Healthy Living
Practical, careful guides to body measures and daily energy. Explore the BMI and Energy & Metabolism collections.
What Is BMI and What Does It Actually Tell You?
Understand the calculation, adult categories, and limits of this familiar screening measure. Learn what this screening number can, and cannot, tell you.
Understand the number in context
What is being measured?
Learn the formula, the role of BMI as a screen, and what the number leaves out.
Read the adult ranges
See the CDC categories and interpret them without turning a range into a diagnosis.
Look beyond BMI
Compare weight-for-height with estimates of body fat, and learn why each measure has limits.
Understand body fat as an estimate
Compare tape-based estimation with other methods, learn why results change, and keep body composition separate from diagnosis.
Body Fat Calculator
Use the documented circumference equations with metric or US measurements, clear tape guidance, and visible limitations.
No universal perfect number
Learn why reference ranges vary and why lower is not automatically healthier.
See how estimates are made
Compare circumferences, skinfolds, BIA, DXA, and air displacement.
Read change carefully
Separate fat and lean-mass trends from water and measurement variability.
Understand energy from rest to a full day
Learn what resting and daily estimates describe, how the calculators connect, and why a number is not an eating target. Continue to the Calories & Energy hub for maintenance and deficit guidance.
BMR vs. TDEE: What's the Difference?
A side-by-side guide to resting and total energy use, with an example and careful calculator links.
Start with the baseline
What BMR means, what our resting equation predicts, and what it cannot measure.
See the full day
Rest, digestion, and movement contribute to total expenditure. Explore an estimate with context.
See how a discovery changed neuroscience
Learn how light-gated ion channels gave researchers a precise way to test cause and effect in selected cells.
What Is Optogenetics? The Science Behind the 2026 Nobel Prize in Medicine
How light-gated ion channels became a powerful research tool for tracing cause and effect in the brain.