7 Needs context
On average, men tend to have a larger amygdala than women.
"I think about some of the imaging data again and the differences between the male and the female brain, and I know that on average men tend to have a larger amygdala." (said at 0:15:44)
In absolute (uncorrected) volume, men on average have an amygdala approximately 10% larger than women. However, meta-analytic evidence shows that this difference is fully accounted for by overall differences in total brain volume and intracranial volume (which are roughly 11% to 12% larger in men). When amygdala volume is adjusted or normalized for total brain size, the difference between sexes becomes small (<1% to 2.5%) and statistically non-significant, indicating that the amygdala is not selectively or disproportionately enlarged in men.
- context: Meta-analysis reveals a lack of sexual dimorphism in human amygdala volume. (NeuroImage 2017) · cited 137x in the literature
"We found that uncorrected amygdala volume is about 10% larger in males, with pooled sex difference effect sizes of g=0.581 for right amygdala (κ=28, n=2022), 0.666 for left amygdala (κ=28, n=2006), and 0.876 for bilateral amygdala (κ=16, n=1585) volumes (all p values < 0.001). However, this difference is comparable to the sex differences in intracranial volume (ICV; g=1.186, p<.001, 11.9% larger in males, κ=11) and total brain volume (TBV; g=1.278, p<0.001, 11.5% larger in males, κ=15) reported in subsets of the same studies, suggesting the sex difference in AV is a product of larger brain size in males. Among studies reporting AVs normalized for ICV or TBV, sex difference effect sizes were small and not statistically significant" (abstract, results, passage verified)
pubmedfull study (doi)
Approximately 20% of women in perimenopause show no cerebral metabolic decline on brain imaging, resembling men through the same period.
"And—and what I think is exciting is that she's also found that 20% of women in perimenopause have no change at all. They look more like men who have no change through the same time period." (said at 0:19:35)
Published multimodality brain imaging studies by Dr. Lisa Mosconi and colleagues confirm the speaker's broader point: age-matched men maintain stable cerebral glucose metabolism during midlife, whereas women undergoing the perimenopausal and postmenopausal transitions exhibit significant reductions in brain glucose metabolism (CMRglc) and mitochondrial bioenergetics on FDG-PET imaging compared to premenopausal controls and men. However, peer-reviewed publications from this cohort report group-level declines in metabolic activity (often showing an average 15–25% reduction in brain energy in affected regions), rather than establishing a specific published metric that exactly 20% of perimenopausal women experience zero metabolic change.
- context: Sex differences in Alzheimer risk: Brain imaging of endocrine vs chronologic aging. (Neurology 2017) · cited 322x in the literature
"Compared to CNT women and to men, and controlling for age, PERI and MENO groups exhibited increased indicators of AD endophenotype, including hypometabolism, increased Aβ deposition, and reduced gray and white matter volumes in AD-vulnerable regions ( p < 0.001)." (abstract, results, passage verified)
pubmedfull study (doi) - context: Increased Alzheimer's risk during the menopause transition: A 3-year longitudinal brain im… (PloS one 2018) · cited 240x in the literature
"Adjusting for age, APOE4 status, and vascular risk confounds, the MENO and PERI groups exhibited higher rates of CMRglc decline as compared to males (p ≤ .015)." (abstract, results, passage verified)
pubmedfull study (doi)
Women diagnosed with PCOS show a 10% to 14% reduction in cerebral glucose utilization.
"and also importantly women diagnosed with PCOS, who have anywhere from a 10% to 14% percent decline in their cerebral utilization of glucose." (said at 0:23:38)
The claimed 10% to 14% reduction is drawn directly from a small pilot study (7 young, normal-weight women with PCOS and 11 controls) using 18F-FDG PET imaging. The study found a 9% to 14% reduction in the cerebral metabolic rate of glucose (CMRglu) in specific brain regions (areas of the frontal, parietal, and temporal cortices), rather than a global whole-brain reduction. Because the evidence comes from a single preliminary study with a very small sample size, broader generalization requires qualification.
Eighty percent of women with polycystic ovary syndrome (PCOS) have insulin resistance.
"80% of women with PCOS have insulin resistance and are put on metformin for that reason and others along with their obesity." (said at 0:24:48)
Estimates of insulin resistance (IR) in polycystic ovary syndrome (PCOS) generally range between 55% and 80% overall, depending on the diagnostic method and population. Gold-standard hyperinsulinemic-euglycemic clamp studies show that approximately 70% to 75% of women with PCOS have IR overall (and 80% to 94% among those with overweight or obesity, compared to 55% to 60% among lean individuals). Meta-analyses also confirm a significant intrinsic reduction in insulin sensitivity (~27%) across all PCOS phenotypes independent of BMI.
