Metamucil Weight Loss Blog Metamucil is a dietary fiber which bulks up in the stomach to produce a full feeling. By taking Metamucil before eating you will eat less and will lose weight easily. in Public bookmarkswith best_dietlose_weightmetamucil_weight_loss Note: Metamucil is a dietary fiber which bulks up in the stomach to produce a full feeling. By taking Metamucil before eating you will eat less and will lose weight easily.