There are pros and cons in frying food.
The dietary fiber in potatoes raises while frying. With frying happening over a short time because of the high temperatures, less vitamins leach when compared to alternative cooking methods. Fried foods are however fattening because of the high calories. One other issue is cooking oils that are unstable may go rancid as well as oxide at high temperatures.
The infographic by AuthorityDiet.com goes through in detail how to choose your cooking and frying oil. Choose your cooking oils diligently if you wish to gain the pros and avoid the cons of frying food.