Can strength training help you lose weight?
An exercise like sit-ups or abdominal crunches uses a much smaller volume of muscle than whole-body aerobic exercise and is therefore less efficient at burning calories than an exercise like jogging. Instead, high weight/low rep exercises can be used to maintain or increase the body's muscle mass while dieting. This helps to prevent the metabolic slowdown that otherwise often limits the effect of dieting and causes post-diet weight gain.
This too depends on the type of strength training utilized. Because weight training generally is used for bulking, this type of exercise more than likely will increase weight because of the muscle gain. However, when resistance or circuit training is used, because it is not geared towards bulking, women tend to lose weight more quickly.
Because most strength training builds lean muscle, it is natural for a person to gain weight, initially, since muscle is heavier than fat. However, as lean muscle is built, as a result, the weight will begin to regulate and decrease. Lean muscle helps raise the metabolism which helps keep weight down.
Information from: wikipedia