Exercise stimulates skeletal muscle to express PGC-1α and cleave the membrane protein FNDC5 into the circulating myokine irisin. In preclinical models and cellular studies, irisin directly stimulates the browning of white adipose tissue—upregulating uncoupling protein 1 (UCP1) and thermogenic gene expression to create brown-fat-like (beige) adipocytes. Systematic reviews and meta-analyses in humans also show that both acute and chronic exercise modalities elevate circulating irisin levels.

1:30:22supportedhighRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

In non-shivering thermogenesis, UCP1 causes proton-electron leaks through the mitochondria to produce 100% heat without generating ATP, utilizing lipids as the fuel source.

"non-shivering thermogenesis kicks in, upregulation happens, UCP1, now I'm just using, you know, proton-electron leaks through the mitochondria, and suddenly I'm not producing ATP, I'm just producing 100% heat. What's the cell using to do that? It's it's grabbing the most energy-dense fuel and is using lipids to do it." (said at 1:30:22)

The core mechanism described by the speaker is well established in mitochondrial bioenergetics. Uncoupling protein 1 (UCP1), located in the inner mitochondrial membrane of brown adipose tissue, facilitates non-shivering thermogenesis. UCP1 is activated by free fatty acids (lipids) and catalyzes a regulated proton leak back across the inner mitochondrial membrane. This uncouples nutrient oxidation from the F0F1-ATP synthase, dissipating the electrochemical proton gradient directly as heat rather than storing it as ATP. While the speaker casually mentions 'proton-electron leaks', UCP1 specifically transports protons (H+) across the membrane.

1:33:21contradictedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Bernarr Macfadden was the first to link diet and exercise primarily through the calorie between 1900 and 1911.

"because this all got started around 1911. Well, between 1900, 1911, McFadden was the first one. I'll show you the books in the room where all this got together, and the link of diet and exercise happened primarily through the calorie." (said at 1:33:21)

Historical scholarship on nutritional science and physical culture contradicts the claim that Bernarr Macfadden was the first to link diet and exercise primarily through the calorie between 1900 and 1911. The scientific quantification of human energy balance and dietary calories was established earlier in the late 19th century by nutritional scientists such as Wilbur Olin Atwater, while the popularization of calorie counting for weight management emerged primarily in the late 1910s and 1920s through figures like Dr. Lulu Hunt Peters (author of the 1918 bestseller 'Diet & Health: With Key to the Calories'). While Macfadden was a prominent physical culture entrepreneur during the early 1900s who emphasized exercise and nutrition, his dietary philosophies focused on fasting, whole foods, and natural vitality rather than pioneering calorie-based energy accounting.

1:33:51supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Physical exercise stimulates the production of irisin, which causes tissue to burn fuel and generate waste heat.

"It doesn't make sense for the body to create irisin that creates a tissue that burns fuel and just creates waste heat unless it had unless it was more energetically—to do it, it was more energetically to get up and move to create the waste heat to go get something, that would have probably been the pathway." (said at 1:33:51)

Published literature supports the claim that physical exercise induces the secretion of irisin, an exercise-induced myokine that promotes the browning of white adipose tissue and upregulates uncoupling protein 1 (UCP1), leading to increased thermogenesis and energy expenditure. Seminal research demonstrated that exercise stimulates PGC-1α expression in muscle, triggering the cleavage and secretion of irisin, which drives brown-fat-like phenotypic changes in adipose tissue and elevates energy expenditure. Systematic reviews and meta-analyses in humans confirm that exercise protocols significantly increase circulating irisin levels.

1:42:15supportedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Combining cold stress with a calorie-restricted diet shifts the respiratory quotient (RQ) toward 0.7, indicating a shift toward fat oxidation.

"It definitely shifts your RQ, and what I have seen is that, generally speaking, after a few weeks of cold stress and doing a restrictive diet where you're just running at a chronic deficit, you're going to see your RQ shift more towards 0.7. It lowers, it goes more towards fat burning." (said at 1:42:15)

The speaker's statement accurately reflects well-established metabolic physiology. The respiratory quotient (RQ) represents the ratio of carbon dioxide produced to oxygen consumed: pure carbohydrate oxidation yields an RQ of approximately 1.0, whereas pure fat oxidation yields an RQ of approximately 0.70 to 0.71. Both caloric restriction (fasting/energy deficit) and cold exposure increase reliance on lipid metabolism and thermogenesis, thereby lowering the RQ toward ~0.7.

1:51:41overstatedmoderateRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Pineal gland melatonin secretion begins to decline precipitously around age 40.

"and I'm getting old—obviously past 40, my melatonin is falling off precipitously at this point, you know, that's what all the studies say." (said at 1:51:41)

Melatonin production and nighttime peak amplitudes do decrease with age across the human lifespan, but the literature shows that this decline is gradual or occurs much earlier in life (during childhood and young adulthood before age 30), rather than a "precipitous" cliff starting around age 40. A comprehensive review and analysis of urinary metabolite (6-sulfatoxymelatonin) and plasma melatonin data found that age-related declines occur primarily between childhood and ages 20–30, with little significant difference among groups beyond age 35. While some studies show reduced nocturnal salivary melatonin amplitude in middle-aged adults compared to young adults, the characterization that melatonin levels "fall off precipitously" beginning specifically around age 40 overstates both the rate of change and its onset timing.

1:51:41supportedvery lowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Research shows a synergistic activation effect between melatonin, resveratrol, and SIRT1.

"which is basically SIRT1 and melatonin and resveratrol all working together, so they found a synergistic effect with melatonin and SIRT1, melatonin and resveratrol and SIRT1." (said at 1:51:41)

Preclinical studies have investigated the combined application of melatonin and resveratrol on sirtuin 1 (SIRT1) expression. In animal and in vitro models, combining melatonin and resveratrol demonstrated synergistic effects on enhancing SIRT1 expression and activating downstream pathways (such as the SIRT1/FOXO3a/BCL2 signaling axis) compared to single-agent treatments. However, evidence remains limited to preclinical experimental models, with no clinical trial data in humans.

1:54:25overstatedlowRay Cronise on Cold Thermogenesis, Intermittent Fasting, Wei

Studies from the 1930s showed Australian Aborigines were able to achieve normal REM sleep in sub-freezing (30-degree) conditions without blankets, while Caucasian controls were unable to adapt.

"Now, these are like the Aboriginal studies that were done, these are I think in the '30s or whatever, where they took little refrigerated trucks into Australia, took the natives who, by culture, they sleep under 30-degree temperature, no covers, no blankets. They shiver all night and they get perfect REM sleep. And yet the Caucasian control, those guys were just miserable and they were horrible." (said at 1:54:25)

Classics studies led by Per Scholander and colleagues in the 1950s investigated cold adaptation in Central Australian Aborigines sleeping exposed to near-freezing or cold ambient temperatures (often around 0°C to 5°C). The research demonstrated that Central Australian Aborigines exhibited an insulative-hypothermic type of cold adaptation: compared to white European controls, Aboriginal participants fell asleep without shivering, allowing their body temperature (and metabolic rate) to drop slightly while maintaining uninterrupted sleep. In contrast, unacclimated Caucasian control subjects shivered intensely, reported severe discomfort, and were unable to sleep restfully. However, the speaker overstates and mischaracterizes key aspects of these studies: the classic field research was conducted primarily in the late 1950s (not the 1930s), used custom field tents/equipment (not refrigerated trucks), and did not measure or document 'perfect REM sleep' (electroencephalography and REM sleep stages were not recorded in these field studies; sleep was evaluated via physiological tolerance, skin and core temperature recordings, and metabolic monitoring).

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