Bella Hadid's nutritionist has revealed the diet the model sticks to in order to maintain her catwalk ready figure.

To be in the best possible shape for the runway, the 21-year-old star sticks to a high protein low carbohydrate diet which includes lots of lean meat and fish, non-starchy vegetables and foods packed with healthy fats such as nuts and avocado.

Speaking to PEOPLE, Dr. Charles Passler said: ''It's adequate protein, adequate fat, and lots and lots and lots of non-starchy vegetables. That is typically the most bulletproof, easiest, soundproof way to make sure that somebody stays on track.

''If you eat a lot of carbohydrates, with your protein and your fat, the body's going to use the carbohydrates for fuel first.''

''The body loves using carbs for fuel. So the body's going to soak up all of those carbs, and if then you don't need any more fuel, the body's going to just turn the extra calories from the fat and the protein into body fat. So by eliminating the carbohydrates, and consuming the protein and the fat, it not only keeps your calories down, but it keeps your energy stable.''

Dr. Passler insists the only way to maintain a healthy balance in your body like Bella - whose older sister is fellow model Gigi Hadid - is to change your lifestyle to make healthier choices.

He said: ''It's really about accepting a reality that it's time to change your lifestyle. You're just a person that does not drink soda - I don't care if you're at a birthday party, and that's all they have, then don't drink anything. I don't care if you're the person that loves pizza, well, just minimise the pizza intake, or minimise the refined sugar intake.

''In order for somebody to be consistently healthy, the biggest key is to engage in a lifestyle that allows you to own that permanently.''