Illustration showing a weight gainer supplement.

Should Skinny Women Use Weight Gainers?

“Weight gainers,” also known as “mass gainers,” are high-calorie supplements designed to help naturally skinny women gain weight. They’re almost always made of protein powder, carb powder, and some flavouring to make them more palatable.

The idea is that by drinking all of these calories, you can gain weight more easily. These weight gainer shakes aren’t as filling as real food. You don’t need to cook or prepare it. And you can chug the shake in a few seconds flat. There’s no denying that weight gainers can make things easier. No wonder they’re so popular.

So, do they work? Should you use them? Are there any downsides or side effects? And what kind of results can you expect if you start taking them?

Let’s take a dive.

Before and after photo showing the results of a woman taking weight gainers.

Why Skinny Women Take Weight Gainers

It’s common for skinny women to be interested in weight gainers, ask for advice, and be told, “Just eat more!” But if you’re naturally thin, you’ve probably heard that kind of thing before. “Just eat a burger.” Or whatever.

This advice sucks because eating enough calories to gain weight can be challenging. Yes, most people gain weight easily. Yes, most people can “just eat more.” But skinny women can have smaller stomachs, faster metabolisms, and more meagre appetites. Eating enough calories to gain weight can be hard.

Plus, eating more real food means cooking more real food. Sometimes that can take too much time or energy, especially if you can’t fit much in your stomach, so you’re trying to eat 3–4 meals plus a couple of snacks.

Illustration of a weight gainer supplement for women.

The selling point of weight gainers is that they aren’t as filling as real food, making it easier to eat more calories. And mixing some powder into water isn’t nearly as difficult as preparing a real meal—not to mention the dishes! These are real selling points.

For more, we have a full article on why it’s so hard for some women to gain weight.

Do Weight Gainers Work?

Weight gainers do work. To gain weight, you need to eat more calories than you burn. Weight gainers contain a ton of calories. If those calories drive you into a calorie surplus, you’ll gain weight.

Most women aren’t just trying to gain weight, though—they’re trying to build muscle. Weight gainers can help with that, too. Most weight gainers contain at least one serving of protein (27 grams) and often more (50+ grams). We build muscle out of the protein we eat, so eating enough protein can help us gain more muscle, less fat.

To maximize your rate of muscle growth, you need around 0.7–1 gram of protein per pound bodyweight per day. So if you weigh 100 pounds, you should aim to eat at least 70–100 grams of protein per day. Weight gainers can help with that, as can protein powders.

Weight gainers also contain a ton of carbs. It’s common for overweight people to avoid carbs. And it’s true that foods that are higher in carbs can be easier to overeat. Soda is an infamous example of that. The thing is, carbs can also be super helpful for building muscle. Our muscles store carbs in the form of glycogen, and that glycogen makes our muscles fuller and stronger (studystudy). That’s why The Journal of the International Society of Sports Nutrition recommends getting around half of our calories from carbs when trying to build muscle.

So by combining protein, carbs, and calories, weight gainers can help you gain muscle, strength, and weight, especially if you’re using them while following a good workout program.

For more, we have a full article on how to eat a good bulking diet.

What Results Can You Expect?

In a 2002 study by Rozenek et al., the participants were put on a weight training program to stimulate muscle growth. Some were given a weight gainer, some were given carbohydrate powder, and some weren’t given anything.

Results of a study looking at weight gainer supplements for muscle growth.

The participants supplementing with weight gainers were able to gain 7.5 pounds of lean mass while losing half a pound of fat, resulting in 7 pounds gained overall. The study was eight weeks long, so the weight gainer helped them gain about a pound per week.

Mind you, the participants in this study were men. As a woman, you’d probably want to cut that rate of weight gain in half. Gaining around 0.5 pounds per week tends to work better for skinny women trying to build muscle. If you do that, it’s reasonable to expect about half the results shown in the above study. So around 3–4 pounds of muscle in a little under two months.

Before and after photo of a woman's weight gain transformation

We see weight-gain results like that all the time. If you’re thinner, you can expect to gain muscle a little bit faster. If you’re naturally leaner, you might not need to worry as much about gaining fat. And if you’re new to lifting, you can expect a period of fast muscle growth when you first start weight training.

Are Weight Gainers Healthy?

The thing is, to get results like we’ve shown above, you don’t need to take weight gainers. Weight gainers are just a source of protein, carbs, and calories. You can get those nutrients from anywhere. And if you get more of your calories from unprocessed whole foods, you’ll be getting more vitamins, minerals, fibre, probiotics, and phytonutrients. You might make slightly better progress without the weight gainer.

