Chapter 23 — Key Takeaways

One page. ⚠️ Opens Part V — six ✅ verdicts, more than any chapter so far.**

⚠️ The Hierarchy — and attention runs almost exactly in reverse

Rows 6 and 7 get the podcasts, the products and the arguments. Rows 1 and 2 decide the race.

✅ Energy Availability (§23.2)

EA = (intake − exercise expenditure) ÷ fat-free mass. ⚠️ The energy left for everything that isn't the session — hormones, bone, immune function, menstrual cycling, repair.

~45 kcal/kg FFM supports full function; below ~30, consequences are consistently observed. RED-S (IOC consensus, evolving from the Female Athlete Triad) — bone, endocrine, menstrual, metabolic, immune, cardiovascular, GI, psychological — ⚠️ in athletes of any sex.

⚠️ PERFORMANCE DECLINE IS ONE OF THE LAST THINGS TO GO. By the time the times slow, bone, hormones and immunity have been in deficit for months. "My times are fine" is not reassurance.

Watch instead: menstrual irregularity (⚠️ never normal) · bone stress injuries · recurrent illness · poor recovery between sessions · poor sleep · low ferritin · reduced libido · frequent minor injuries · mood change.

✅ Carbohydrate (§23.3)

⚠️ The dose is a function of the LOAD. "Carbs are good for athletes" isn't the answer — the table is. Someone training three hours a week does not need 8 g/kg.

The storage table that explains three things at once

Hence: loading works · breakfast before a morning session matters · and ⚠️ "the wall" (muscle — legs fine, pace gone) and "the bonk" (liver, blood glucose — lightheaded, confused) are different events.

Total ~400–500 g ≈ 1,600–2,000 kcal. A marathon costs ~2,400–2,800. ⚠️ The tank holds less than the race. That's the whole of "the wall," and it's arithmetic.

✅ During Exercise (§23.5)

⚠️ SGLT1 saturates at ~60 g/h. Fructose uses GLUT5 — a separate door. Glucose+fructose (~2:1) recruits both, permits higher rates, and causes less GI distress, because unabsorbed carbohydrate in the gut is what causes the distress. (Chapter 15's ORS co-transport, exploited again.)

⚠️ AND THE GUT IS TRAINABLE. Attempting 90 g/h for the first time on race day is the most reliable way to vomit at km 25. Case Study 1: ten weeks, 25 g total → 75 g/h.

Protein, and the Window (§23.6)

1.4–2.0 g/kg/day · toward 2.0–2.4 in a deficit · ~0.3 g/kg per meal, 3–5×/day · ~2–3 g leucine.

🟠 The "30–60 minute anabolic window." ⚠️ The window is HOURS — muscle stays sensitized for at least 24 h post-resistance-exercise, and total daily protein plus distribution matter more. 🟢 Distribution is real. ⚠️ (Exception: fasted training, or another session within ~8 h — that's a refuelling problem, not a synthesis one.)

🟠 Low-Carb Endurance (§23.7)

✅ Fat adaptation is real — keto-adapted ultra-endurance athletes reach fat oxidation rates well above classical maxima (FASTER, cross-sectional).

⚠️ And the race-walker work tested performance directly: LCHF raised fat oxidation as predicted AND IMPAIRED EXERCISE ECONOMY. High-carbohydrate and periodized groups improved race performance; LCHF did not.

⚠️ Mechanism: fat oxidation costs more oxygen per unit ATP. Irrelevant submaximally; a direct penalty where oxygen delivery is the constraint. "Fat-adapted" is a TRADE, not an upgrade.

🟡 Genuinely unclear for ultra-endurance at low relative intensities.

🟡 Train-Low (§23.4)

⚠️ Signalling robust (AMPK, p38 MAPK, PGC-1α); performance outcomes inconsistent — because you can't train as hard with low glycogen and training quality drives adaptation. ⚠️ Easy to do badly: a poorly-executed train-low programme is indistinguishable from chronic under-fuelling.

Hydration (§23.8)

🟢 Drink to thirst is adequate for most, in most conditions. ✅ ⚠️ Programmed over-drinking is dangerous — exercise-associated hyponatremia (Ch 15). >2% body mass loss impairs performance in heat. ⚠️ Sweat sodium varies ~tenfold (200–2,000 mg/L) and is largely fixed.

