Illustration of a mass gainer supplement for skinny guys.

Mass gainers, also known as weight gainers, are a common supplement that people use to help them gain weight, build muscle, and bulk up. They’re especially popular among so-called “hardgainers“—skinny guys who are having trouble eating enough calories to gain weight. I’m a naturally skinny guy myself, and over the course of gaining 65 pounds, that was always my biggest issue. As a result, I’ve experimented with my fair share of mass gainer shakes.

So, do mass gainers work? Are they healthy? Do they cause excess fat gain? And, if you’re a skinny guy who’s struggling to gain weight, should you use them?

Bony to Beastly illustration showing a skinny guy bulking up and becoming muscular.

What Are Mass Gainers?

Mass gainers, sometimes referred to as weight gainers, are high-calorie shakes. The best ones are moderately high in protein, containing at least 27 grains of protein per serving, and often as much as 50 grams. But the bulk of the calories should come from easily digested starchy carbs, such as maltodextrin. A typical serving, then, might contain 50 grams of protein and 250 grams of carbs, yielding 1200 calories overall… which is quite a lot!

Illustration of a mass gainer / weight gainer supplement.

There are a wide variety of mass gainers containing a variety of different ingredients. Some mix together whey with casein and egg protein. Others use ground up oats instead of maltodextrin, driving the fibre content higher. Some include fats in the mix. Most of them use the same general format, though: enough protein + tons of starchy carbs. And that’s usually a good thing.

Do Mass Gainers Work?

Yes, mass gainers work. They contain tons of easily digested calories, and those calories come from the sources that are best for building muscle: protein and starchy carbs. They also keep the fat content low, minimizing the potential for those specific calories to be converted into body fat. (Although if you’re in an overly large calorie surplus, the other calories you’re eating will still be converted into body fat.)

A graph showing the muscle growth and fat gains from a hypertrophy study.

For example, in this study, men supplementing with maltodextrin and whey protein were able to gain 7.5 pounds of muscle over the course of 8 weeks while simultaneously losing a tiny bit of fat. These are some of the better results seen in hypertrophy studies, and much of it likely comes down to the workout program the researchers used, but even so, it shows that a mass gainer can be a good part of a bulking plan.

27–50 grams of protein is enough to fully spike muscle protein synthesis, depending on the source. If your mass gainer contains whey protein, even 27 grams of protein is enough. Most mass gainers contain far more protein than that, and whey protein is the most common source. Oftentimes it’s whey protein concentrate, and that’s perfectly fine. The only reason you’d want a blend of protein sources is if you’re getting a lot of your calories from whey already, and you want to avoid having so much of it that you get diarrhea (which is a good sign that you’re overdoing it on the whey protein).

The carbohydrate source is often maltodextrin, and that’s fantastic—maltodextrin is brilliant for building muscle. It’s quickly digested, easily absorbed, and it’s the perfect type of carb for boosting muscle glycogen, which can speed up muscle growth. If you don’t know what maltodextrin is, it’s a simple starch derived from corn. It’s very similar to white rice, except it comes as a powder, making it easier to mix into a shake, easier to consume in large quantities, and similarly easy to digest.

Now, in some circles, carbs are thought of as being bad. And for some people, that may even be true. But for skinny guys, athletic performance, weight training, and building muscle, carbs tend to be great. The Journal of the International Society of Sports Nutrition recommends getting most of our extra calories from carbs, which often works out to around 40–60% of our overall calories. The National Strength & Conditioning association makes similar recommendations, noting that getting 45–65% of our calories from carbohydrates tends to be best for our general health, best for weight training, and best for gaining muscle. This lines up with all of the modern hypertrophy research, too (studystudy). So this idea of supplementing with extra carbs is evidence-based (and it explains Gatorade and whatnot, too).

Anyway, when protein and carbs are combined together like this, it gives us a simple meal replacement that’s effortless to prepare and easy on our appetites, making it easier to eat more calories overall. That’s why mass gainers are so good for helping skinny guys gain weight: they’re an easy source of muscle-building calories.

Jared's before and after progress photos showing him going from being a skinny ectomorph to being muscular.

