Animals typically digest their food in an internal cavity and store reserve food energy primarily in the form of:
Unlike plants which store excess photosynthetic energy mostly as starch, the metabolic systems of animals are vastly different. According to the NCERT Biological Classification chapter, members of Kingdom Animalia directly store their reserve food energy primarily as 'glycogen or fat'. These highly efficient energy storage molecules can be rapidly mobilized during locomotion or starvation periods.
Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.5 Kingdom Animalia