The term junk food refers to foods high in calories, unhealthy fats, sugar and salt but low in valuable nutrients like complex carbohydrates, protein, vitamins and minerals. Snacks and dessert foods like candy, potato chips and ice cream, as well as fast foods like hamburgers and french fries, all fall into this category. While the occasional junk food meal won't ruin your health, consistently eating junk food contributes to serious health problems.
Although junk food satisfies your hunger, it provides little nutrition. Continually snacking on nutrient-poor foods can leave you with too little appetite for more nutritious foods, increasing your risk of nutritional deficiencies. The average American diet is deficient in fiber, omega-3 fats, magnesium and calcium, writes Dr. Steven Masley on ClinicalAdvisor.com. Highly processed foods contain little fiber, a substance your body needs for a healthy gastrointestinal tract and for control of cholesterol and blood sugar levels. Vegetables, fruits and whole grains are the main sources of fiber, as well as many other essential nutrients.
Natural whole foods like vegetables, whole grain products and lean meat typically contain fewer calories by volume than junk foods like french fries, donuts and hamburgers. For example, a 100 g serving of plain baked potato provides 93 calories compared to 292 calories in 100 g of restaurant french fries, according to the USDA Nutrient Database. By eating 500 calories a day more than you need, you'll gain about a pound each week. Because fast foods are so high in calories, frequenting fast food restaurants increases your risk of unhealthy weight gain and insulin resistance, which in turn raises your diabetes risk, explains Dr. Lily Strong with the University of Michigan.
Your body needs some fat for health, but junk food provides primarily fats that harm your health. Foods like hamburgers, pizza, ice cream and potato chips contain large amounts of saturated fat and cholesterol, which in excess may put you at risk for heart disease. Trans fats, too, can raise heart disease risk. These man-made, processed fats are common in commercial baked goods, such as cookies and crackers, along with potato chips and microwave popcorn. Processed, packaged foods are often high in salt, or sodium. Excess sodium in your diet can increase your risk of high blood pressure and stroke.
A diet that provides large amounts of processed carbohydrates like those in candy, commercial baked goods and potato chips promotes insulin resistance. In insulin resistance, some cells no longer respond to insulin, which leads to high blood sugar, increasing risk of diabetes. High-glycemic-index foods, which cause a rapid rise in blood sugar levels, promote diabetes and heart disease. High-glycemic-index junk foods include potato products, hard candy, sugary breakfast cereals and white flour products such as donuts and cookies.