Junk foods are often high in fat, sugar, salt, and calories which are not good for the health. Here is an article about" Reasons Eating Junk Food Is Not Good". It states that eating too much junk food will lead to obesity, diabetes, depression, nutrient deficiencies and high sodium levels.
http://healthyeating.sfgate.com/reasons-eating-junk-food-not-good-3364.html