Junk food plays a major role in the obesity epidemic. By the year 2050, the rate of obesity in the U.S. is expected to reach 42 percent, according to researchers at Harvard University. Children who eat fast food as a regular part of their diets consume more fat, carbohydrates and processed sugar and less fiber than those who do not eat fast food regularly. Junk food in these children's diets accounts for 187 extra calories per day, leading to 6 additional pounds of weight gain per year. Obesity increases your risk for cardiovascular disease, diabetes and many other chronic health conditions.DiabetesYour insulin levels become elevated when you eat processed sugars, such as those in soft drinks, white flour and other foods devoid of fiber and nutrients necessary to properly metabolize carbohydrates. Eating junk foods throughout the day causes chronically high insulin levels, which eventually prompts your cells to begin to ignore this important hormone, resulting in a condition known as insulin resistance. Ultimately, obesity and Type 2 diabetes may set in. Since the 1980s, Type 2 diabetes, which was minimal in teenagers, has risen to 15 percent.DepressionJunk food may lead to depression in teenagers, according to Andrew F. Smith, author of the book "Fast Food and Junk Food: An Encyclopedia of What We Love to Eat." Hormonal changes at puberty make teens more susceptible to mood and behavioral swings. A healthy diet plays a part in keeping hormone levels on an even keel, while a diet high in junk food falls short of these requirements. Consuming trans fats, saturated fats and processed food is associated with up to 58 percent increase in risk of depression.Nutrient DeficienciesProcessing that removes vitamins, minerals and fiber makes junk foods into the sources of empty calories that nutritionists disparage. Children who eat a lot of junk foods may develop nutritional deficiencies that lead to low energy, mood swings, sleep disturbance and poor academic achievement, among other health conditions, according to the University of New Hampshire Cooperative Extension.SodiumHigh sodium levels are a defining characteristic of many junk foods and one of the contributing factors to the overconsumption of salt that typifies the Western diet and contributes to high blood pressure and heart, liver and kidney diseases, according to Harvard Health Publications. The average American eats five to 10 times more salt than the 2,300 milligrams per day recommended by the U.S. Dietary Guidelines for Americans. Considering the high rates of high blood pressure among Americans, that level should be even lower -- about 1,500 milligrams per day -- for 70 percent of adults. However, the trend since 1988 shows that fewer people with hypertension adhere to a low-sodium diet now than did then.