Obesity
A chronic disease characterised by an excess of body fat that harms health, classically defined by a BMI of 30 or more, though its measurement is moving towards finer criteria.
Obesity is officially recognised as a chronic disease (not simply a lack of willpower). It is classically defined by a BMI of 30 kg/m² or more, with degrees (moderate 30 to 35, severe 35 to 40, morbid >40).
An original angle (the limits of BMI): BMI is a population tool that is crude at the individual level. It does not distinguish muscle from fat: a muscular rugby player can be “obese” according to BMI. Conversely, a slim person can carry too much visceral fat (TOFI, thin outside, fat inside).
In 2025, an international commission (Lancet) proposed distinguishing:
- Clinical obesity: excess fat WITH organ or functional impairment (the true disease)
- Preclinical obesity: excess fat WITHOUT complications yet (a risk factor)
Finer measurements complement BMI: waist circumference, waist-to-hip ratio, bioimpedance.
An angle on causes: obesity is not just a simplistic “calories in/out” equation. It involves genetics, epigenetics, the microbiota, hormones (leptin, insulin, ghrelin), sleep, stress and an “obesogenic” environment (cheap, hyper-palatable ultra-processed foods, sedentary habits). Blaming individuals ignores these systemic determinants.
Ultra-processed foods play a key role: designed to be “hyper-palatable”, they short-circuit natural satiety signals and encourage passive overconsumption (you eat more without realising it).