Nutrition — Performance-Framed, Evidence-First

Most nutrition advice is written for weight loss and measured on a scale. That framing misses what actually matters for a long healthspan: preserving muscle, keeping ApoB and fasting insulin low, and fueling training well enough to keep doing it for decades. Those goals sometimes conflict with the advice that produces the fastest scale movement.

This hub is framed around performance and lab values instead. How much protein you need at your body weight and age. What each fasting protocol actually delivers versus what it is marketed as delivering. Why meal timing gets far more attention than its effect size justifies. And which dietary changes reliably move which biomarkers, with the timelines for retesting.

Protein: the target that most people miss

Protein is the macronutrient with the clearest dose-response and the widest gap between the official recommendation and the useful one. The RDA of 0.36g per pound exists to prevent deficiency in a sedentary adult. It is not the intake associated with preserving muscle across decades, and it is roughly half of what resistance-training research supports.

The per-meal row is the one most people overlook. Muscle protein synthesis responds to a leucine threshold of roughly 2.5–3g, which takes about 30–40g of a high-quality protein to reach. Three meals of 40g each drive a better response than 20g at breakfast, 30g at lunch, and 70g at dinner — even though both add up to 120g. After 50, anabolic resistance raises the per-meal requirement further, which is why older adults eating a protein-light breakfast lose ground even at an acceptable daily total.

Fasting protocols: what each one actually does

Fasting is the most oversold area in longevity nutrition. The animal autophagy data is genuinely interesting; the human outcome data is much thinner than the popular coverage suggests. Here is what the protocols do when compared against calorie-matched eating rather than against no intervention.

Fueling Zone 2 and hard training

Zone 2 is the aerobic base work done at roughly 60–70% of maximum heart rate, where you can hold a conversation but would rather not. Most protocols call for 150–180 minutes a week across 3–4 sessions. The fueling question splits by duration.

• Under 90 minutes. No fuel needed. Training with moderate glycogen availability is part of the stimulus for fat oxidation and mitochondrial adaptation.
• Over 90 minutes. Take 30–60g of carbohydrate per hour. Past this point the fatigue cost starts undermining the volume you are trying to accumulate.
• High-intensity intervals or heavy lifting. Fuel these. Glycolytic work depends on glycogen, and doing it depleted lowers session quality without any compensating adaptation.
• The common mistake. Fasting every Zone 2 session. Fat-oxidation gains are real but small next to the gains from total accumulated volume, and chronic under-fueling suppresses that volume — along with thyroid output, testosterone, and, in women, menstrual regularity.

Which changes move which biomarkers, and how fast

The single most useful thing to know before changing your diet is when to retest. Retest too early and a working change looks like a failure. The intervals below are set by the biology of each marker, not by convention.

Two of these have hard biological floors on the retest interval. HbA1c reflects roughly 90 days of average glucose because it is bound to red blood cells, which live about 120 days — so a 6-week retest reports mostly the old diet. The omega-3 index has the same constraint for the same reason. Testing either at 4 weeks wastes the test.

Fasting

• Fasting protocol guide — 16:8, OMAD, and extended fasts
• Does fasting lower blood pressure?
• Why weight loss plateaus — what adaptation, appetite and under-reporting actually contribute

Macronutrients and performance

• Foods that lower cholesterol The measured effect sizes for sterols, oats, nuts and soy
• Low-dose and "microdosed" GLP-1 evidence — what the pivotal trials measured at each dose, and what the registries show for sub-labelled maintenance
• Anti-inflammatory diet — the hsCRP reduction randomised Mediterranean-diet trials actually produced, and which part of the pattern carried it
• Protein timing for recovery and muscle after 40
• Zone 2 cardio — how much, how often, and why
• Walking for heart health — where the step-count curve flattens, how far the meta-analyses disagree, and the numbers walking does not move
• Zone 2 vs HIIT — different cellular pathways, and no trial showing either one wins on survival
• Zone 2 heart rate by age — the age-banded numbers, and the prediction error that is wider than the zone
• Zone 2 heart rate too high — why the calculator is usually wrong rather than your heart
• Zone 2 for fat loss — fat oxidation during a session is not fat loss over weeks
• Zone 2 walking — who reaches it on the flat, and why grade beats pace as the fix
• Zone 2 heart rate vs power — four zone models, four different things called Zone 2
• VO2 max — what the measure is, how it is tested, and the common reasons it falls
• VO2 max by age — percentile charts for men and women, from the FRIEND registry

Body composition and hormones

• Visceral fat — the fat depot that drives hsCRP and insulin resistance, how it is measured, and what actually reduces it
• Insulin resistance diet: the three eating patterns with randomised trial evidence behind them
• Insulin resistance and weight loss: why the same deficit returns less, and where GLP-1 medication fits
• GLP-1 and the brain — the appetite mechanism is settled; the phase 3 Alzheimer's trials did not slow the disease
• Retatrutide vs tirzepatide — a phase 2 triple agonist against a drug with phase 3 results behind it
• Semaglutide vs tirzepatide — the two molecules head to head, and what SURMOUNT and STEP each measured
• Ozempic vs Wegovy — the same molecule under two approvals, with different indications and labels
• Zepbound vs Wegovy — tirzepatide against semaglutide where both carry a weight-loss indication
• Mounjaro vs Wegovy — the same two molecules under their diabetes and weight-loss brands, and what SURPASS-2 and SURMOUNT-5 each measured
• Compounded vs brand semaglutide — what FDA approval covers, and what a compounding pharmacy changes
• Semaglutide side effects — the label's own frequency tables against placebo, the boxed warning, and which feared effects the evidence does not support
• Semaglutide side effects timeline — why the pattern follows the dose step rather than the injection, and what the trials record about how long each episode lasts
• At what age is it hardest to lose weight: what the doubly labelled water data show about metabolism across the lifespan, and why the answer is not the one folklore gives
• Visceral fat level chart — what the 1 to 59 number on a body-composition scale means, and why two brands disagree
• Does soy lower testosterone? — what the trial evidence shows, and where the claim came from

Heat and Cold Exposure

• Sauna benefits: what the Finnish cohort evidence supports, the dose that produced it, and what it does not support
• Infrared vs traditional sauna: why the evidence attached to one does not transfer to the other
• Cold plunge benefits: the mood evidence, the hypertrophy cost, and the temperature and duration the trials used
• Sauna vs cold plunge: which to pick if you can only have one, and which order to do them in
• Hyperbaric oxygen therapy: the conditions a payer actually covers, set against what longevity clinics sell it for

Related

• Biomarker guides — the labs that tell you whether a diet change worked
• ApoB — the lipid marker most responsive to diet
• Fasting insulin and HOMA-IR
• Nutrient density — where the micronutrients come from
• Supplement guides — what to add once the diet is handled