It's pretty easy to stay low carb at chipotle since most of the ingredients are keto friendly. You're going to have to stay away from the wraps, rice, and beans thought. Chipotle even offers a handy nutrition calculator.
Start with a bowl filled with lettuce. Then you can add any of the meats that you want: chicken, steak, carnitas, barbacoa, sofritas. No rice or beans but you can add fijata vegetables if you would like. They are an additional 5 carbs. Any of the following are also acceptable: queso, fresh tomato salsa, tomatillo green chili salsa, tomatillo red chili salsa, sour cream and/or cheese. Guacamole is a litter bit on the higher side with 8 carbs per serving.
John Ward has been experimenting with low carbohydrate diets since the early 2000s. He successfully used a low carb diet to lose 50lbs in the past and currently follows a keto diet for a variety of reasons including general health and managing mood levels.