CalorieLab states that there are 42 calories in 1 cup of grilled, sliced portabella mushrooms. On the other hand, 1 cup of sliced, stir-fried white mushrooms has 28.1 calories.
According to CalorieLab, raw mushrooms do not necessarily have a lower calorie count than cooked mushrooms. However, canned mushrooms generally have a higher calorie count per cup than other types of mushrooms. The World's Healthiest Foods lists a number of proven health benefits from mushrooms. For example, it has been found that extracts from crimine, maitake, shiikate and white button mushrooms reduce the binding of particular immune cells, protecting against cardiovascular disease by reducing the risk of problematic blood flow and aorta damage.