TOFI (thin outside, fat inside) is a state where weight and BMI are normal, but the share of fat, especially visceral fat, is elevated. Such people are described as "metabolically obese at a normal weight".
Outwardly the person is slim, but metabolically they are closer to people with obesity.
Why a normal weight is misleading
BMI accounts only for weight and height and does not distinguish fat from muscle. You can have a normal BMI but excess visceral fat, fat in the liver (steatosis) and little muscle. It is estimated that up to ~29% of people with a normal BMI have a body-fat share in the "obese" range.
Why it is dangerous
Visceral fat raises insulin resistance, sustains chronic inflammation and increases the risk of type 2 diabetes and cardiovascular disease — almost as much as overt obesity.
How to detect it
BMI is not enough. Look at body-fat percentage, waist circumference and the waist-to-height ratio, and body composition (bioimpedance, DEXA). A large waist and poor lab results at a "normal" weight should raise a flag.
Calculate using this marker
Calculators where TOFI (normal-weight obesity) is used directly:
Frequently asked questions
Can you be thin but obese?
Yes — that is exactly TOFI. At a normal weight you can have excess visceral fat, insulin resistance and poor lab results. Outward slimness does not guarantee metabolic health.
How do I know if I have TOFI?
Assess more than just weight: measure your waist and waist-to-height ratio, check body-fat percentage and body composition, and test glucose, HbA1c and lipids. A large waist and poor labs at a normal BMI are a reason to suspect TOFI.
Related terms
Sources
- Thomas EL et al. / TOFI phenotype and its effect on the occurrence of diabetes. PubMed, 2017
- TOFI (thin outside, fat inside) — overview