The Truth About Mass Gainers (According to Science)

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Mass gainers are one of the most misunderstood and debated nutritional supplements on the market today. 

For many hardgainers and serious trainees, they promise a fast, convenient, and effective way to increase calorie intake, boost muscle growth, and enhance recovery between training sessions. For others, they seem like calorie bombs packed with artificial ingredients, sugars, and low-quality ingredients.

My mission, and all of ours here at FeastGood, is to give you the facts you need to know about mass gainers so you can decide if they’re right for you.

Key Takeaways

In this article we’ll cover everything you need to know about mass gainers, including:

• Mass gainers can be an effective tool for hardgainers who struggle to eat enough calories and protein to support muscle growth.

• Transparent Labs Mass Gainer is my top pick thanks to third-party testing, transparent labels, and easy-to-digest formula.

• If a lifter is consuming enough calories and protein from whole foods in their diet, mass gainer supplements may not be necessary.

• If you are a lifter who is struggling to eat enough calories throughout the day or has issues with nutrient timing and quantity around workouts, then mass gainers could be a very effective tool to use in your training.

What Are Mass Gainers, Really?

Mass gainers are supplements that are rich in calories, carbohydrates, and protein. A serving of a mass gainer can be anywhere between 700-1200 calories, making it a convenient way to increase caloric intake.

They can be a game-changer for lifters who struggle to eat enough to stay in a calorie surplus, which is key for building muscle and gaining weight. For hardgainers especially, adding just one or two shakes a day can boost daily calorie intake by 10–30% without much effort.

Mass gainers are loaded with carbs, which are essential for muscle growth, recovery, and fueling tough workouts. They also include protein to support muscle repair and growth, and many come with added performance boosters like vitamins, minerals, and creatine.

In some fitness circles, mass gainers spark a lot of debate. While they can be a valuable tool for hardgainers, many products are loaded with low-quality ingredients that can lead to bloating and unwanted fat gain, especially if you don’t take the time to choose a clean, well-formulated option.

Let’s dive into what exactly goes into most mass gainers and shed some light on what ingredients and red flags you should be aware of.

What Ingredients Are In Mass Gainers?

Understanding what’s inside your mass gainer can make the difference between clean gains and bloating or fat gain. Here’s a breakdown of the most common ingredients and what they actually do for you:

Protein

Protein powder can come from a variety of sources like whey, casein, pea, hemp, and other vegan blends. Mass gainers always include protein to support muscle repair and growth.

Carbohydrates 

Carbohydrate powders boost your calorie intake and help refuel your muscles after intense training. Since your body relies on glucose during tough workouts, getting enough carbs can improve performance, speed up recovery, and support muscle growth.

Maltodextrin is the most common, it’s cheap, fast-digesting, and calorie-dense. It can cause bloating and blood sugar spikes, which is why some people prefer other sources.

I use maltodextrin because I want fast-digesting carbs that hit my bloodstream quickly during and after workouts. Slower-digesting carbs tend to fill me up too much, which defeats the purpose when I’m trying to eat more. In moderation, maltodextrin is safe for most healthy people.

Other sources of carbs are dextrose, oat powder, rice powder, sweet potato powder, and waxy maize. Each can vary based on taste (some less sweet than others), digestibility, and blood sugar control.

Fat

Fat is added to most mass gainers in the form of oils (seed, hydrogenated, or MCT depending on the brand). Fats provide additional calories, slow digestion, and can provide sustained energy.

Vitamins and Minerals

Mass gainers often include vitamins and minerals like B-complex, calcium, iron, magnesium, zinc, and vitamin D to support muscle function and metabolism. These help prevent nutrient gaps, especially if your bulking diet isn’t the cleanest.

Digestive Enzymes, Fiber, and Prebiotics

Some mass gainers include digestive enzymes, fiber, and prebiotics to improve digestion and gut health. Eating more calories can stress your digestive system, so these ingredients help reduce bloating, gas, and discomfort, especially if you’re sensitive to certain ingredients.