Free indicators of a salty sweater: ⚠️ white crusting on skin/kit/cap · sweat stings the eyes. And the practical answer is table salt — ¼–½ tsp in a carbohydrate bottle does what a sachet does. ⚠️ Commercial products earn their premium on convenience and taste, not composition.

⚠️ Measure your sweat rate once: weigh before and after one hour, add fluid drunk.

The Five That Work (§23.9)

Plus ✅ iron in deficient athletes — ⚠️ not an ergogenic aid; correcting a deficiency that was destroying performance (Ch 14, Devi).

⚠️ Worth ~1–3%. Elite: a final versus a heat. Everyone else: smaller than the variation between two Tuesdays — and buying the elite stack while leaving rows 1–4 untouched is the smallest available intervention.

🟠/❌: BCAAs · glutamine · testosterone boosters · most pre-workouts (caffeine at an undisclosed dose). ⚗️ ketone esters. 🟡 collagen, tart cherry, HMB.

⚠️ Strict Liability

You are responsible for what is in your body, regardless of how it got there. ✅ Only batch-level third-party certified products — NSF Certified for Sport, Informed Sport. ⚠️ Highest risk: weight loss, pre-workout, "testosterone support," proprietary blends. Keep the tub. 1–3% against a multi-year sanction: the arithmetic is not close.

Recovery (§23.11)

1. Refuel — ⚠️ 1–1.2 g/kg/h for the first hours IF the next hard session is <8 h away; otherwise daily total matters and urgency doesn't. 2. Repair — 0.3 g/kg, repeat every 3–5 h. 3. Rehydrate — 125–150% of the deficit, with sodium (Ch 15 §15.6). 4. ⚠️ REST.

⚠️ Sleep has the largest effect size and the smallest market. Restriction impairs glycogen resynthesis, training quality, immunity, injury risk and the hormonal environment for adaptation. ⚠️ An evening caffeine dose can cost more in sleep than it delivered in the session.

⚠️ The Recreational Correction (§23.12)

3–5 g/kg carbohydrate · 1.4–1.6 g/kg protein · ⚠️ no in-session fuelling under 75 min · drink to thirst · creatine if you lift, caffeine if you tolerate it, and that's it.

⚠️ Importing elite fuelling into a non-elite training load reliably produces weight gain, which then gets blamed on the training. Chapter 4's arithmetic doesn't care that the calories came in a gel.

⚠️ §23.13 — Body Composition

Both true: composition genuinely affects performance in some sports, AND its pursuit causes documented harm.

⚠️ Lighter is not monotonically faster — the relationship is a curve with a peak, and most athletes trying to get lighter are past it. Rapid loss impairs performance reliably. Weight-making in combat sports carries documented serious risk including deaths, and has prompted governing-body rule changes.

⚠️ The modifiable risk factor available today at zero cost: stop commenting on athletes' bodies.

⚠️ Two Limits on This Chapter's Evidence

The literature is substantially male — the fuelling numbers scale to mass and load and probably transfer; the timing, adaptation and supplement specifics transfer less. And almost all of it is short-term — ⚠️ excellent about a time trial next Tuesday, thin about a twenty-year career. Which is exactly why energy availability sits at the top.

🧾 Economics

Creatine $40–70 · caffeine $0–40 · ⚠️ home-mixed carbohydrate + salt $25–50 · bicarbonate $5 · sweat testing $0** — versus — **branded gels/drinks $700–1,400 · daily electrolyte sachets $220–730 · a pre-workout $584 · BCAA and "recovery" blends $300–900.

⚠️ Sucrose is one glucose bonded to one fructose (Ch 18 §18.2) — which is why sugar, salt and water works, and why the expensive version is expensive for taste, convenience and packaging.

Twelfth consecutive chapter where the best-evidenced option is the cheapest.

One Thing to Remember

⚠️ Devi didn't get fitter. Her fitness had been there for two years.

She ate enough, matched carbohydrate to her load, fixed her iron, and fuelled during the race — and kilometre 32 didn't happen.

"I kept waiting for it. I got to 35 and thought — oh. That's just what it's supposed to feel like."