Answer: Using competing responses.
Explanation: By using low calorie diets in place of foods he would have initially gone for, Shaun is using competing responses. Here, he learns to become aware of each instance of the habit behavior (awareness) and to use a competing response alternative on the occurrence of the habit behavior or on whatever precedes the habit behavior. As a technique in behavior therapy, use of competing response involves two stages that follows: first, we identify the habit occurrence/behaviour, including root causes and warning signs; and then, we create and practice, repeatedly an alternative response to the habit behavior.