Any truth to this statement? My dad's oncologist saw me for the first time in 2 weeks today and he said, "You've lost a lot of weight." He initially asked because he thought I wasn't eating because of stress, then I explained to him that I was purposely losing weight with diet + exercise. He asked me how much weight I've lost and I told him I've lost 16lb in 6 weeks or so. He told me that losing weight too fast will make it harder to keep off. I'm not particularly worried because my diet was a lifestyle change, but I was wondering if what he said is true.