Collocations for diet - noun

good, healthful (AmE), healthy, nutritious, sensible
balanced, varied, well-balanced
adequate
People can fight infection more easily if they have an adequate diet.

bad, poor, unhealthy
staple
a staple diet of cornmeal and vegetables

daily
vegan, vegetarian
American, Mediterranean, Western, etc.

consume, eat, have
It is important to eat a balanced diet.

live on, survive on
They had to survive on a diet of insects and berries.

feed sb, feed sb on, keep sb on
change
She was told to change her diet and quit smoking.

supplement

consist of sth, contain sth
The animal's diet consists mainly of grasses.

in a/the diet
the amount of fat in your diet

on a diet
These animals live on a mainly vegetarian diet.

diet of
They were fed on a diet of rice and vegetables.

a diet high in sth, a diet rich in sth
a diet rich in vitamins and minerals

strict
weight-loss, weight-reducing
crash, starvation
Crash diets are not the best way to lose weight.

fad
calorie-controlled (esp. BrE), low-calorie (esp. AmE)
restricted, special
dairy-free, gluten-free, etc.
high-fibre/high-fiber, high-protein, etc.
low-carb, low-fat, etc.

follow, have
If you follow this diet, you're bound to lose weight.

go on, start
stick to
I have to stick to a low-fat diet.

be on
I'd love a dessert, but I'm on a diet.

drink, food
Coke™, soda (esp. AmE)
pill
plan
Lose pounds with our new diet plan!

book

on a diet
athletes on a special high-protein diet