Body Mass Index (BMI)
A flawed formula that ignores water weight, muscle, bone density, and racial and ethnic differences.
Definition
A flawed mathematical formula that ignores water weight, muscle mass, bone density, and racial/ethnic differences. Also, it's bullshit.
Why it matters
It stays in the book because insurers still use it as a gate. Knowing your number is useful for coverage. Believing it describes your health is not.
Also called
BMI
Source: this entry is drawn from “The Glossary” in FAT BITCH: Killing the Willpower Myth by Cat Clark (UNLIT Publishing, October 15, 2026). The full chapter has the context this page does not. Get on The First Copy List and we send the order link the day it goes live.
None of this is medical advice. It is educational material drawn from FAT BITCH: Killing the Willpower Myth by Cat Clark, and it does not replace your prescriber, your pharmacist, or your actual doctor. If something here does not match what your care team told you, go with your care team and bring this along to the conversation.