Gaining

If by weight gain shakes you mean protein shakes then it depends on what your goals are. They can add calories to your diet, yes, but since they are largely protein it won't trigger the same response as say a chocolate milkshake. The carbohydrates/sugar in a regular milkshake would spike your blood sugar and trigger an insulin response, which in turn would store more fat per calorie then if it was all coming from protein. This does lead to a higher risk of diabetes and other complications however. A protein shake on the other hand would simply increase the volume of calories which would cause weight gain as well, but at a much more reduced rate.


tl;dr

Protein (weight gain) shakes: Healthier slow gain.

Regular sugary shakes: faster gain but with more risks for health complications later on if you don't plan on eating a protein based diet.

I used to work out a lot in HS, so here is the deal on shakes.

Protein shakes (whey, casein, soy ...) Are good for building muscle, but have fairly to very low actual calories. A scoop of whey is like 80 calories, because its all protein. Actually they can help you lose weight, because the protein helps lower carb cravings. essentially you need the protien to put on lean mass (muscle), but its not for bulk (fat ... jiggle)


weight gain shakes, are pretty much all carbs and fat. They have VERY high amount of calories, because they are meant for bulk. basically if you are a really skinny guy, and you work out like CRAZY... and + lots of protein.. You could put on muscle + bulk. You never can put on muscle alone, when you gain mass its always some fat some muscle. The hardcore body builders gain mass, then lean down afterwards. You can put on muscle just working out + protein, but its going to be slow.

Now the part relevant to your question, weight gain shakes are pretty much nothing but calories. If you are a girl, or a guy not working out, your going to put on practically all fat. So yes they 100% work, I never used them but my good friend did. he worked out hard, and still put on a lot of fat. Its simple science really, take in more calories than you burn daily and you gain. If your not working out, ESPECIALLY if your a girl, its pretty much all jiggly fat. Gain shakes can have around 700-1300 calories a serving. They don't taste that good, but they will help you gain FAST.