The most harmful food to eat is fast food.
When you eat fast food on a regular basis such as Mcdonald hamnurgers, fries etc or other fat food joints food then that can be harmful.
Fast food is cooked in a lot of grease and fats and contains artificial ingredients.
Even eating too many hamburgers, bacon etc at home or too much other deep fried food at home can be harmful to your health.
The fast food including home cooked deep fried food can increase your weight and also clog your arteries which can lead to heart attacks, heart disease, strokes etc.
Eating too much butter is also harmful to your health.
Although it's okay to eat fast food and deep fried food in moderation but you should eat other healthy foods such as vegetables, fruits etc.
I eat fast food once in awhile but I do my best to eat healthy food that I prepare at home.