One rarely accesses stored body fat during exercise, regardless of the intensity, time of day, etc. Most of the triglycerides utilized during exercise are stored in the muscle. It does not prevent the utilization of triglycerides during exercise.
Exercise actually causes insulin levels to decrease.
The body's hormonal responses to exercise are complex and dynamic and cannot be described in simplistic and absolutist terms. It is physiologically impossible to exercise without utilizing glycogen. It is also impossible to somehow trick the body into using a specific energy pathway.