If you don't regularly train with weights you WILL have body flab. It's as simple as that. The appearance of body flab results when you are generally sedentary (inactive) or if you lose a significant amount of weight with dieting and/or excessive amounts of cardio exercise.
Dieting and cardio lead to reductions in body water, fat, and muscle. Since muscle partly contributes to the body’s shape and form, any loss in muscle will result in excessive flab around your body. By building and/or maintaining your muscle with weight training during and after weight loss, you can counter the appearance of body flab.
