In the latest episode of his Overrated/Underrated series, Dr. Layne Norton ranks the habits, markers, and gadgets the longevity and biohacker crowd won’t stop talking about. No hype. No bro-science. Just what the data actually says about what predicts a longer life, and what has been oversold as a hack.
Topics covered: VO2 max, grip strength, cold plunges, sauna, sleep trackers, muscle mass, fasting, biological age tests, and more!
Tune in for evidence-based analysis and practical tips on what actually moves the needle for better health and longevity.
Citations
Cardiovascular fitness / VO2 max
- Kodama et al., JAMA 2009. Each 1-MET higher cardiorespiratory fitness associated with ~13% lower all-cause mortality and ~15% lower CHD/CVD events. https://pubmed.ncbi.nlm.nih.gov/19454641/
- Lang et al., Br J Sports Med 2024. Overview of meta-analyses (>20.9 million observations): high vs low CRF, HR 0.47 for all-cause mortality; ~11–17% lower risk per 1-MET. https://pubmed.ncbi.nlm.nih.gov/38599681/
Grip strength as a surrogate for strength
- Leong et al., Lancet 2015 (PURE, ~140,000 people). Grip strength inversely associated with all-cause and cardiovascular mortality; per 5 kg lower grip, HR 1.16 for death. Authors frame it as a simple risk-stratifying measure. https://pubmed.ncbi.nlm.nih.gov/25982160/
- Cooper et al., BMJ 2010. Meta-analysis: weakest vs strongest grip quartile, HR 1.67 for mortality. https://pubmed.ncbi.nlm.nih.gov/20829298/
- Wu et al., J Am Med Dir Assoc 2017. 42 studies, ~3 million people: lowest vs highest grip, HR 1.41 all-cause mortality, 1.63 CVD. https://pubmed.ncbi.nlm.nih.gov/28549705/
Strength vs muscle mass
- Li et al., Med Sci Sports Exerc 2018 (NHANES). Low strength associated with higher mortality whether or not muscle mass was low; strength remained associated after accounting for mass. https://pubmed.ncbi.nlm.nih.gov/28991040/
- Momma et al., Br J Sports Med 2022. Muscle-strengthening activity associated with lower all-cause, CVD, total cancer, and diabetes risk (about 10–17%). https://pubmed.ncbi.nlm.nih.gov/35228201/
- Shailendra et al. / related resistance-training mortality meta-analysis: any resistance training vs none, ~15% lower all-cause mortality. https://pubmed.ncbi.nlm.nih.gov/35599175/
- Wang et al., Low skeletal muscle mass index and all-cause mortality risk in adults: A systematic review and meta-analysis of prospective cohort studies. https://pubmed.ncbi.nlm.nih.gov/37285331/
10,000 steps
- Ding et al., Lancet Public Health 2025. Inflection around 5,000–7,000 steps/day for several outcomes; 7,000 vs 2,000 steps linked to ~47% lower all-cause mortality. 10,000 still fine if you are already active. https://pubmed.ncbi.nlm.nih.gov/40713949/
- Stens et al., American College of Cardiology, 2023. Benefits from ~2,500–2,800 steps; diminishing returns near ~7,100–8,800. https://pubmed.ncbi.nlm.nih.gov/37676198/
Cold plunges and muscle growth
- Fyfe et al., J Appl Physiol 2019. Post-exercise cold-water immersion blunted type II fiber hypertrophy and anabolic signaling after resistance training; strength gains were similar. https://pubmed.ncbi.nlm.nih.gov/31513450/
- Grgic, Eur J Sport Sci 2023. Meta-analysis: cold-water immersion after lifting attenuated strength gains (effect size −0.23). https://pubmed.ncbi.nlm.nih.gov/35068365/
- Malta et al., Sports Med 2021. Regular cold-water immersion with resistance training impaired strength adaptations; endurance adaptations were not clearly harmed. https://pubmed.ncbi.nlm.nih.gov/33146851/
Sauna
- Laukkanen et al., JAMA Intern Med 2015. 4–7 sauna sessions/week vs 1: HR 0.37 for sudden cardiac death, with similar patterns for CHD, CVD, and all-cause death. https://pubmed.ncbi.nlm.nih.gov/25705824/
- Laukkanen et al., BMC Med 2018. Frequency and duration inversely associated with fatal CVD in men and women. https://pubmed.ncbi.nlm.nih.gov/30486813/
Fasting and calorie restriction
- Wisconsin rhesus study: Colman et al., Science 2009. Adult-onset ~30% restriction delayed age-related death and disease vs controls. https://pubmed.ncbi.nlm.nih.gov/19590001/
- Joint Wisconsin/NIA analysis: Mattison et al., Nat Commun 2017. Health benefits of restriction were consistent; survival differences between sites partly tracked study design and how heavy the control animals got. https://pubmed.ncbi.nlm.nih.gov/28094793/
ApoB
- Ference et al., Eur Heart J 2017 (EAS consensus). Mendelian randomization, cohorts, and trials: cumulative exposure to LDL particles causes atherosclerotic CVD in a log-linear way; lowering exposure lowers risk. https://pubmed.ncbi.nlm.nih.gov/28444290/
- Richardson et al., Lancet Healthy Longev 2021. Genetically higher apoB shortens parental lifespan and raises heart-disease risk. https://pubmed.ncbi.nlm.nih.gov/34729547/
- Yang et al., Clin Res Cardiol 2026. Meta-analysis of Mendelian randomization studies: apoB OR ~1.38 for coronary disease. https://pubmed.ncbi.nlm.nih.gov/38407584/
Psychological stress
- Busch et al., Psychol Bull 2017. Induced angry and sad rumination produce large cardiovascular responses (heart rate and blood pressure). https://pubmed.ncbi.nlm.nih.gov/29022731/
- Nie et al., J Psychosom Res 2024. Psychological interventions in CVD patients reduced cardiac mortality (RR 0.81) and myocardial infarction. https://pubmed.ncbi.nlm.nih.gov/39321711/
