Instruct: Classify the given review into positive or negative sentiment.
Query: What's it good for?

I purchased this thing several months ago. I started taking readings 3 hours after meals. The readings are all over the place. I could take readings one after the other and each one could be from .1% to 2% difference. Did I gain all that body fat in two seconds? I don't think so. I could understand one or two tenths of a point difference but 2%? Really? And it could vary as much as 5% from one day to the next. Pure waste of money.