Biohack Bracket.
12 head-to-head matchups. Pick the one you'd actually do. At the end, see your personal bracket and the global leaderboard.
Tap one. No going back.
Is cold plunge better than sauna for longevity?+
On hard endpoints, sauna has the stronger evidence. The Finnish KIHD cohort (Laukkanen 2015) found 4–7 sessions/week of 20+ minutes at 80–100°C cut fatal cardiovascular events ~50% and all-cause mortality ~40% over 20 years. Cold plunge improves brown-fat activation and insulin sensitivity in small studies but has no comparable cohort data. If you can only do one, sauna wins on evidence.
Fasting vs keto — which is better?+
They're different tools for different problems. Intermittent fasting (16:8, OMAD) is primarily a calorie-management lever — most of the benefits in human trials track to calorie deficit, not autophagy. Keto is a metabolic-state intervention that's useful for specific cases (refractory epilepsy, some metabolic syndromes). For most people, time-restricted eating without strict keto delivers most of the metabolic upside with much better adherence.
Zone 2 vs HIIT — which is more important?+
Both, in an 80/20 split. Zone 2 (180+ min/week, conversational pace) builds mitochondrial density and fat oxidation. HIIT (1–2 sessions/week, Norwegian 4×4 protocol) is the strongest single lever for raising VO2 max. Doing only one plateaus the other.
Creatine vs NMN — which has more evidence?+
Creatine — by a wide margin. Creatine monohydrate at 3–5 g/day has decades of RCTs showing strength, lean mass, and increasingly cognitive benefits. NMN raises blood NAD+ in humans but no RCT yet shows it changes hard outcomes. If you're picking one, creatine is the cleaner risk/benefit profile.
How is the bracket scored?+
Each pairwise pick adds a win for the chosen option and a loss for the other. The leaderboard ranks every item by win rate (wins / total matchups), so items that appear in more pairs are still comparable to items that appear in fewer.
Why can't I undo a pick?+
Each pick is logged the moment you tap it — that's how the leaderboard updates in real time. The next-matchup flow is one-way to keep the data clean (no flipping votes after seeing what the community chose).
Cold plunge vs sauna — what the evidence shows
Sauna has the larger and more consistent evidence base for hard endpoints. The Finnish KIHD cohort (Laukkanen 2015) found 4–7 sauna sessions per week (≥20 min at 80–100 °C) cut fatal cardiovascular events by ~50% and all-cause mortality by ~40% vs 1 session per week, over a 20-year follow-up of 2,315 men. Cold plunge has no comparable cohort data; the most-cited paper (Søberg 2021) showed brown-fat activation and improved insulin sensitivity in 8 cold-water swimmers vs controls. If you can only do one, sauna wins on evidence; cold plunge wins on mood/dopamine in the short term.
Zone 2 vs HIIT — both, in different doses
Zone 2 (conversational pace, ~60–70% max HR) is the volume engine for mitochondrial density and fat oxidation. Attia's standard prescription is 180+ minutes per week split across 3–4 sessions. HIIT (Norwegian 4×4, Tabata, sprints) is the peak-VO2-max lever — even 1 weekly session moves VO2 max measurably (Helgerud 2007). Practical split for healthy adults: ~80% Zone 2, ~20% HIIT. Doing only HIIT plateaus VO2 max gains and increases injury risk; doing only Zone 2 caps the top of your cardiorespiratory ceiling.
Creatine vs NMN — different problems
Creatine monohydrate is the most evidence-backed supplement in sports science: 3–5 g/day improves strength, lean mass, and (per recent meta-analyses) memory and processing speed in adults. NMN raises blood NAD+ in humans (Yoshino 2021) but no RCT yet shows it changes hard outcomes — longevity, function, or biomarker shifts beyond NAD+ itself. If you're picking one, creatine has the cleaner risk/benefit profile. NMN is a bet on the underlying biology of NAD+ decline being causal.
- Laukkanen T, et al. Association between sauna bathing and fatal cardiovascular events. JAMA Intern Med. 2015;175(4):542-548.
- Søberg S, et al. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine. 2021;2(10):100408.
- Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-71.
- Yoshino M, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224-1229.
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