Well, actually, 1) She brought up potatos merely because someone else brought up an argument about potatos. She ate many other things. RTFA. 2) Calories aren'

Well, actually, 1) She brought up potatos merely because someone else brought up an argument about potatos. She ate many other things. RTFA. 2) Calories aren't everything. Nutrients matter. Potatos are actually cheaper than rice when you account for all the nutrition. So it would make sense to make potatos a significant part of your diet, while still also mixing in plenty of rice (and, crucially, beans). If you actually ate nothing but rice you would become nutrient deficient and become sick.