Here’s a photo of Jared gaining his first 27 pounds during his first few months of lifting—his so-called “newbie gains“—going from being underweight to having a healthy body weight. When doing this, he was doing three full-body workouts per week and having a mass gainer after every workout. Sometimes we’d make the mass gainers ourselves out of whey and maltodextrin, other times we’d buy them pre-made. Either approach is fine.

Before and after progress photos showing Shane Duquette bulking up with mass gainers.

I’ve used mass gainers myself, too. And although I’ve always dreaded having to drink them, they’ve reliably helped me eat enough calories to build muscle. In the above photo, this is me during my second bulk, going from 150 up to 175 pounds over the course of three months.

Were the mass gainers instrumental to our success? Not really, no. They just boosted our protein, carb, and calorie intake high enough to allow us to build muscle at full speed.

Before and after photo of a skinny guy building muscle

Since then, we’ve helped a little over 10,000 skinny guys bulk up, and we’ve always listed some form of mass gainer as an optional tool for people. Some guys choose to use them, many guys don’t. Some guys use them during their first bulks and then find that they don’t need them anymore, or vice versa. Regardless, they all get comparable results.

I don’t use mass gainers very much anymore. Nowadays when I’m trying to gain weight, I’ll have a whey shake, a cup of trail mix, and a small loaf of pan de muerto. My appetite isn’t as much of a limiting factor anymore, and so I prefer to get the extra calories from (somewhat) whole foods. Plus, the goal isn’t to use weight gainers forever, just to use them during the period of your life when you need them.

So, do weight gainers work? Absolutely. But do you need them? Not at all. They’re just a tool to help you consume enough protein and calories.

Are Mass Gainers Healthy?

Mass gainers don’t usually contain very many micronutrients, vitamins, minerals, or fibre. If you replaced all of your meals with mass gainers, your diet would become deficient in all of those things, and that could certainly harm your general health, especially if you persisted with it for a long time. But if you’re already consuming meat, dairy, eggs, fruits, veggies, nuts, olive oil, grains, and legumes in your regular diet, and then you add in a mass gainer shake, then it’s no problem.

Remember, bulking means add extra foods into our diets. We have a surplus of calories. We’re eating an abundance of food. That leaves plenty of room for simple calories. So although the mass gainer isn’t adding micronutrients into your diet, if you already have enough of them, that’s not really a problem.

Illustration of a skinny hardgainer eating a feast in his attempt to bulk up, gain weight. and build muscle.

Now, if your diet is already somewhat poor, if you’re already eating a lot of processed foods, if you aren’t eating lots of nuts, fruits, and veggies, then things change. In that case, you’re adding empty calories into a diet that’s already deficient. Instead of supplementing with a mass gainer, it might make more sense to blend up a smoothie instead. For example, every morning for breakfast, you could blend up some whey, spinach, oats, nuts, a banana, some yoghurt, and frozen berries. That way you’re adding a ton of nutritious calories into your diet along with the protein and starchy carbs.

Illustration of a doctor checking a skinny and muscular man to see if they're healthy.

The other thing to keep in mind is that going from being skinny to being strong and muscular is a huge boon to our general health. Building muscle, gaining strength, and habitually lifting weights are all incredibly healthy, and if a weight gainer is what facilitates your progress, then it can lead to an improvement in your health. With that said, although Marco has a degree in Health Sciences, we aren’t doctors or nutritionists, so take that with a grain of creatine.

So, mass gainers aren’t inherently healthy or unhealthy, it just depends on how they fit into your overall diet. If you eat a generally good diet but you’re having trouble gaining weight, mass gainers can be great. On the other hand, if you eat a poor diet, more processed calories probably aren’t what you need.

What’s the Best Way to Use Mass Gainers?

As a general rule of thumb, a skinny beginner might want to gain somewhere between 0.5–1 pound per week on the scale. If you’re struggling to gain weight consistently, try consuming a mass gainer after every workout. If that’s still not moving the scale up, try consuming a mass gainer on rest days, too. If that’s still not working, you might enjoy our article on how to eat more calories.

Illustration of a skinny ectomorph doing an underhand chin-up.

