HoldsUp

Mark Hyman, MD · 2025-06-18 · Andy Galpin, Mark Hyman (host)

The Real Reason You're Always Tired Has Nothing to Do With Sleep

32 claims checked against research: 2 contradicted 1 contradicted online 8 overstated 3 needing context 12 supported 6 unverified

8

Overstated

0:13:10Andy Galpinoverstatedmoderate

Sleep restriction to five hours per night causes the brain to adapt by rapidly increasing the amount and speed of entry into deep sleep and REM cycles.

"and we're going to load you down to five hours of sleep per night. And then we're going to stay at five hours of sleep no matter what... You know what would happen to your deep sleep? It would rocket up. Why? Because your body would learn pattern recognition really quickly. "I don't have eight hours to mess around. I will get into deep, I will get into REM, I will get into these cycles hyper-fast because there's no wiggle room there."" (said at 0:13:10)

Restricting sleep to five hours per night does not cause the absolute amount of deep sleep (slow-wave sleep, SWS) to "rocket up," nor does it increase total REM sleep. Under chronic sleep restriction, homeostatic sleep pressure prioritizes slow-wave sleep such that its absolute duration is largely preserved relative to baseline, leading to an increased relative proportion (percentage) of SWS within the shortened sleep window. However, total REM sleep duration is typically reduced because REM sleep predominates in the later hours of a full night's sleep. Furthermore, faster entry into deeper stages is driven by homeostatic pressure (adenosine accumulation and Process S), not cognitive pattern recognition or biological learning.

0:17:01Andy Galpinoverstatedmoderate

Elevated hematocrit and hemoglobin in physically unfit, non-exercising individuals is a common clinical indicator of sleep apnea.

"Really good example: if you see somebody who doesn't exercise, they're unfit, but you see hematocrit and hemoglobin are really high, really good chance you've got some sort of apnea." (said at 0:17:01)

While obstructive sleep apnea (OSA) can induce mild nocturnal hypoxia leading to slight, measurable increases in hemoglobin and hematocrit, clinically significant erythrocytosis or 'really high' hematocrit is uncommon in OSA. Systematic reviews and meta-analyses show that true secondary polycythemia occurs in only about 2% of OSA patients overall (and roughly 6% of severe OSA cases), with average hematocrit levels remaining well within normal physiological reference ranges. While OSA is considered during the differential diagnosis of unexplained secondary erythrocytosis, markedly elevated hematocrit is not a typical presentation or reliable standalone indicator of sleep apnea.

0:00:27Andy Galpinoverstatedmoderate

Having high-quality skeletal muscle makes it significantly harder to develop metabolic disorders.

"If you have high-quality muscle, it's really hard to have metabolic problems." (said at 0:00:27)

Skeletal muscle is the primary site of insulin-stimulated glucose disposal, and higher muscle quality—characterized by lower inter- and intramuscular fat infiltration (myosteatosis) and higher functional strength per unit of mass—is consistently associated with improved insulin sensitivity and a significantly lower risk of metabolic syndrome and incident type 2 diabetes. Systematic reviews and longitudinal cohorts demonstrate that poor muscle quality (such as higher low-density muscle area and intramuscular lipid accumulation) independently increases the odds and hazard of insulin resistance, metabolic syndrome, and type 2 diabetes by twofold or more. However, phrasing this relationship as making metabolic disorders 'really hard to have' overstates the absolute protective effect, as metabolic diseases are multifactorial and can still develop via hepatic insulin resistance, pancreatic beta-cell dysfunction, genetics, and dietary excess regardless of muscle quality.

0:44:14Andy Galpinoverstatedlow

Specific structures in the brain physically shrink when a person avoids pushing through discomfort and grow larger when they regularly engage in challenging tasks.

