Or that extra foods puts more stress on your organs. Liver, kidneys, pancrease, etc have to do more work and for some reason the body isn't able to repair that and they wear out quicker.
What is problematic however is that after some time, there is a built up of errors in the dna. If those errors do not get corrected, that is when you see a decline in organ quality, what we call aging.
If interested, see my other posts for more pointers.