Getting a flatter belly, thinner thighs, and a tighter tush is a two-part process. Step one is mastering the moves in our Summer SHAPE Up on page 4, but if you don’t also revamp what you eat, those newly cut muscles will stay hidden under a layer of fat. Enter this personalized program, designed by Jackie Newgent, R.D., author of 1,000 Low-Calorie Recipes. Replete with tasty, satisfying foods, it’s tailored to your needs (gluten-free, for example, or vegetarian) and lifestyle (gourmet cook versus on-the-go eater)—both key to sticking with the regimen and seeing long-term results. Consume about 1,600 calories a day following one of the meal plans below and you’ll be ready to debut a new bikini by Memorial Day. Keep going for three months (we’ll provide more options in…