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 - flagged

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.

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.

1:20:52contradictedhighRay 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.

1:22:25contradictedhighRay 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.

1:29:03contradictedmoderateRay 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.

1:33:21contradictedmoderateRay 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.

1:51:41overstatedmoderateRay 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.

1:54:25overstatedlowRay 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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