Further to it though is your lifestyle / environment fits your weight. Fat is CRITICAL in cold environments. While being overweight with clogged arteries is bad, being thin is not always healthy either.

You can blame the proliferation of California-nuts who live in warm climates walking around half naked all day. They are some of the first to complain when it's even remotely cold.

Simple advice - If you're losing weight it's because your body is breaking it down.. because you're also not getting something it needs. It's why diets need to be fucking monitored by your doctor. You CAN get into a state where it fails to produce basic bodily fluids because it lacks nutrients, thus you get sick from simple colds / bacteria.. You have no real control over where your body gets that from. Muscles are for example ALSO consumed which can cause you to become brittle. If you're shitting once or twice a week GO SEE A DOCTOR.

There are many things that act as apatite suppressants which means you're not feeling hungry when you SHOULD BE. Red Bull for example does this to me.