Women store more fat than men to protect their vital organs so no matter how small or lean you are trying to get, there will always be body fat around the belly. Having said that, strengthening the pelvic floor through Pilates and core workouts will help to tighten the stomach muscles and hopefully leave you with a more toned abdomen. Couple this with strength and resistance training, which is commonly ignored by women, and you should be onto a winning formula.
