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Evidence-based guides on fitness, nutrition, and understanding health metrics.
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Your Due Date Is a Distribution, Not a Deadline
Why "Exact Age in Years, Months, and Days" Has More Than One Right Answer — and What Happens If You're Born on Feb 29
"33 years, 9 months, 21 days" sounds precise — but because months have different lengths, the algorithm used to calculate the "months and days" portion involves a genuine implementation choice that can produce different results for the same two dates. Here's how the year/month/day "borrowing" algorithm works, why February 29th birthdays create a recurring ambiguity with real legal implications, and why "months" as a unit is inherently approximate.
"Ideal Weight" Gives You One Number — Health Guidance Gives You a Range, and the Difference Matters
"Ideal weight" formulas all output a single number — but health guidance (BMI ranges) is expressed as ranges, not single targets, and the gap between "a single target" and "a healthy range" matters for how people relate to these numbers. Here's why single-number framing can create "missed the target" feelings even within a healthy range, why it can encourage precision-seeking behaviors that body-fat-tracking articles already cautioned against, and why "healthy weight range" is generally the more useful framing.
DEXA, BIA, Calipers, and Hydrostatic Weighing: How Body Fat Measurement Methods Compare
DEXA, hydrostatic weighing, BIA scales, and skinfold calipers can give different body fat percentages for the same person on the same day. Here's what each method actually measures, why BIA scales are so sensitive to hydration, and how to choose between accuracy and practicality for tracking your own body composition.
Muscle, Metabolism, and Aging: Why Sarcopenia — Not "Slowing Down" — Explains Metabolic Change
A landmark study tracking 6,400 people found metabolism is remarkably stable from age 20 to 60 — what actually changes is muscle mass. Here's the Pontzer 2021 findings, how sarcopenia drives the "skinny fat" phenomenon, why protein needs increase with age, and why resistance training is the primary evidence-based intervention.
Ketogenic Diets and Nutritional Ketosis: What the Research Shows About Weight Loss, Performance, and Who Should Be Cautious
Ketogenic diets shift the body's fuel source from glucose to fat and ketones — a measurable metabolic state with the strongest evidence base in drug-resistant epilepsy. Here's how nutritional ketosis differs from dangerous diabetic ketoacidosis, what weight loss research actually shows over longer timeframes, and the mixed evidence on athletic performance.
Harris-Benedict vs Mifflin-St Jeor vs Katch-McArdle: Why BMR Formulas Disagree by 100-200 Calories
BMR calculators don't all use the same formula — Harris-Benedict (1919, revised 1984), Mifflin-St Jeor (1990), and Katch-McArdle (lean-mass-based) can disagree by 100-200 calories for the same person, which represents 20-30% of a typical weight-loss deficit. Here's how each formula was developed, why they diverge more for people at the extremes of body composition, and why any formula's output should be treated as a starting point rather than a precise target.
BMI and Pregnancy: Why Pre-Pregnancy BMI Matters and "Current BMI" During Pregnancy Doesn't Mean What You'd Think
A pregnant person's BMI increases throughout pregnancy simply because of the pregnancy itself — applying standard BMI categories to this changing number would be meaningless. Here's why clinical weight-gain guidance uses pre-pregnancy BMI as a fixed reference point instead, why "total weight gain from that reference point" is the relevant question rather than "current BMI category," and how postpartum BMI takes time to become meaningful again.
BMI and Ethnicity: Why the WHO Recommends Lower Thresholds for Asian Populations
A BMI of 24 is "normal" by standard categories but already represents "increased risk" under WHO's Asian-specific BMI cut-offs (23 for overweight, 27.5 for obese). Here's why these adjustments exist, the body composition research behind them, UK NICE guidance for multiple ethnic groups, and why waist circumference complements BMI across populations.
EPOC, the "Afterburn Effect," and HIIT vs Steady-State: Separating Research from Marketing
EPOC ("afterburn") adds approximately 6-15% to a workout's calorie burn — real, but smaller than fitness marketing implies. Here's what EPOC actually measures, why HIIT's real advantage is time efficiency rather than metabolic magic, how HIIT and steady-state compare for fat loss, and how resistance training's EPOC differs from cardio's.
Intermittent Fasting and Meal Timing: Does When You Eat Actually Matter?
Intermittent fasting's weight loss effect appears to come largely from spontaneous calorie reduction, not a separate metabolic pathway — but circadian research suggests eating earlier in the day may benefit glucose tolerance independent of weight. Here's what controlled trials actually show about meal timing, autophagy claims in context, and who IF tends to suit.
Twin Pregnancy Due Dates, Chorionicity, and IVF Dating: How Multiple Pregnancies Differ
Twin pregnancies average 36-37 weeks rather than 40 — meaning a standard due date calculation represents a date most twin pregnancies won't reach. Here's why multiples arrive earlier, how chorionicity affects monitoring and timing, why IVF dating from embryo transfer is the most precise method available, and what vanishing twin syndrome means for dating.
Why Ideal Weight Formulas Break Down for Athletes and Anyone With Above-Average Muscle Mass
A bodybuilder at 95kg with 8% body fat and a sedentary man at 95kg with 30% body fat get an identical "ideal weight" from every classic formula — because none of them account for muscle mass. Here's why NFL linemen and Olympic weightlifters routinely fall into "obese" categories by BMI and ideal weight formulas, and what's actually useful for athletic populations instead.