Artificial Sweeteners

Sweeteners, either plant-based (monk fruit extract, date sugar, stevia, agave) or not (aspartame, sucralose, dextrose, saccharin) are used to improve the palatability of the products. 

Some artificial sweeteners can cause digestive issues, so it’s important to check the ingredient list and see if you’re sensitive to any of them.

Thickening Agents and Emulsifiers

Thickening agents and emulsifiers like gums, lecithins, and starch are used to improve mixability and give texture to mass gainers. 

Some gums and lecithins can cause stomach upset (typically sunflower lecithin, pectin, acacia gum are avoided).

Creatine

Creatine is sometimes added to mass gainers because it is an effective supplement to promote muscle growth and increase strength. 

Are All Mass Gainers Created Equal?

No, mass gainers vary in their calorie and macronutrient (protein, carbs, and fat) per serving as well as the quality of their ingredients. 

Some offer more calories, but it often comes at a cost: cheap fillers, artificial ingredients, and digestive side effects like bloating or gas.

Red Flags

Watch out for:

• Added sugars, fillers and inexpensive low-quality carbs: these are a cheap way to get calories, however they can result in consuming too many processed carbs and calories, which could lead to GI distress or excess fat gain if you’re not keeping an eye on your total intake.

• Proprietary blends: This sounds cool, but they usually hide the exact ingredients and amounts, often covering up added sugars, fillers, or unnecessary extras that don’t actually support muscle growth; yet they charge extra for them.

What to Look For in a Mass Gainer

When selecting a mass gainer, you should look for one that delivers:

• High-quality protein like whey isolate, concentrate, or vegan options. 
• Complex carbs like oats or sweet potato are often better for slower digestion.
• Third-party testing to ensure purity and label accuracy.

Mass Gainer Product Recommendation

The mass gainer that I trust is from Transparent Labs. I recommend this product because it’s designed to deliver high-quality carbs, protein, and creatine, balanced to support muscle growth without unnecessary fillers.

The label transparency and accuracy is another reason why I chose this product, as I know exactly what is in the product and what is NOT. 

Unlike other brands that may be packed full of artificial sweeteners, low quality carbs, and unnecessary oils, Transparent Labs created a product that supplies high quality, clean macronutrients and performance enhancing creatine in the right amounts (just enough calorie surplus to gain muscle, not enough to gain excess body fat). 

You can read my full review of Transparent Labs Mass Gainer here.

Common Brands vs DIY Blends

There are a wide variety of mass gainers on the market today. Some lifters will purchase pre-made blends from common brands, while others will go the DIY route to have more control on what is going into their blends.

Common Brands (Budget Friendly and Premium Options)

Premium brands are known for adding minimal additional ingredients outside of protein, carbs, and fats. The sources of these macronutrients are not from artificial sweeteners or fillers, making these some of the cleanest and easily digestible blends on the market. They do, however, come at a price.

Top pick: Transparent Labs Mass Gainer. It delivers everything you need in a mass gainer and is third-party tested for quality.

Most budget options provide similar macros, however they tend to use lower-quality ingredients. If you notice you have issues with digesting these or want to prioritize ingredients to be sure you’re not consuming artificial sweeteners, gums, and fillers, then you may want to either seek out premium brands or go the DIY route.

DIY Blends

Creating your DIY blend can be worth the extra work if you want to have full control of what is going in your mass gainer (and maybe save some money as well). When you look at all the mass gainers out there, they all include protein, carbs, and sometimes fats.

You could buy protein powder, add a few scoops of carbohydrate powder, and top it off with creatine, prebiotics or fiber, and a multivitamin. But this approach takes planning and prep, which can make it harder to stay consistent. And consistency is key when you’re trying to gain weight.

How Many Calories Is a Serving of Mass Gainer?

