Years ago my grandmother, who had long been the same size, began a diet program and walking. She lost weight, but was not close to being too "thin". Some people came in with cautioning her, as if she was causing herself harm. And they told her she lost too much weight and didn't look good. It was so intrusive, out of line and rude. She was feeling good and doing something for herself. She had accomplished so much.
There are so many underlying mentalities and disconnected people feel free to tell you what they think about your body.