The combustion of carbohydrates and the combustion of fats are both exothermic processes, yet the combustion of carbohydrates is a faster process. How can this be?

There are two aspects of a reaction:

Thermodynamics:

Combustion of the compound is reaction with oxygen.

The carbohydrates contain more content of oxygen as compared to fats.

Hence, carbohydrates have lot of oxygen content which are already partially oxidized as compared to fats. Hence, combustion of the carbohydrates is a faster process.

Kinetics:

The molecular reacts also shows that the combustion of the carbohydrates is a faster process.