The benefit of having your mass gainers after working out is twofold:

  • That whole idea of an “anabolic post-workout window,” where we need to consume a bunch of protein and calories is often overblown (study), but even so, it’s a great time to consume a ton of carbs. When I asked one of the researchers who conducted the above study about whether we should be having maltodextrin/weight gainers after working out, he said, “Post-workout carbohydrates shouldn’t cause you any trouble in the long run as you are extremely insulin sensitive after training. As long as you maintain a good diet, good activity, keep your body fat low, and your fasting blood sugar remains normal, then you should be fine.”
  • After working out, a lot of skinny guys find it hard to eat a big meal. Maybe that’s because they need to change, shower, and then head home from the gym. Maybe it’s because their pre-workout supplement blunted their appetite. Or maybe lifting kills their appetite for a couple of hours. In any case, sipping on a mass gainer while training and then chugging what’s left at the end ensures that we’re not falling behind on our calories.

Now, the real trick with mass gainers is to make sure that it isn’t causing you to gain weight too quickly. If you’re gaining 0.5–1 pound per week, no problem. But if you’re gaining much more than that, especially for more than a week or two in a row, you might want to slow things down. It’s not that the weight gainer itself is fattening, it’s just that you’re consuming too many calories overall, gaining weight too fast. On that note…

Do Weight Gainers Cause Excess Fat Gain?

No, mass gainers shouldn’t cause you to gain extra fat, provided that you’re not consuming too many calories overall. The serving sizes are quite large, though, and mass gainers tend to be quite easy on the appetite, so it’s common for people to overdo it. That isn’t because the mass gainers are fattening, though, it’s just because they’re consuming too many calories and gaining weight too fast.

Illustration showing a skinny guy gaining fat from mass gainers.

Keep in mind that mass gainers are specifically engineered to make it easier to gain muscle without excess fat gain. They almost always contain enough protein to fully spike muscle protein synthesis, which is great for building muscle quickly and leanly. They also contain starchy carbs, which are great for increasing glycogen storage, great for building muscle, and very unlikely to be stored as body fat. And they’re low in fat, which is the macronutrient that’s most likely to be stored as body fat, especially when that fat is processed.

Are Mass Gainers Better than Real Food?

Nope! If you want to get your calories from real food instead, no problem—you aren’t missing out on anything. Mass gainers aren’t a magical muscle-building supplement, they’re just an easy source of calories that aren’t very filling. They’re a useful tool for people who struggle to gain weight when they eat real food.

Illustration of a bowl of oatmeal

There are plenty of great bulking foods that make great alternatives to mass gainers, and we have a list of them in this article.

Should You Have Mass Gainers Before Bed?

We go into this in more detail in our article on sleeping for muscle growth, but it’s usually a bad idea to consume a bunch of simple carbs and whey protein before bed. Our body temperature goes up, which can make you twitchy and sweaty. Plus, the whey protein quickly breaks down into amino acids, one of which is tryptophan, which can interfere with our production of melatonin, making it harder to fall and stay asleep.

Illustration of a man sleeping.

On the other hand, if you have your weight gainer while working out, the extra energy from the maltodextrin becomes a bonus, improving your muscular endurance while training. They whey protein will still break down into various amino acids, including tryptophan, but that becomes a good thing. Tryptophan acts as a precursor to melatonin, so as long as you have it far enough away from your bedtime, it can actually lean to more melatonin production, improving your sleep.

It’s usually better to have smaller meals and more slowly digested protein before bed, if you can help it. Meat is fine in the evening, as is casein protein, which is found in cottage cheese, greek yoghurt, and casein protein powder. So a better pre-bed “weight gainer” might be some oatmeal with casein mixed in. Or maybe some cottage cheese with a bit of strawberry jam. That kind of thing.

Mass Gainers and Stomach Aches

It’s common for people to get a stomach ache after having a mass gainer shake. That used to happen to me, and we’ve had a number of members in our community struggle with it, too. Knowing how unpleasant that can be, it’s always made me hesitant to recommend them. However, the problem stems mainly from the fact that the serving sizes are so obnoxiously large. The stomach ache we get from eating 1,250 calories of a weight gainer is often fairly similar to the upset we’d get from eating a 1,250-calorie meal.

