I dunno about you but some days I wake up larger. It could be the time of the month or an excess of goodness knows what. Therefore on such days I turn to shapewear. Usually a M&S big knicker number but for dresses you need a good all over number to deal with ones growing pains.
The crème de la crème has to be Agent Provocateur's Zelma satin contour dress £425 from Net-A-Porter. So good you'd probably take a punt on wearing it out on its own!
For one that does the job with no fancy pants details, then the Wolford Individual Nature Forming Dress £75 from Net-A-Porter is the perfect cover all.
Good old ASOS sells the Flexees Firm Control Full Slip £36 which performs the job of slimming down stomach, thighs, muffin tops and wait for it...back fat.