My guess: It appears as though your reason for posting was to say "I could never do that on a carb based diet". However, you never established and reason for that conclusion. Each of us has our personal opinion on a variety of different subjects. We could all post that personal opinion without any corroborating evidence, but because there are a lot of people, this would create a comment section containing mostly noise. People would prefer to see comments based on research or personal experience that seems to strongly corroborate the conclusion. Generally it has been my experience that I do not get many down votes simply because people disagree or are unhappy with what I'm saying. It's usually because I am clearly wrong, or I have simply contributed to the noise.

I think that your comment falls into the noise category and is undesirable because of that. If you had explained personal experiences to show how you reached your conclusion, It think you would get a better reaction. If you also showed how other possibilities could be rules out, then I think people would find it very interesting and you would get many up votes.