diet
n. C / Un. the specific types of food and drink that a person or animal usually consumes. It can also mean a plan where you eat less to lose weight.
n. the habitual nourishment of an organism; alternatively, a regulated course of eating and drinking for medical or weight-loss purposes.
A healthy diet includes plenty of fresh vegetables.
The doctor recommended a low-salt diet to help manage his high blood pressure.
While the traditional Mediterranean diet is celebrated for its cardiovascular benefits, modern urban lifestyles have increasingly shifted toward processed foods high in refined sugars.
Countable when referring to a specific weight-loss plan or a particular culture's eating habits; uncountable when referring to the general concept of food consumption.
I am in a dietI am on a dietThe preposition 'on' is used with 'diet' when referring to a weight-loss plan.