Health Tools

Muscle tissue burns roughly 3× more calories per kg at rest than fat. Sarcopenia causes 1–3% muscle loss per year from age 35 onward, gradually lowering BMR. Here's the case for resistance training as a long-term metabolic investment and the protein requirements to support it.

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.

Weekend lie-ins restore how rested you feel — but not the metabolic and cognitive damage from a week of short sleep. Here's how sleep debt accumulates, what it does to your body, and why consistency beats catch-up.

The ideal body weight formulas in most calculators were developed in the 1960s–70s for drug dosing — not for health or fitness goals. Here's what they actually measure, why they disagree, and what a more useful framework looks like.

Learn how to calculate your daily calorie needs for weight loss, maintenance, or muscle gain based on your BMR and activity level — with real examples, common misconceptions, and a free calorie intake calculator.

Your fitness tracker says 450 calories; a MET-based calculator says 320 — for the "same" workout. Both are estimates, but estimating differently: MET values are population averages applied to your weight, while wearables use proprietary heart-rate-based algorithms applied to your measured physiology. Here's why neither is "the truth," why resistance training shows larger discrepancies than steady-state cardio, and why consistency of method matters more than which method.

South Korea officially ended traditional age reckoning in 2023, where everyone ages on New Year's Day making you 1-2 years "older" than by Western count. The US drinking age of 21 is unusual globally; Germany allows beer at 16; Scotland sets adulthood at 16 for contracts. Here's how age is defined differently around the world.

Gestational age is counted from the last menstrual period — not conception — which means a "6-week pregnancy" is about 4 weeks post-conception, and "40 weeks" includes approximately 2 weeks before fertilization. Here's why different calculators give different due dates (cycle length adjustments, ultrasound overrides), what "39+4 weeks" notation means and why the days portion matters clinically, and why Naegele's 280-day rule may slightly underestimate the average first pregnancy duration.

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.

Learn what macronutrients are, how macro ratios differ by goal (fat loss, muscle gain, endurance), how to calculate your daily protein, carbs, and fat targets, and why macros matter beyond calories.