Does Mass Gainer Make You Fat? (weight gain, belly fat)

January 9, 2024 |

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Mass gainers are a nutrition supplement that helps skinny people bulk up and build muscle.

They’re particularly popular among skinny young men who want to become more muscular and improve their physique and confidence.

Mass gainers are high-calorie supplements that typically focus on carbohydrates and protein content.

These are the two most important macronutrients for muscle growth, so it only makes sense that they’re the most abundant ingredients in a mass gainer.

They also come as a powder you mix into a liquid (often milk or water) to produce a shake.

This is important because it reduces the fullness you experience afterward, huge help for anyone with a low appetite that gets full easily when eating real food.

It’s a real limitation to weight gain and muscle growth for some people.

Mass gainers can be a useful addition to solving this problem.

Many mass gainer supplements are as simple as combining a carbohydrate powder with a whey protein powder (or plant counterpart).

This means that mass gainers offer a fast-absorbing source of carbs and protein, making them high-calorie but also very well suited to post-workout recovery shake use.

How Does Mass Gainer Work?

Mass gainer supplements build muscle by providing your body with the energy needed to repair and grow muscles after intense exercise.

The idea is that you add a mass gainer shake to a normal, healthy, well-balanced diet.

The extra calories should take you from equal intake and output of energy to a calorie surplus.

A calorie surplus is when you get more calories through food than you burn for exercise and activity. This produces abundant energy levels to grow more muscle and strengthen other tissues.

The protein in mass gainer supplements (and your diet in general) are used as the resources for building these tissues.

Because muscle mass is mostly protein, it is a perfect target for growth.

CrazyNutrition Mass Gainer bottle

Mass gainers have good theoretical benefits – but many new users fear gaining fat.

Mass gainers’ high-calorie content can be a risk for unwanted fat gains if you’re not careful, and this has made it a common limitation for some skinny guys looking to build more muscle.

Does Mass Gainer Make You Fat?

No, Mass Gainer doesn’t make you fat by itself, but it can cause unwanted fat gains if you over-eat. The goal of a mass gainer is to build muscle, which means that it needs to be used in appropriate amounts and with proper exercise, diet, and sleep habits.

You can use mass gainer to gain weight – but that weight would ideally be muscle mass. Excess fat gains happen when you try to gain weight too quickly or don’t eat enough protein.

Gaining weight too quickly is possible and sometimes easy with mass gainers.

Super mass gainers like Optimum Nutrition Serious Mass and others are super high calories – which may be too much for the average person.

ON serious mass

With servings of around 1200-1300 calories, this kind of product can easily lead to over-eating.

For reference, the average person will build muscle mass at around 500 calories over daily maintenance needs.

If you use one of these super mass gainers on top of a normal diet, you may be gaining around 500-800 calories’ worth of fat per day.

This is why asking if you need a mass gainer is important.

It’s important to track your calorie intake when building muscle.

It’s also an important step in choosing a mass gainer and understanding how much it will affect your diet – for both muscle and fat gains.

Mass Gainer & Fat – FAQs

Does Mass Gainer Make You Gain Weight?

Yes – mass gainer supplements are designed to help you gain weight – specifically muscle mass.

If you add a mass gainer to a normal, maintenance-level diet, you will start to gain weight and – if exercising – muscle mass.

The goal of a mass gainer is to make a calorie surplus easier, supporting the energy and protein needs of the body for muscle growth.

This requires effective exercise, diet, and sleep; Mass Gainer won’t do all the work for you.

You will not gain weight with a Mass Gainer if you don’t eat enough, and you may gain fat if you’re not exercising enough or eating enough protein in the rest of your diet.

Make sure not to rely on Mass Gainer for most dietary calories, carbs, or protein. Real food is still the most important change you should make.

Why Do Skinny Guys Use Mass Gainer?

Skinny guys use mass gainer supplements because they make weight gain much easier.

As a liquid calorie source, you can consume more calories with mass gainer than you might through food alone, requiring less appetite.

Many skinny guys are already small eaters, which can lead to low appetite, a hard time eating larger meals, or staying fuller for longer after food.

This means that eating more can be difficult.

Mass gainers are easier to use, can be carried around for convenience before mixing, and are typically a good post-workout option.

