Avoid dresses that accumulates on your waistline. It does not mean that you have to wear dresses that draws attention on your waist, rather opt for dresses that focuses your curves without leading to much focus on your waist.
If we go with flatter, cleaner design for the actual app, let's remember how that should coordinate to stats and infographics later. (Partially you guys, partially Dallas team.) Flat Elements for Infographic Design