Most mass gainers will deliver upwards of 1,000 calories per serving, or more! While this may be shocking, eating more calories on a daily basis is necessary for gaining mass. 

The total number of calories needed above your baseline can vary person to person, so be sure to track your calories to ensure you are not undereating (one serving may not be enough for some) or overeating (maybe you only need 500 calories not 1,000)!

It is also important to read the nutrition label and calorie content as each brand may use different size servings (scooper size if different or number of scoops for a serving).

The Science Behind Gaining Mass

To build muscle, you need to train hard in the gym with weights, be in a calorie surplus, and consume enough protein.

A calorie surplus means you are consuming more calories than your body needs to maintain its activity levels and energy output (workouts, daily life, etc). Generally speaking you want to be in a calorie surplus of 10-20% over your normal intake, which means for most people 300-800 calories per day.

In addition to eating enough calories, it’s important to have those calories come from protein, which helps repair and build new muscle tissue.

Your body also needs carbohydrates, a key part of mass gainers, because they’re your main fuel during intense training. Carbs are stored in your muscles as glycogen, and refilling those stores through your diet helps support consistent workouts, recovery, and muscle growth.

While adding only protein to your diet can help with recovery, it may not be enough for hard gainers and serious trainees looking to maximize muscle growth, as you may not be consuming enough calories and carbohydrates.

What the Research Says About Mass Gainers

To understand the effectiveness of mass gainers first we need to define the limitations in one’s diet that may be stopping them from increasing lean body mass. 

Research shows that to maximize muscle growth, you need both enough protein and a calorie surplus (eating more than you burn). If you’re eating enough protein but not enough total calories, your progress will still be limited.

Here’s what the research says about mass gainers compared to protein-only supplements and whole foods:

Study 1

Mass gainers are more effective than protein-only shakes if they help you achieve a calorie surplus, which is essential for gaining mass.

• View Study

Study 2

The extra carbs in mass gainers can boost workout performance and recovery by refilling glycogen stores. Allowing for more frequent and intense training, which supports muscle growth over time.

• View Study

Study 3 and 4

If adequate protein intake and total calories are appropriate (placing you in a surplus) through whole foods, there is no significant difference between achieving that through mass gainers or whole foods. 

That said, mass gainers may be more convenient to take in more calories at one time, and also come with the added benefit of creatine and other compounds that can boost workout recovery and performance.

• View Study
• View Study 

These studies were conducted on a diverse population sample, ranging from:

• Trained lifters
• Sport athletes (football)
• Endurance athletes

Who Should (and Shouldn’t) Use a Mass Gainer?

Mass gainers can be a very helpful supplemental tool to improve weight gain, muscle growth, and recovery (or use as a meal replacement). But they are not for everyone.

Who Should Use a Mass Gainer?

• Hardgainers who struggle consuming enough calories throughout the day to stay in a calorie surplus to drive weight and muscle gain.

• Lifters who can’t hit their protein and carb needs, especially around workouts, where nutrient timing can enhance performance and growth.

• Anyone looking for a convenient nutrient dense supplement to use as a well rounded meal replacement if they struggle eating throughout the day (if this is the case, choose one that has sweet potato, rice, or oat powders with MCTs to slow digestion).

Who Shouldn’t Use a Mass Gainer?

• Someone who is not trying to actively gain weight.

• People already gaining at a good pace (.25-.75% body mass per week).

• Lifters not training consistently or intensely, extra calories won’t turn into muscle without serious effort in the gym

Whole Food vs. Mass Gainer Supplements

When it comes to gaining muscle and mass, the key is to consume enough protein and total calories. Mass gainers can be helpful if you struggle to do so, however not necessary if you can get it from whole foods. 

That said, let’s break down the pros and cons of each.

Pros of Whole Foods

• Provide a wide range of vitamins, minerals, fiber, and antioxidants for overall health and recovery.

