Yan Xi, 34
Before: Yan doesn't exactly worry about looking fat, but she's "so flat-chested" that she thinks her bottom is out of proportion. This squared-off tankini top bisects her midsection, making her seem shorter and even less generously endowed.

After: A string bikini (Tomas Maier, $395) is spectacular on Yan, elongating her body, playing up her curves, and showing off slim, athletic legs.