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Evidence-based guides on fitness, nutrition, and understanding health metrics.
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Your Cycle's Range Tells You More Than Its Average
Why Caffeine Causes a Crash — Adenosine, the Two-Process Sleep Model, and the Science of Strategic Napping
Caffeine blocks adenosine receptors but doesn't clear the accumulated adenosine — when it's metabolised, adenosine floods the now-unblocked receptors, causing a crash proportional to the sleep debt built up while caffeine was present. Here's the two-process model of sleep (adenosine pressure plus the circadian clock), how the SCN's 24-hour molecular oscillation works, why SWS rebound is prioritised over REM in recovery sleep, and the biomechanics behind the "nappuccino" being more effective than either caffeine or napping alone.
Fibre Is a Carbohydrate That Doesn't Behave Like One — Gut Bacteria, Short-Chain Fatty Acids, and the Net Carbs Calculation
Dietary fibre is technically a carbohydrate but produces only 0-2 kcal/g instead of the 4 kcal/g that macro calculators assume — because human enzymes can't digest it. Here's how gut bacteria ferment soluble fibre into butyrate, propionate, and acetate (the SCFAs that maintain colon health and signal appetite to the brain), why Western adults eat only 15-19g daily against a 25-38g recommendation, and the net carbs calculation for keto tracking.
The Devine Ideal Weight Formula Came From a Drug Dosing Paper — Here's What Actual Health Outcomes Research Shows Instead
The Devine ideal weight formula appeared in a 1974 drug dosing paper — it was never derived from health outcome research. Here's where each major formula came from (insurance actuarial tables, drug pharmacokinetics, military studies), what mortality outcome data actually shows about "healthy" weight (lowest mortality at BMI 22-25 but the curve is flat 20-27), and why the obesity paradox in clinical populations complicates the "lower is healthier" framing.
Dutch Men Grew 18 cm Taller in 130 Years Without Changing Genes — The Secular Height Trend Explained
Dutch men grew 18 cm taller in 130 years — genetics don't change that fast, so the entire increase came from nutrition and disease improvements. North and South Koreans are genetically identical but differ by ~9 cm in average height from 50 years of divergent nutrition. Here's the secular height trend, why "80% heritable" doesn't mean what people think it means, and why contemporary height differences between populations are mostly environmental history, not genetics.
Perimenopause's First Sign Is Cycle Variability, Not Hot Flushes — What to Track and When to See a GP
Perimenopause's first sign isn't hot flushes — it's cycle length variability, with reliably predictable cycles becoming erratic over 2-10 years before the final period. Here's how declining ovarian reserve drives follicular phase variability, why anovulatory cycles cause heavier periods, the specific tracking patterns that indicate perimenopause vs thyroid issues or PCOS, and why fertility doesn't reach zero until 12 months after the final period.
Why Your 40-Week Due Date Is Actually 38 Weeks of Pregnancy — Ultrasound Dating, Naegele's Rule, and When Induction Is Recommended
A 40-week pregnancy is actually ~38 weeks of fetal development — gestational age is counted from 2 weeks before fertilisation. First-trimester ultrasound (±5 days accuracy) is more accurate than LMP dating for anyone with irregular cycles. Here's why the due date is a median with an asymmetric range, what the ARRIVE trial says about 39-week induction, and why gestational age accuracy matters most in preterm delivery decisions.
Why Your Exercise Calorie Estimates Are Systematically Too High — NEAT Compensation, Dose-Response, and the Muscle Mass Advantage
Adding up exercise calorie estimates to calculate weekly expenditure overstates the benefit by 30-50% — because NEAT drops on exercise days, appetite partially compensates, and training efficiency improves. Here's the dose-response relationship between volume and actual burn, why MET values have a ±20-30% accuracy ceiling, the long-term resting metabolism boost from added muscle (13-22 kcal/kg/day), and why fasted exercise doesn't reliably burn more fat over 24 hours.
Why 100 Calories of Protein Doesn't Equal 100 Calories of Carbs — The Thermic Effect of Food and What It Means for Your Calorie Target
Protein burns 20-30% of its own calories just in digestion — eat 100 calories of protein and you net roughly 70-80 calories. Fat burns only 0-3%. This "thermic effect of food" means macronutrient composition changes your effective calorie intake even if the label says the same total. Here's the full TEF breakdown, why it matters for calorie targets, and how high-protein diets exploit it.
Brown Fat Was "Only in Babies" Until 2009 — The Thermogenesis Biology That Changes How We Understand BMR
Brown adipose tissue was thought to exist only in infants until 2009, when PET/CT scans revealed metabolically active brown fat in adults — concentrated around the neck and collarbones, inversely correlated with BMI. Here's the white vs brown vs beige fat distinction (storage vs heat generation vs metabolic plasticity), how cold activates UCP1 thermogenesis adding 100-300 kcal/day, and why thyroid hormone is the primary BMR regulator that calculators completely ignore.
Metabolic Syndrome Predicts Heart Disease Better Than BMI — Here's What the Five Criteria Are and Why They Matter More
Metabolic syndrome — any three of five criteria (waist circumference, triglycerides, HDL, blood pressure, fasting glucose) — predicts cardiovascular disease better than BMI alone, and "TOFI" individuals (normal BMI, high visceral fat) are misclassified as healthy by BMI. Here's the complete metabolic syndrome criteria, A Body Shape Index (ABSI) as the next-generation abdominal obesity measure, the obesity paradox in clinical populations, and why WHtR is emerging as the recommended companion to BMI.
Why "Drink to Thirst" Fails at Altitude — and the Specific Contexts Where You Need More Water Than General Guidance Suggests
Altitude dehydration is real because respiratory rate increases and inspired air is drier — but thirst doesn't compensate fully, making trekkers a specific population where "drink to thirst" systematically underestimates needs. Here's the quantified altitude respiratory water loss (up to 1,200 mL/day at high altitude), the fever rule of thumb (each 1°C above normal adds ~20-25% water loss), why coffee's diuretic effect is smaller than its fluid content, and the specific kidney stone prevention fluid target (2.5 litres urine output daily).
Processing Speed Peaks at 25, Vocabulary at 65 — Why "Peak Age" Depends Entirely on What You're Measuring
Cognitive processing speed peaks at 18-25, but vocabulary peaks in the late 60s, emotional regulation improves into the 70s, and crystallized intelligence doesn't decline until the 70s-80s. Here's the multiple-peaks framework for human performance, why processing speed loss doesn't translate to overall cognitive decline (strategy, knowledge, metacognition compensate), why marathon runners peak later than sprinters, and the relative age effect that makes September-born UK children more likely to be identified as gifted.