These all make mass gainers more convenient for skinny guys and offer a simple but effective option for the nutrients they need for muscle growth and weight gain.

Are Mass Gainers Worth It?

That depends on how much you struggle to gain weight and which product you buy.

Mass gainers are typically less expensive than supplements like whey protein per kilogram or pound simply because you will be buying more in a container and using more per scoop.

Mass gainers are not worth it if you can eat the required calories in food and you have the time and prep opportunities you need to do that.

However, this requires more cooking time and isn’t available to everyone.

Mass gainers are worth it if you’re struggling to get enough calories, can’t make meals, are busy during the day, and have no kitchen access (e.g., at work or university).

It is worth it if you’re looking for a cheap way to add more calories and protein to your diet.

One of the best value options is buying a leaner mass gainer with smaller scoops and more protein-per-serving but lower calories.

Alternatively, you can use a super mass gainer and only 30-50% of the recommended serving for an easy, inexpensive post-workout recovery shake.

Do Weight Gainers Work?

Yes – weight gainer supplements are typically effective at improving your calorie intake.

They are effective at supporting muscle growth and weight gain.

Mass gainer shakes are a sub-set of weight gainers, and they work very reliably since they’re just a calorie-dense food supplement.

The important thing is to avoid high-sugar mass gainers, which will help you gain weight but may cause metabolic damage along the way.

It’s better to be patient with this kind of supplement.

Ensure that your carb powder comes from a good source – ideally, a mixture of different types of starchy carbs.

Does Mass Gainer Increase Belly Fat?

Mass Gainer won’t specifically increase belly fat even if you’re overeating and gaining unwanted fat.

There’s no indication that Mass Gainer will target belly fat, as your body typically increases fat storage across the whole body simultaneously.

At the very least, your body fat distribution is personal and down to your genetic and hormonal factors. Mass Gainer doesn’t change how you store fat or where.

If you’re prone to storing fat on your belly, then excess Mass Gainer may cause an increase in belly fat.

Remember, however, that Mass Gainer will only cause fat gain if you’re not exercising enough, over-eating, or your diet lacks adequate protein content.

Sort these out first before worrying about the mass gainer itself.

Should I Take Mass Gainer Every Day?

You should take Mass Gainer every day if you’re struggling to eat enough and need to supplement your calorie intake.

However, you shouldn’t take mass gainer daily if you’re using it as a post-workout recovery shake. In that case, you would only use it after workouts.

Daily mass gainer intake is a good rule of thumb for most people.

You’re still recovering for 36-48 hours after a workout, and increased nutrient intake is a great way to maintain energy levels and support muscle recovery and growth.

Just because you didn’t exercise that day doesn’t mean you’re not building muscle.

What are the Disadvantages of Mass Gainers?

There are no real disadvantages to mass gainer when used properly.

It can offer a moderate calorie surplus with fast-absorbing carbs and protein – exactly what your body needs to support muscle growth and high-quality, healthy weight gain.

There are disadvantages to misuse of mass gainer – or very low-quality supplements.

Mass gainers with high sugar content should be avoided for their negative health effects.

You should also ensure you’re getting a reasonable calorie surplus (around 500 per day) rather than a very high-calorie surplus (1000+).

This makes the difference between fat gains and muscle gains for most people.

You also can’t rely on mass gainer alone.

The rest of your diet should constantly improve, with a balanced diet focusing on high-quality proteins, starchy carbs, plenty of vegetables, and unsaturated fats.

You also need to drink plenty of water and get high-quality sleep to support the best quality muscle growth.


Mass gainer supplements have a bad reputation because they’re one of the first supplements that young guys get into, and they’re often used recklessly.

Mass Gainer can make you fat in those situations, but it requires overeating, under-exercising, and poor lifestyle balance.

Mass gainers will not make you fat alone – they’re just a food supplement.

It’s the same as any food: it won’t make you fat, but it can do if you use it as the route to over-eating, bad diet, or neglect other areas of lifestyle.

Mass gainer supplements are convenient for supporting healthy muscle growth and a weight gain diet.

Make sure that your choice of product, your choice of dose, and then the exercise and recovery habits around your mass gainer use are smart, appropriate, and healthy!

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