BMI is reasonably accurate as a population-level screening tool, but it's a blunt instrument for any individual — because it only uses height and weight, it can't tell muscle from fat. That's the honest answer: useful as a rough flag, unreliable as a personal verdict. Here's the nuance.
What BMI actually is
BMI (body mass index) divides your weight by your height squared to put you in a category: under 18.5 (underweight), 18.5–24.9 (healthy), 25–29.9 (overweight), 30+ (obese). It's quick, free and decent for spotting trends across large groups.
Where it misleads individuals
Because it ignores body composition:
- A muscular person (athlete, regular lifter) can register "overweight" or "obese" despite low body fat — muscle is dense (does muscle weigh more than fat).
- A "healthy BMI" person can carry high body fat and low muscle ("skinny fat").
- It says nothing about where fat sits, which matters for health.
So as a personal health verdict, BMI alone is weak.
Better measures for an individual
- Waist measurement / waist-to-height ratio — a better signal of harmful fat.
- Progress photos and how clothes fit.
- Body-fat estimates (calipers, scans) if you want detail.
- The weekly weight trend alongside these, not BMI in isolation.
The forme view
This is the same theme as the rest of nutrition: a single universal number rarely captures you. Your goals and body composition matter more than one category (is this food good for me, personalised nutrition).
Goals that fit you, not a category
forme builds your targets and food score around your own goals and body — not a one-size-fits-all number like BMI.
The bottom line
BMI is a handy rough screen but a poor individual verdict — it can't separate muscle from fat. Pair it with waist measurement, photos and the weight trend for a truer picture. This is general information, not medical advice — speak to a doctor about your individual health.