• Support better gut health and digestion, especially when based on whole grains, fruits, veggies, and lean proteins.

• Studies suggest whole foods may support muscle growth better because they contain extra nutrients not found in supplements.

Pros of Mass Gainer Supplements

• Highly convenient, great for busy people or those who struggle to eat enough throughout the day.

• Faster digestion, so you don’t feel too full between meals.

• Calorie dense meals that are helpful for hardgainers who struggle to eat large amounts of calories and nutrients at one sitting.

• Some mass gainers will add creatine and other nutrients helpful for recovery and further muscle growth.

Cons of Whole Foods

• Slower digestion due to fiber, which can leave you feeling too full to keep eating.

• Not as convenient to consume on the go or pack in a gym bag, and require pre-planning to get the right amounts of protein, carbs, and calories needed.

• May not be ideal to consume during or after workouts as your digestive tract may not be ready to handle large amounts of solid foods.

Cons of Mass Gainer Supplements

• Risk of excessive fat gain if you are not monitoring your overall intake, as it is very easy to consume too many calories to place yourself in too large of a calorie surplus.

• Low quality ingredients could cause blood sugar spikes and GI distress.

• Can often lack fiber and micronutrients, which may result in deficiencies if you are not pairing with whole foods.

• Can get expensive over time.

What Does 1,000 Calories From Whole Food vs Mass Gainers Look Like?

Here’s a breakdown of what 1,000 calories looks like from whole foods vs a mass gainer.

Mass Gainer

• 1 Scoop of Transparent Labs Mass Gainer
• 12oz Milk
• 1,000 calories, 53g protein, 126g carbs, 14g fat

Whole Foods

• 6oz chicken breast
• 1.5c cooked rice
• 1T olive oil
• 1,000 calories, 52g protein, 119g carbs, 14g fat
  

Final Verdict, Are Mass Gainers Worth It?

Mass gainers are 100% worth it IF their use is justified. If you are training hard, already eating foods, and still struggling to eat enough calories to stayf in a calorie surplus, then 100% you should try mass gainers. 

On the flip side, if you’re not trying to gain weight, already eating enough, or not training hard and often, then a mass gainer probably isn’t the right fit right now.

Bottom Line: Mass gainers work best when they fill a real gap in your diet, not when they’re used as a shortcut. For lifters who are already training hard and eating consistently but still falling short on calories, they can make a huge difference. But used carelessly, they’re just extra calories with a price tag, and that can lead to more fat than muscle.

References

Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J. Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training. Front Nutr. 2019 Aug 20;6:131. doi: 10.3389/fnut.2019.00131. PMID: 31482093; PMCID: PMC6710320.

Hatamoto, Y., Tanoue, Y., Tagawa, R., Yasukata, J., Shiose, K., Kose, Y., Watanabe, D., Tanaka, S., Chen, K. Y., Ebine, N., Ueda, K., Uehara, Y., Higaki, Y., Sanbongi, C., & Kawanaka, K. (2024). Greater energy surplus promotes body protein accretion in healthy young men: A randomized clinical trial. Clinical Nutrition, 43(12), 48–60. https://doi.org/10.1016/j.clnu.2024.09.035

Berardi JM, Price TB, Noreen EE, Lemon PW. Postexercise muscle glycogen recovery enhanced with a carbohydrate-protein supplement. Med Sci Sports Exerc. 2006 Jun;38(6):1106-13. doi: 10.1249/01.mss.0000222826.49358.f3. PMID: 16775553.

Jäger, R., Kerksick, C.M., Campbell, B.I. et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr 14, 20 (2017). https://doi.org/10.1186/s12970-017-0177-8

Naderi, A., Rothschild, J.A., Santos, H.O. et al. Nutritional Strategies to Improve Post-exercise Recovery and Subsequent Exercise Performance: A Narrative Review. Sports Med (2025). https://doi.org/10.1007/s40279-025-02213-6