If the box he purchases has 6% fewer cocoa puffs in it, that is not a major concern, because he still gets six reasonably-full bowls of cereal for the same price he paid previously—and at 6% fewer calories, all other things being equal he is going to lose some weight.
A few days after eating less than usual, he becomes very hungry and eats a lot of whatever is available, even if it’s unhealthy.
He ate in a less healthy way than before the price increases.
What’s less healthy than Cocoa Puffs?