The other three chains are Nando's, Subway and Wimpy. All have promised to work towards reducing salt and saturated fat levels in their best-selling products, swap sauces, dressings and oils for alternatives that are lower in saturated fat, and add more healthy options to their menus.
Restaurants will also make it easier to find nutritional information.
The aim of the commitment is to help the Food Standards Agency's activity to get people to eat more healthily when they're not dining at home.
It follows moves by supermarkets to cut the amount of salt, sugar and saturated fats in the ready meals that they sell.
Rosemary Hignett, head of nutrition at the FSA, said: "Eating out should be fun and we don't want to change that, but we believe restaurants can help make it easier for us to take healthier choices when dining out.
"These companies' commitments, together with the positive work that many have been doing for a number of years, show just how much is possible.
"We hope that other restaurant chains will be able to emulate this exciting work."
The FSA is also working closely with the largest pub, family restaurant and coffee shop chains, to develop similar commitments.
It is reacting to concerns that more people are becoming obese and fears that this will put a huge strain on the National Health Service.