IndexBody Journal

Evidence-based articles on fat loss, body composition, nutrition, and fitness. All written and reviewed by Dr. Sarah Mitchell, M.D. with citations to peer-reviewed research.

Each guide below is meant to be read alongside our free calculators: the calculators give you a number (your BMI, BMR, TDEE, or estimated body fat percentage), and these articles explain what that number means, where the underlying formula comes from, and what its limitations are. Nothing here replaces individualized advice from a doctor, registered dietitian, or other qualified healthcare provider — use these articles to understand the math, not as a substitute for medical care.

Fat LossBody CompositionNutritionMetabolism & EnergyFitness & TrainingWellness

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Most Read · Body Composition
What Is BMI? Complete Guide
WHO classifications, limitations, and better alternatives explained.
Most Read · Nutrition
How Many Calories Should I Eat?
Mifflin-St Jeor equation explained with real examples.
Essential · Fat Loss
How to Calculate a Calorie Deficit
Step-by-step with real numbers. Safe vs aggressive deficit explained.

Body Composition

Body Composition
What Is BMI? Complete Guide
WHO classifications, limitations, and better alternatives.
Body Composition
BMI vs Body Fat: Which Is Better?
Why body fat % outperforms BMI for most people.
Body Composition
Body Fat % Explained
Healthy ranges by age and sex, how to measure accurately.
Body Composition
BMI for Men: Complete Guide
How BMI applies to males — visceral fat, athletes, and more.
Body Composition
BMI for Women: Complete Guide
Hormonal differences, menopause, and pregnancy considerations.
Body Composition
Healthy Body Fat by Age
ACE reference ranges for every age group and goal.
Body Composition
Waist-to-Height Ratio Guide
The single measurement that predicts disease better than BMI.