You know how they say you should never go grocery shopping when you're hungry?
Well, it might have something to do with how hunger heightens your sensitivity for saltiness and sweetness.
Neuroscientists tested people's abilities to taste salty, sweet, and bitter solutions both after a fast and after eating a meal. The participants ate a prescribed meal for dinner, and then they were tested the next day after not having any breakfast. They were tested a second time after eating lunch. The results showed that people can detect lower concentrations of saltiness and sweetness when they're hungry than when they're satiated. However, our ability to detect bitterness remains constant.
Sweetness and saltiness signal that a food is edible, and so it seems to make sense that when our bodies need energy, we would be more sensitive to these tastes. Bitterness, on the other hand, can signal that a food is unsuitable, possibly toxic. Hence, it may be to our benefit to be highly sensitive to bitterness whether we're hungry or not.
Some scientists think that when food was more scarce it made sense to be attracted to fatty foods, so as to store fat reserves. That we're still attracted to these foods may go to show that our genes have yet to adapt to the changes in our environment.