The most common problem in gaining muscle and strength is not the lack of protein but the lack of calories. It is a well documented fact that muscle growth will only happen if, and only if there are sufficient of calories to support the muscular growth. If the body does not have enough calories (ie. caloric restriction), it will get the energy it needs by protein degradation, thus converting amino acids into glucose for energy. Unfortunately, energy requirements will always take priority over tissue anabolic reactions (tissue building).
Any aerobic exercise in addition to the already restricted caloric intake will even further increase the rate of protein degradation. This means that you WILL lose lean body mass regardless of the amount of dietary protein consumed from a calorie deficient diet.
Bottom line...if you want to gain mass and strength, you MUST EAT. Of course this means that the body fat percent may have to be sacrificed a little. Don't let anybody kid you, the more body weight you have, the stronger you will get. The stronger you get the more muscle mass you will have.
Most athletes have a real problem in the calorie department because they only think they are eating enough calories. There are many reasons why most athletes are not eating enough calories to support muscular growth: meal times are rushed, skipped meals, food is not readily available at times of hunger, lack of appetite when large amounts of calories are needed, tired of eating all the time, and the list goes on. Weight gainers will provide more calories than most would eat at a normal meal or snack thus, solving many of these problems. They are convenient and quick. Weight gainers can give a strength athlete the extra nutritional calories needed to promote muscle growth. The primary purpose of a weight gainer is to serve as a source of calories, so if you are not getting what you need at meal time, why not supplement the rest?
Weight gainers CAN NOT take the place of a hard strength training program or an adequate diet, but they CAN boost the caloric intake and, in doing so, greatly aid the athlete's efforts to gain strength and muscle.