Maybe the one size fits all isn't such a good idea.  This is so spandexy that it is very tight, which usually I don't care about because you wear it underneath of stuff..I usually prefer them snug.  This is very snug, it is still comfortable, but unless the shirt you have on top is loose, it can give you a little bit of an unflattering muffin-top look, but on top!  It will show your back fat on top and below this.  It also slips down over time, so doesn't give you a lot of coverage.  wish it could fit higher. Better than nothing, but not the best.  I have several colors too.  If you are smaller with no backfat, it might be fine.