It's just leveraging the information you have on the user. That's what marketing companies do all day long. Bidding for ad spots in the marketplace and putting the right product at the right time in front of your eyes. Putting the ad of a local restaurant in front of a hungry man will result in more clicks than if the man is not as hungry, and more clicks than putting a pair of shoes.

You can probably also up sell your products if you detect your customer is not playing his A-game. A hungry mind will typically explore less options and be more prone to risky behavior. It's probably something inherited from thousands of years of evolution, when you are hungry and there is a potential reward you take more chances, you don't think and you go get it.