The high fat, sugar, and salt content of many junk foods may stimulate the brain's reward system, leading to an enjoyable experience and subsequent desires for more of the same.
It's possible to build a conditioned response in the brain that drives desires if we make a practice of consuming junk food on a daily basis.
The term "emotional eating" refers to the practice of reaching for unhealthy foods when we're feeling down or bored.
Seeing other people eating junk food or being in a social setting where junk food is easily accessible might stimulate a desire for this kind of food in ourselves.
Marketing and promotion help make junk food more appealing, which in turn increases the desire for it and hence the consumption of it.
Reasonable accessibility: When we're pressed for time or don't have access to healthy choices, junk food may be a quick and simple solution.
Some individuals may become dependent on unhealthy foods, suffering intense cravings and withdrawal while attempting to cut down or stop.
The evolutionary biology of food cravings explains why we sometimes feel an overwhelming want to eat high-calorie, high-fat, high-sugar junk food.