DavidPerlmutterMD · 2025-02-24 · David Perlmutter (host), Jeff Krasno

Yes, Stress Can Be Good: The Health Benefits of Doing Hard Things | Jeff Krasno

30 research-tied claims examined: 1 contradicted 2 overstated 5 context 19 supported 2 corroborated online 1 unverified

Overstated

0:26:26 David Perlmutter (host)overstatedhigh

Between 83% and 86% of American adults are either prediabetic or diabetic.

"When we see that, you know, some 83 to 86% of American adults now is either pre-diabetic or diabetic, it's hard to imagine that we should therefore consider that to be pretty much normal." (said at 0:26:26)

The speaker appears to have conflated overall cardiometabolic unhealthiness (frequently cited as ~88% of American adults not meeting optimal criteria across blood glucose, blood pressure, lipids, and adiposity) with the specific prevalence of prediabetes and diabetes. Based on National Health and Nutrition Examination Survey (NHANES) data, approximately 14% to 16% of US adults have diabetes (diagnosed or undiagnosed) and approximately 30% to 38% have prediabetes, combining for roughly 45% to 50% of US adults, not 83% to 86%.

context: Prevalence of Optimal Metabolic Health in American Adults: National Health and Nutrition E… (Metabolic syndrome and related disorders 2019) · cited 158x in the literature
"Changing from ATP III (Adult Treatment Panel III) guidelines to more recent cut points decreased the proportion of metabolically healthy Americans from 19.9% (95% confidence interval [CI]: 18.3-21.5) to 12.2% (95% CI: 10.9-13.6)." (abstract, results, passage verified)
pubmed full study (doi)
contradicts: Trends in Prevalence of Diabetes, Pre-Diabetes, and Cardiometabolic Risk Factor Control Am… (Diabetes, obesity & metabolism 2026)
"Among 24 230 participants across all survey years, 6773 had pre-diabetes, and 4784 had diabetes (3826 diagnosed/958 undiagnosed). The age-adjusted prevalence of total diabetes was stable across the study period: 14.6% (95% CI 13.0%-16.2%) in 2013-2014 and 16.3% (14.6%-18.0%) in 2021-2023... The age-adjusted prevalence of pre-diabetes increased significantly during the study period from 26.4% (23.7%-29.1%) in 2013-2014 to 30.7% (28.4%-33.0%) in 2021-2023" (abstract, results, passage verified)
pubmed full study (doi)

0:44:29 Jeff Krasnooverstatedlow

Heat exposure and sauna bathing stimulate the production of brain-derived neurotrophic factor (BDNF), promoting neurogenesis and neuroplasticity.

"So there's it appears that there's the production of all these different kinds of proteins, like BDNF is one that I think has been fairly celebrated as brain-derived neurotrophic factor that seems to maintain neurofunction and, you know, as I understand it, even contribute to neurobiogenesis, so neuroplasticity even later in life." (said at 0:44:29)

The claim is overstated. While acute or controlled passive heating interventions (such as repeated warm-water immersion) have been shown in small human trials to modestly increase circulating peripheral BDNF concentrations, evidence demonstrating that sauna bathing or heat therapy directly stimulates human adult neurogenesis or broad neuroplasticity in the brain is preliminary, indirect, or based on mechanistic extrapolations. Furthermore, excessive or prolonged heat stress has been shown in narrative and preclinical models to activate the hypothalamic-pituitary-adrenal axis and suppress BDNF signaling.

context: Effects of heat environments on depressive disorders: Neurogenesis-mediated mechanisms. (Journal of thermal biology 2025) · cited 2x in the literature
"Heat stress may activate the hypothalamic-pituitary-adrenal (HPA) axis, leading to elevated glucocorticoid levels, which in turn cause hippocampal damage, suppress the expression of brain-derived neurotrophic factor (BDNF), impair neurogenesis and synaptic plasticity, and ultimately promote the onset of depression." (abstract, passage verified)
pubmed full study (doi)
supports: Seven days of warm-water immersion enhances resting irisin and BDNF, but not klotho, in ol… (Experimental physiology 2026)
"Repeated warm-water immersion increased resting BDNF by 2.43 ng · mL -1 (95% CI: 0.64-4.23; P = 0.005; 1.73-fold) and irisin by 0.94 ng · mL -1 (95% CI: 0.25-1.63; P = 0.005; 1.65-fold)." (abstract, results, passage verified)
pubmed full study (doi)

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.