Potatoes are commonly eaten baked, boiled, mashed, and fried. Relative to the other three preparation methods, frying results in a lower glycemic index, higher calorie density, greater palatability, and lower satiety per calorie.[1][2] This is likely to increase calorie intake and contribute to weight gain. Consistent with this, an observational study reported that people who increase their intake of French fries and potato chips experienced much more weight gain than people who increased their intake of baked, boiled, or mashed potatoes.[3] This must be interpreted with some caution due to the possibility of confounding by other diet and lifestyle factors. Adding calorie-dense toppings or ingredients like butter and cheese to baked, boiled, and mashed potatoes is expected to make them less filling per calorie.
Cooling potatoes after cooking tends to reduce their glycemic index and insulin index, even if they are subsequently reheated, although this is not always the case.[4][5] To the extent that dietary glycemic index and insulin index may impact health, cooling potatoes prior to eating may make them healthier.
High-temperature cooking of some foods creates a carcinogen called acrylamide, and fried potatoes are one of the largest dietary exposures to this compound.[6] Although dietary acrylamide is a theoretical concern, observational studies have not reported consistent links between dietary acrylamide intake and the risk of cancer at any site, with the possible exception of kidney cancer.[7] Soaking potatoes prior to frying reduces the formation of acrylamide.