Answer:
Potato chip
Explanation:
There were studies about what is the lets say universal food, on which you would live the longest. Sorry, for not being able to find that source, but it stated that the two ingredients were potato and butter.
Now potato chips are mostly composed of carbs and fats. Therefore, it would take time to burn up, especially the fat, since it is being burnt down the longest.
So there you go. The answer is: potato chip