Junk food contains high amounts of salt, fat, sugar and other unhealthy ingredients that can negatively impact people's health. Consuming too much junk food regularly can lead to obesity, dental cavities, and increase the risk of heart disease, stroke and kidney problems. While an occasional treat is okay, junk food should not make up a large part of someone's diet and it is best to focus on eating more nutritious foods like fruits, vegetables and whole grains according to the food pyramid guidelines.