There are only 70 calories and just 0.01 grams of fat in 100 grams of potatoes. The tuber only becomes a calorie bomb when it is prepared with a lot of oil or fat.
Fries fried in oil are of course higher in calories than cooked jacket potatoes. To make potatoes healthier, there is a useful trick: eat potatoes warmed up from the day before. When it cools, the structure of the starch changes and what is known as resistant starch is created. This cannot be digested by the small intestine and ends up in the large intestine.