Kat Fu | Longevity Strategist | The Longevity Vault

Ozempic and Sleep After 40: Why GLP-1 Side Effects Can Feel Different as You Age

Adults over 40 may have sleep vulnerabilities that make semaglutide feel different than it does in younger adults. Age-related declines in deep sleep, muscle mass, and sex hormones create a changed baseline that GLP-1 drugs can add to. Semaglutide-driven muscle loss may increase sarcopenia risk in older adults who are already losing muscle, especially when […]

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What Does Heart Rate Variability Reveal About Inflammation and Vagal Tone During Sleep?

Heart rate variability is a non-invasive window into vagal tone — the vagus nerve that suppresses inflammatory cytokines like TNF, IL-1, and IL-6 through the cholinergic anti-inflammatory pathway. A meta-analysis of 51 human studies found that lower HRV consistently correlates with higher inflammatory markers. When poor sleep suppresses vagal HRV across three or more consecutive

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Does Time-Restricted Eating Entrain Your Peripheral Clocks?

Circadian Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

Yes — but not the master clock. Meal timing is a zeitgeber for peripheral organs including the liver, kidney, and adipose tissue, but it does not move the brain’s suprachiasmatic nucleus (SCN). When you eat at odds with your light-dark cycle, your peripheral clocks move while your SCN holds its position — internal circadian misalignment.

Does Time-Restricted Eating Entrain Your Peripheral Clocks? Read Post »

Why Do Restless Legs Get Worse in Perimenopause?

Sleep & 3AM Wakeups, Women's Hormones and Sleep / Kat Fu, M.S., M.S.

Perimenopause worsens restless legs through two converging pathways. Declining and unstable estrogen disrupts dopamine regulation in the substantia nigra and thalamus — brain regions that control movement and sensory processing. Simultaneously, heavy perimenopause bleeding depletes iron stores, and the brain needs iron to produce dopamine. When estrogen instability and iron depletion hit at the same

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How Does Exercise Rebuild Your Mitochondria and Fix Your Sleep?

Metabolic Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

Exercise triggers mitochondrial biogenesis — the construction of new mitochondria — through activation of PGC-1alpha, a master regulator that responds to the energy deficit and ROS produced during physical activity. A 2024 network meta-analysis of 28 randomized controlled trials found aerobic exercise ranks first for total sleep quality (Surface Under the Cumulative Ranking Curve 93.2%).

How Does Exercise Rebuild Your Mitochondria and Fix Your Sleep? Read Post »

How Do Prostaglandins Affect Sleep?

Inflammatory Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

Your body produces two prostaglandins with opposite effects on sleep. PGD2 is the primary endogenous sleep-promoting substance identified in mammals — it drives sleep pressure through adenosine release in the brain’s ventrolateral preoptic area. PGE2 promotes wakefulness and rises during inflammation and infection. When chronic inflammation tilts the ratio toward PGE2, the result is exhaustion

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Why Do Your Eyes Get More Vulnerable to UV as You Age — Not Less?

Circadian Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

Aging eyes do receive less UV because the lens yellows and the pupil shrinks. But retinal melanin — the eye’s built-in UV shield — declines 2.5-fold and reverses from antioxidant to pro-oxidant. Aqueous humor vitamin C declines with age. Lens glutathione falls from over 20 mM to under 3 mM. The light that gets through

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Does Compounded Semaglutide Affect Sleep Differently Than Brand-Name Ozempic?

Metabolic Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

Compounded semaglutide formulations can differ from brand-name Ozempic in quality, inactive ingredients, dosing format, and added ingredients — factors that may change tolerability and sleep indirectly. Analytical testing found novel impurities in injectable follow-on semaglutide products and lower-than-labeled semaglutide content in several oral follow-on products; FDA has also noted that some compounded semaglutide products include

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Why Does NAD+ Drop Faster in Women After 40 — And What Does That Mean for Sleep?

Metabolic Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

During perimenopause and menopause, women lose NAD+ through two concurrent pathways: the age-related reduction that affects everyone, and an accelerated ovarian-specific depletion driven by rising CD38 and PARP activity in reproductive tissue. All three NAD+ synthesis pathways — kynurenine, Preiss-Handler, and salvage — show coordinated downregulation in aging oocytes (Di Emidio et al., 2024). No

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Why Are You Wired but Tired, and What Role Do Mitochondria Play?

Metabolic Sleep, Sleep & 3AM Wakeups / Kat Fu, M.S., M.S.

The wired-but-tired state is a measurable physiological condition. A meta-analysis of 20 studies found that people with chronic insomnia have elevated cortisol (SMD = 0.50), consistent with 24-hour hypothalamic-pituitary-adrenal axis hyperactivation (Dressle et al., 2022). Mitochondria sit at the center of this pattern: a PNAS study in mice demonstrated that mitochondrial function directly tunes adrenal

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