"there's specific areas of the brain that are developed when you push through on discomfort. And so there's an actual physical structure that gets smaller when you don't do that very often. It gets larger when you do it more often." (said at 0:44:14)

The speaker is referring to research on the anterior midcingulate cortex (aMCC), a brain region implicated in tenacity, effort-based cost-benefit computation, and the subjective 'will to persevere.' Cross-sectional neuroimaging studies have observed larger or preserved aMCC volume and cortical thickness in groups exhibiting sustained high effort or cognitive maintenance (such as endurance athletes and elderly 'superagers') compared to populations with reduced physical or cognitive engagement. However, claiming as a demonstrated fact that the structure dynamically physically shrinks from avoiding discomfort and grows larger from repeatedly pushing through it overstates the evidence: these observations stem primarily from cross-sectional associations, case reports of direct electrical stimulation, and narrative reviews, rather than prospective longitudinal trials proving bidirectional structural hypertrophy and atrophy in response to discomfort.

1:14:04Andy Galpinoverstatedmoderate

Having high-quality skeletal muscle mass makes the occurrence of type 2 diabetes extraordinarily rare.

"And now even this week, there's other data that got published on type 2 diabetes and muscle mass, effectively showing if you have high-quality muscle mass, it's extraordinarily rare to have type 2 diabetes." (said at 1:14:04)

Higher muscle quality (assessed by functional metrics like handgrip strength per unit of muscle mass, or by lower intramuscular fat infiltration) is associated with a significantly reduced risk of developing type 2 diabetes mellitus (T2DM). For example, a prospective cohort study of 355,209 UK Biobank participants found that individuals in the highest quintile of the muscle quality index had a 64% lower risk of incident T2DM compared to the lowest quintile (HR 0.36, 95% CI 0.34–0.39). However, describing T2DM as 'extraordinarily rare' in individuals with high muscle quality exaggerates the protection, as T2DM is multifactorial and can still develop due to beta-cell dysfunction, visceral adiposity, genetics, and age.

1:21:12Andy Galpinoverstatedmoderate

The greatest amount of AST (aspartate aminotransferase) in the human body is found in skeletal muscle, which frequently leads to elevated serum AST levels in individuals with high muscle mass.

"AST, the most amount of AST in your body is in muscle. So you will always see almost always see elevated AST in people with a lot of muscle mass." (said at 1:21:12)

While skeletal muscle contains a large reservoir of aspartate aminotransferase (AST) due to overall muscle volume, elevated serum AST in muscular individuals (such as weightlifters or bodybuilders) is primarily driven by exercise-induced muscle microtrauma and enzyme leakage rather than baseline muscle mass alone. In healthy individuals, resting AST levels generally remain within standard reference intervals unless strenuous or unaccustomed muscular exertion has occurred within the preceding days.

1:12:23Andy Galpinoverstatedlow

Elevated serum albumin levels (hyperalbuminemia) are almost exclusively caused by acute dehydration and hemoconcentration.

"it's super high in only one case basically: in the case of acute dehydration, right? Because it's a concentration issue, right?" (said at 1:12:23)

While dehydration and hemoconcentration are widely recognized as primary causes of elevated serum albumin concentrations, asserting that hyperalbuminemia occurs "in only one case basically" is overstated. Published clinical literature demonstrates that hyperalbuminemia is frequently observed in clinical settings outside of acute dehydration, including iatrogenic elevation following therapeutic albumin administration in acute and intensive care settings, as well as in stable outpatients associated with metabolic disorders, high BMI, and chronic sympathetic nervous system activation.

1:38:36Andy Galpinoverstatedmoderate

Springbok imaging software uses a 20- to 30-minute full-body MRI scan to create a three-dimensional model and individual volume analysis of every muscle in the body.

"Springbok does the same thing: 20- to 30-minute full MRI, full-body MRI scan, and it gives us a three-dimensional image of every muscle on your body." (said at 1:38:36)

Springbok Analytics uses artificial intelligence to perform rapid three-dimensional segmentation and volumetric analysis of musculature from MRI scans. However, claiming that it provides individual analysis of 'every muscle on your body' is an overstatement. The human body contains over 600 skeletal muscles; published evaluations of whole-body AI muscle segmentation algorithms (including Springbok's pipeline) quantify up to 71 individual muscles across the upper limbs, trunk, and lower limbs, rather than every anatomical muscle.

Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.