In general "much" is actually neutral. It depends on the context whether it is negative or positive.
Positive: We had so much fun. There were so much good food at the party. I have so much money now.
Negative: I have so much work to do. I ate too much. I don't have much money left.
"Too" on the other hand, often take a negative meaning (though not always).
So I would rather say: You are eating TOO much sugar these days .
I hope my explanation helps :)