There are a couple good ways of avoiding stomach aches:

  • Reduce the serving size. Instead of consuming the 1,250-calorie servings that are ubiquitous with weight gainers, try having 50–75% of the dosage, giving you more like 625–800 calories per serving.
  • Consume the weight gainers during or right after working out. My favourite way of doing this is sipping on my mass gainer while working out, then chugging whatever’s left at the end of my workout. I’ve never had stomach problems that way, and it often gives me great energy while training.
  • Make sure you’re having enough water with your mass gainers. You may need to mix one scoop into a glass, drink it, and then mix up a second scoop.
  • Use a blender bottle. They’re usually big enough to fit plenty of water, and they have a little blender spring to help break up the clumps. I like this one from Rogue.

What’s the Best Mass Gainer?

The nice thing about mass gainers is that they aren’t anything fancy or revolutionary, they’re just a ton of easily digestible calories. Still, the best mass gainers all share a few key characteristics:

  • They contain enough protein to fully spike muscle-protein synthesis. Depending on the protein source, that’s usually in the neighbourhood of around 50 grams of protein per serving.
  • They contain a ton of easily digested starchy carbs. The source can vary, but maltodextrin is popular, and that’s perfect. A typical weight gainer contains around 250 grams of carbs per serving.
  • They don’t contain much fat. A few grams is fine, but much more than that usually isn’t great. Better to get your fats from whole foods, such as nuts, eggs, olive oil, avocados, fish, and so on.

There are a ton of brands that make mass gainers that match these specifications, so the main trick is just to find a company that you trust. Maltodextrin is one of the cheapest supplement ingredients, so it’s unlikely it will be under-dosed. But whey is more of a premium powder, so it’s possible that a mass gainer shake might exaggerate the amount of protein, replacing some of it with extra maltodextrin. That’s why choosing a brand you trust is important.

There are a few brands that have built a good reputation for making high-quality supplements with accurate dosages. Optimum Nutrition is perhaps the most famous example, and their mass gainer, Serious Mass, is one that I’ve had good experiences with, both personally and with members in our community.

Summary

Bony to Beastly illustration showing a skinny guy bulking up with mass gainer supplements.

We tend to run into two stances on mass gainers:

  1. Mass gainers are supplements, and supplements are basically cheat codes. Therefore, mass gainers are better than whole foods for bulking up. You’re missing out if you don’t use them.
  2. Mass gainers are supplements, and supplements aren’t as good as whole foods. Nobody should use them.

As you can probably guess, the answer is somewhere in the middle. Some people really do benefit from mass gainers, especially skinny guys who are having trouble gaining weight. They won’t speed up the rate that your body can build muscle, though, they’ll just make it easier to eat more of the right kinds of calories—protein and starchy carbs. And given how important it is to eat enough protein, calories, and carbs, that can be a real game-changer.

On the other hand, whole foods are an important part of eating a good, healthy diet. Most of the time, most of your calories should come from real foods. But that doesn’t mean that supplements can’t be a good addition to your diet, or that they’re inherently unhealthy or ineffective. In fact, the whey protein and maltodextrin found in mass gainers are both pretty much perfect for building muscle.

If your diet is already pretty crummy, though—lacking in whole foods, low in fruits, veggies, and legumes—then maybe you’d be better off blending up a smoothie instead of buying a weight gainer. Blending up some oats, whey, yoghurt, bananas, frozen berries, spinach, and nuts is probably a better bet.

Shane Duquette is the co-founder and creative lead of Outlift, Bony to Beastly, and Bony to Bombshell, and has a degree in design from York University in Toronto, Canada. He's personally gained sixty pounds at 11% body fat and has nine years of experience helping nearly ten thousand skinny people bulk up.

Marco Walker-Ng is the co-founder and strength coach of Outlift, Bony to Beastly, and Bony to Bombshell, and is a certified trainer (PTS) with a Bachelor's degree in Health Sciences (BHSc) from the University of Ottawa. His specialty is helping people build muscle to improve their strength and general health, with clients including college, professional, and Olympic athletes.

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