There’s nothing inherently unhealthy about the ingredients in a weight gainer. Gainers are just a mix of:

  • Protein powder, usually whey protein concentrate or a plant-based alternative. Protein powders are a great source of protein for building muscle.
  • Carbohydrate powder, usually maltodextrin. This is the more controversial part. Should you be supplementing with hundreds of calories of processed carbs? It’s hard to say. If your diet is really good, then you’re getting your micronutrients elsewhere, and so it’s not necessarily a problem. You could count this like a dessert. (Some weight gainers also use ground oats, which is perhaps a healthier option. Just watch out not to overdo it. Too much fibre can be hard to digest.)
  • Flavourings, either articial or natural. Maybe some cocoa and sucralose and a few other ingredients that probably won’t have much impact on your health when used in moderation.

If you can manage it, though, blending up some weight-gain smoothies might be a healthier approach. You’ll get just as much protein and just as many calories, but you’ll also get more vitamins, minerals, fibre, probiotics, and phytonutrients. Blending up some bananas, oats, spinach, greek yogurt, and frozen berries with water works great. And then just add a scoop of whey if you need extra protein. That’s how we get results for the women doing our weight-gain program:

Before and after photo of a woman gaining weight.

How to Use a Weight Gainer

As a rule of thumb, we recommend getting around 80% of your calories from foods that aren’t super processed. Most foods are processed to some degree, and you don’t need to be super strict about it, but think of foods like fruits, veggies, legumes, meat, poultry, fish, dairy, nuts, seeds, yogurt, kefir, extra-virgin olive oil, eggs, and so on. Get most of your calories from foods like that.

The problem with weight gainers isn’t just that they’re processed, but also that they contain a TON of calories. A single serving of Serious Mass by Optimum Nutrition contains 1250–1500 calories. That’s probably around half your calories for the day, even when gaining weight. That’s too many processed calories.

The reason weight gainers have such enormous serving sizes is that they’re made for men. Men are larger and burn more calories. And when men try to gain weight, they can do with a calorie surplus that’s twice as big. But even for men, we don’t recommend taking full servings of weight gainers.

If you’re using a weight gainer, we recommend cutting the serving size in half. Aim for 500–600 calories per serving instead of 1250-1500. You could take the weight gainer if you don’t have access to a proper meal. You could also take it after working out. You don’t need to take it every day. Just use it when you need it.

The Verdict

Weight gainers do work, but they aren’t the only way to gain weight or build muscle. The main takeaway is that you can gain weight by:

  • Following a good weight lifting program. Ideally, one designed to stimulate muscle growth.
  • Eating enough protein to build muscle. Eating at least 0.7 grams of protein per pound bodyweight per day
  • Eating enough calories to gain weight. Eating around 250 extra calories per day will help you gain around half a pound per week. You’ll then need to adjust your intake based on how much weight you gain on the scale each week.
  • Trying your best to get a good night’s rest. Getting proper sleep will improve your willpower, energy, and muscle growth. And it can help limit fat gain while gaining weight.

If you’re doing those four things, you’ll do a great job of building muscle. Weight gainers can help you eat enough protein and calories, so they can indeed help you build muscle. But there are many other ways to eat enough protein and calories.

As a default, we recommend making weight-gain smoothies instead of using weight gainers. You can get creative with your smoothies, too. Here’s a homemade egg-nog recipe. That way, you’re building your weight-gain diet out of whole foods instead of processed supplements. Weight gainers can be handy in a pinch, and I’ve used them to gain weight in the past, but it’s hard to beat a smoothie for healthily building muscle.

What Next?

If you liked this article, I think you’d love our muscle-building newsletter. We’ll keep you up to date on all the latest muscle-building information for women. Or, if you want us to walk you through the process of building muscle, including teaching you the lifts, giving you an entire workout program, a complete diet guide, a recipe book, and online coaching, check out our Bony to Bombshell Program.

Shane Duquette is the co-founder of Outlift, Bony to Beastly, and Bony to Bombshell, and has a degree in design from York University in Toronto, Canada. He's gained sixty pounds at 11% body fat and has over ten years of experience helping over 10,000 skinny people build muscle, get stronger, and gain weight.

Cassandra González Duquette is a certified nutritionist (CNP) who studied at the Institute of Holistic Nutrition in Toronto, Canada. She's personally gained 22 pounds, going from 97 up to 119 pounds.