- partial: Prevalence of insulin resistance in the polycystic ovary syndrome using the homeostasis mo… (Fertility and sterility 2005) · cited 591x in the literature
"In patients with PCOS, the prevalence of IR was 64% according to the HOMA-IR measurement, after adjustment. Patients with IR were more clinically affected. Although IR is a common abnormality in PCOS, it does not seem to be a universal feature." (abstract, conclusions, passage verified)
pubmedfull study (doi) - supports: Insulin resistance in polycystic ovary syndrome: a systematic review and meta-analysis of … (Human reproduction (Oxford, England) 2016) · cited 403x in the literature
"Overall IS was lower in women with PCOS compared with controls (mean effect -27%, 99% CI ±6%; large, most likely lower). A higher BMI exacerbated the reduction in IS by -15% (±8%; moderate, most likely lower) in PCOS compared with control women." (abstract, results, passage verified)
pubmedfull study (doi) - partial: Insulin resistance in a large cohort of women with polycystic ovary syndrome: a comparison… (Human reproduction (Oxford, England) 2017) · cited 157x in the literature
"Overall, insulin resistance, as identified by the M-clamp value, was found in 74.9% of these women. The percentage was 59.3% in normal-weight vs 77.5% in overweight and 93.9% in obese subjects." (abstract, results, passage verified)
pubmedfull study (doi)
Only about 3% of the population does well with less than seven hours of sleep per night.
"And we also know that only about 3% of the population does well with less than seven hours of sleep." (said at 0:32:34)
Sleep medicine guidelines and epidemiological studies generally recommend at least 7 hours of sleep per night for adults, noting that genuine "natural short sleepers"—individuals who thrive, maintain normal cognitive function, and experience minimal daytime impairment on less than 7 hours of sleep without accumulating sleep debt—represent a rare segment of the general population (often estimated at around 1% to 3%). However, precise population prevalence estimates remain challenging to verify because rare Mendelian genetic variants associated with familial natural short sleep (such as mutations in BHLHE41/DEC2, ADRB1, NPSR1, and GRM1) are extremely rare and show variable penetrance in large population biobanks. Furthermore, objective laboratory studies indicate that many individuals who subjectively believe they function well on short sleep demonstrate measurable objective drowsiness and microsleeps under low-stimulation conditions.
- context: Some Twist of Molecular Circuitry Fast Forwards Overnight Sleep Hours: A Systematic Review… (Cureus 2021) · cited 4x in the literature
"Due to the rare prevalence, the number of studies conducted on natural short sleepers is limited... Natural short sleep traits in either point-mutations or single null mutations in those genes have been examined and confirmed its intrinsic nature in affected individuals without any related health concerns." (abstract, results)
pubmedfull study (doi) - context: The impact of Mendelian sleep and circadian genetic variants in a population setting. (PLoS genetics 2022) · cited 8x in the literature
"Rare variants in ten genes have been reported to cause Mendelian sleep conditions characterised by extreme sleep duration or timing. These include familial natural short sleep (ADRB1, DEC2/BHLHE41, GRM1 and NPSR1)... Our results indicate that previously reported variants for Mendelian sleep and circadian conditions are often not highly penetrant when ascertained incidentally from the general population." (abstract, results and conclusions, passage verified)
pubmedfull study (doi) - context: Sleepy without stimulation: subjective and objective sleepiness in actigraphy-verified nat… (Journal of sleep research 2024) · cited 2x in the literature
"Natural short sleepers (NSS)-individuals who report minimal sleepiness or daytime dysfunction despite habitually sleeping less than the recommended amount (i.e., <7 h)-are a focus of growing interest in sleep research. Yet, the predominance of research on NSS has relied on subjective reports of functionality." (abstract, introduction, passage verified)
pubmedfull study (doi)
The average American woman consumes only about 12 grams of dietary fiber per day.
"and it's sad to me to realize that on average an American woman gets about 12 grams of fiber a day." (said at 0:40:45)
The speaker is correct that American women consume substantially less dietary fiber than recommended (the adequate intake is 25–28 g/day), but the actual national average is slightly higher than 12 grams per day. Nationally representative data from the National Health and Nutrition Examination Survey (NHANES) report average daily fiber intakes among adult U.S. women between roughly 14.8 g/day and 15.4 g/day (for example, 15.4 g/day in women aged 19–50 and 14.8 g/day in postmenopausal women), with subgroups such as non-Hispanic Black women averaging closer to 12–13 g/day.
Carriers of the APOE4 allele have a significantly greater accumulation of beta-amyloid in the brain if they are insulin resistant.
"For example, some of the stuff I presented at the conference that you and I were attending showed that while there is a significant increased risk for accumulation of beta-amyloid in your brain if you have the APOE4 allele, that risk is hugely increased carrying the amyloid in your brain if you are insulin resistant." (said at 0:50:15)
Longitudinal cohort data show that midlife insulin resistance is an independent predictor of late-life brain beta-amyloid accumulation on PET imaging (tripling the odds of amyloid positivity), but this increased risk is observed in both APOE ε4 carriers and non-carriers rather than being an effect exclusive to or synergistic with APOE4.
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.