Gordo vs. obeso
The Spanish words gordo and obeso both refer to having excess body fat, but they differ significantly in tone, context, and severity. While gordo is an everyday, versatile word, obeso is a formal, clinical term.
Gordo
The word gordo is the most common, everyday term used to describe someone or something as fat, plump, or chubby, and it can even be used as an affectionate nickname or to describe thick objects.
Mi gato está muy gordo porque come todo el día.
(My cat is very fat because he eats all day.)
Cuando era pequeña era un poco gorda, pero luego adelgazó.
(When she was little she was a bit plump, but then she lost weight.)
Ven aquí y dame un abrazo, mi gordo hermoso.
(Come here and give me a hug, my beautiful chubby boy.)
El profesor nos pidió que leyéramos un libro muy gordo para el viernes.
(The teacher asked us to read a very thick book for Friday.)
Él sabe que está gordo y quiere empezar a ir al gimnasio.
(He knows he is overweight and wants to start going to the gym.)
Obeso
The word obeso is a formal, medical term used to describe a living being that is clinically obese, meaning they have a dangerously high amount of excess body fat that impacts their health.
El médico le advirtió que si no cambiaba su dieta se volvería obeso.
(The doctor warned him that if he did not change his diet he would become obese.)
El programa de salud está diseñado para ayudar a niños obesos.
(The health program is designed to help obese children.)
Un paciente obeso tiene un mayor riesgo de desarrollar diabetes.
(An obese patient has a higher risk of developing diabetes.)
Llevaron al perro al veterinario porque estaba clínicamente obeso.
(They took the dog to the vet because he was clinically obese.)
Es importante distinguir entre alguien que tiene un ligero sobrepeso y alguien que es obeso.
(It is important to distinguish between someone who is slightly overweight and someone who is obese.)
Summary
In summary, use gordo for casual, everyday descriptions of fatness, plumpness, thick objects, or as a term of endearment. Reserve obeso for formal, health-related contexts to describe the specific medical condition of being obese.