The secret to melting kilos is a strong foundation, and the best way to build muscle is with weights. "When you're doing weight training, it's not so much about burning calories; it's about gaining as much muscle as possible," explains trainer Tia Falcone. "All women need to gain as much muscle as humanly possible; that’s what’s going to make you smaller, and it raises your base metabolism permanently." Don't worry about weight training bulking you up — in fact, picking up a pair of hefty weights will actually slim you down faster than forgoing the weight room altogether.