A one-kilogram mass is still a one-kilogram mass (as mass is an extrinsic property of the object) but the downward force due to gravity, and therefore its weight, is only one-sixth of what the object would have on Earth. So a man of mass 180 pounds weighs only about 30 pounds-force when visiting the Moon.
Like all fruit, apples contain fructose, and too much of this sugar at a time provides your intestinal bacteria with a substrate in which to ferment, which leads to gas production, bloating and abdominal pain. Apples are a healthy addition to any diet, but too many can lead to digestive issues.
The A in the BRAT diet, apples are also a good source of pectin. However, the high fiber in raw apples makes them too rough for a dicey intestinal system. Cooking the apples makes them easier on your system to digest. This allows you to benefit from the pectin and the other nutrients that apples have to offer.