more than average fatness
"The doctor warned that his obesity posed serious health risks due to carrying significantly more body fat than is typical for someone of his age and height."
The state of being obese due to an excess of body fat.
"His recent weight gain was diagnosed as obesity caused by a significant increase in body fat rather than muscle mass."
In plain English: Obesity is when someone has too much body fat that affects their health.
"The study examined how childhood obesity affects long-term health outcomes."
Usage: Obesity refers specifically to the medical condition caused by excessive body fat, distinguishing it from general weight gain or overweight status which may involve muscle mass. Use this term when discussing clinical diagnoses and health risks associated with high levels of adipose tissue rather than casual descriptions of size.
The word obesity entered English from the French obésité, which ultimately traces back to the Latin obēsus meaning "fat." Although it appears to be a modern combination of obese and -ity, its roots lie in ancient descriptions of being overweight.