Because I've stopped taking the drugs the Dr's gave me to stop the weight loss 
I understand why they are concerned - I lost 5 stone over 6 months, until they drugged me up this autumn. Before, like many overweight people, I had been trying to lose weight. When it started dropping off like magic, I was thrilled. 4 weeks and a stone lighter and I thought perhaps I should get it checked out. So I had all sorts of scans and 'scopies and such, and they found no reason at all. So they gave me two drugs to treat the symptoms: one to keep from feeling sick to my stomach when I ate (proton-pump inhibitor) and one to stop massive stomach pain when I ate 'too much' (smooth muscle relaxer). And the weight loss stopped.
I saw a gastro who gave me a stern talking to, saying that I needed to eat and if I continued to not eat, they may need to tube feed me. But it's not like I'm refusing to eat, as if I were anorexic. I have in fact been concerned that I might develop an eating disorder with this rapid weight loss, but I don't think I have. I still love food, and enjoy eating. But yes, if I start to fill ill and my stomach hurts, I stop.
But my BMI is 27, and my waist 34". Every single thing I see anywhere suggests that is not yet in a healthy range. Yes, definitely better than BMI 37 which I was before, but just because I lost a bunch of weight, does that mean I need to stop while still overweight? Had I done this on purpose, people would be telling me just a bit more, not castigating me for any further loss!
Due to a mix-up with the repeat slips, I ran out of the PPI two weeks ago. So I didn't have it for a few days, and I noticed that I felt so much better. So when I finally got it, I didn't take it again. I've been ill all winter with a series of seemingly never-ending colds, so I attributed my fatigue to that (and that I have CFS/ME, but I had been feeling considerably better since the spring, when, coincidentally - or not - I suddenly started losing weight). But I've developed two new overlapping illnesses since then, and while I feel miserable from the colds, I have noticeably more energy. I've also lost 3 pounds.
AIBU to think that it's okay to not take medication that makes me feel tired and keeps me from losing weight, when I am in fact still overweight? Surely I mustn't need to stay overweight for the rest of my life just because I had some medical issue that caused unexplained weight loss.