Americans spend millions of dollars a year eating and drinking at fast food establishments. The biggest chain, in terms of sales, is McDonald’s, where people spent more than $36 billion in 2016, followed by Starbucks with nearly $15 billion, and Subway with $11 billion.

These numbers are not surprising, considering that almost 40% of people in the United States eat at a fast food restaurant at least once a day. And adults between 20 and 39 years old are most likely to choose junk food over other options.

Perhaps it’s no surprise also that the biggest health issues in the country include obesity, heart disease, cancer, and diabetes, all of which are associated with foods that are high in calories, fat, salt, and sugar.

So why is fast food so popular? It’s cheap, readily available everywhere, filling, and you don’t have to wait long for it.

Many of the least healthy items on fast food menus contain nearly the entire daily recommended intake of calories, sodium, and sugar. The estimated daily calorie need for moderately active adult men is 2,800 and 2,200 for women . The recommended daily limit for salt is 2,300 mg (ideally 1,500 mg), and that of sugar is 25 grams (six teaspoons) for women and 38 grams (nine teaspoons) for men, according to the American Heart Association.

To identify the unhealthiest food at every major fast food chain in the United States, 24/7 Wall St. reviewed the nutritional contents of every item on their menus. To compare each item, we created an index of calories, fat, cholesterol, salt, and sugar. Foods with a lot of calories, sodium, sugar, and fat relative to other items offered by the same restaurant received worse scores. Only food items intended for single individuals were considered. McDonald’s 40-piece Chicken McNuggets, for example, was excluded.

Click here to read about the unhealthiest item in every fast-food chain in the U.S.