Junk food contains large amounts of fat, and as fat accumulates in your body, you'll gain weight and could become obese. The more weight you gain, the more you'll be at risk for serious chronic illnesses such as diabetes, heart disease and arthritis. You could even have a heart attack.
The high levels of fat and sodium in junk food can cause high blood pressure or hypertension. Excessive dietary sodium can also have a negative effect on renal function, even leading to kidney disease.