The calorie counts listed on products we buy in the grocery store have limited use as some foods are less digestable than others:

If the plant material we eat has more of its cell walls broken down we get more calories from it. In some plants, cooking ruptures most cell walls; in others, such as cassava, cell walls hold strong and hoard their precious calories in such a way that many of them pass through our bodies intact.

It is not just cooked vegetables though. Nuts flagrantly do their own thing, which might be expected given that nuts are really seeds whose mothers are invested in having them escape digestion. Peanuts, pistachios and almonds all seem to be less completely digested than their levels of protein, fat, carbohydrates and fiber would suggest. How much? Just this month, a new study by Janet Novotny and colleagues at the USDA found that when the “average” person eats almonds she receives just 128 calories per serving rather than the 170 calories “on the label.”

Read more here.