Science-Backed Guides
Health & Fitness Blog
Research explained in plain English. Every article cites its sources and links to the calculator that puts the answer to work.
All Articles
Body Composition
Is BMI Actually a Good Measure of Health?
BMI is the most widely used health screening tool in the world — but is it actually accurate? We break down the science, the limitations, and what to use instead.
Body Composition
FFMI: The Natural Limit (Kouri 1995) and How to Calculate Yours
Complete guide to the Fat-Free Mass Index — formula, normalized FFMI, the Kouri 1995 natural ceiling, scoring tables for men and women, and worked examples.
Body Composition
Navy Body Fat Calculator: How to Measure Body Fat at Home
Complete guide to the U.S. Navy body fat method — Hodgdon & Beckett (1984) formula, step-by-step measurement, accuracy vs DEXA / BIA / skinfold, body fat categories, and worked examples.
Body Composition
Why Lean Body Mass Matters More Than the Scale
The number on the scale tells you almost nothing about your health or physique. Lean body mass is the metric that actually matters — here's why.
Body Composition
The Health Risk Hidden in Your Waist-to-Hip Ratio
Where you store fat matters more than how much you store. A high waist-to-hip ratio is linked to cardiovascular disease, diabetes, and all-cause mortality.
Nutrition
TDEE Explained: How Many Calories You Burn Per Day
Complete guide to Total Daily Energy Expenditure — the Mifflin-St Jeor formula, activity multipliers, BMR formula comparison, worked examples, and how to verify your real TDEE.
Nutrition
How Much Protein Do You Need to Build Muscle? The Research Is Clear
The "1g per pound of bodyweight" rule is popular but not always evidence-based. A large meta-analysis put the number much lower — here's what the data says.
Nutrition
How Much Water Should You Drink Per Day? Beyond 8 Glasses
The "8 glasses a day" rule has no scientific basis. Your actual needs depend on body weight, activity, climate, and diet. Here's how to calculate yours.
Nutrition
Caloric Deficit: How Much to Eat for Fat Loss (Without Losing Muscle)
Complete guide to caloric deficit for fat loss — conservative vs aggressive deficits, why the 3,500 kcal rule fails (Hall 2012), metabolic adaptation, and how to preserve muscle while cutting.
Performance
One Rep Max: Epley, Brzycki, Lander Formulas Explained
Six 1RM prediction formulas compared, percentage-of-1RM training tables, RPE/RIR adjustments, worked examples, and how to estimate your 1RM safely without maxing out.
Performance
VO₂max Explained: Why It's the Most Important Fitness Number
VO₂max predicts cardiovascular disease risk better than almost any other biomarker. Here's what it measures, why it matters, and how to improve it.
Performance
Wilks Score: How to Calculate Yours and What's a Good Wilks
Complete guide to the Wilks score — formula, what's a good score for men and women, Wilks vs IPF GL Points (2020), worked examples, and how to compare strength across body weights.
Performance
Heart Rate Zones: All 5 Training Zones + Zone 2 Deep Dive
Complete guide to the 5 heart rate training zones — Tanaka and Karvonen formulas, the 80/20 polarised training rule, worked examples, and why Zone 2 builds your aerobic base.
Longevity
What Doctors Mean By Ideal Body Weight (4 Formulas Compared)
The Devine, Robinson, Miller, and Hamwi formulas all claim to define ideal body weight. They give different answers. Here's which one to trust — and why.
Longevity
Body Adiposity Index vs BMI: Which Is More Accurate?
BAI was introduced in 2011 as a BMI replacement that directly estimates body fat from hip circumference and height. Does the science support the hype?
Nutrition
How to Calculate Your Macros: The Complete Guide
Protein, carbs, and fat targets aren't one-size-fits-all. Learn how to set your macros based on your goal, activity level, and the latest ISSN guidelines.
Body Composition
What Is Visceral Fat — and Why It's More Dangerous Than Body Fat %
Not all body fat is equal. The fat packed around your organs drives cardiovascular disease and diabetes more aggressively than any other fat depot.
Performance
Running Pace: Race Pace, Riegel's Formula, and Race Time Prediction
Complete guide to running pace and race pace — Riegel's race-time prediction formula, pace conversion, the 5 Daniels training paces, grade-adjusted pace, and worked examples for 5K through marathon.
Longevity
How Much Sleep Do You Actually Need? The Science of Sleep Duration
A meta-analysis of 1.38 million people found short sleep raises mortality risk by 12%. The 7–9 hour recommendation isn't arbitrary — here's the full evidence.