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The goal of a mass gainer is to help you gain weight – but does taking a mass gainer increase belly fat?
For many people, this can be a daunting prospect, and makes weight gain uncertain or even anxious.
It’s no surprise that some people are concerned about gaining fat with mass gainers.
Today we’ll look at how mass gainer supplements work, their role in fat gain, and how you can adjust your diet to make sure you get the best quality of weight gain while you commit to a real calorie surplus…
Mass Gainer Supplement: Goal And Mechanism
Mass gainers work by helping you increase your calorie intake, much like any other kind of food. They’re just a combination of pure, high-concentration protein and carbohydrates.
These are not fundamentally different from food sources – they’re just easier to consume and lack the vitamins and minerals of real food.
This means that mass gainer doesn’t have a higher risk of causing belly fat than any other food. What’s most important is the effect that it has on your daily calorie intake – as too much (with too little protein) can cause extra fat gain.
Mass gainers do contain a particularly high calorie content, which is the real risk for belly fat. If you’re trying to gain high-quality muscle mass and reduce fat, then you want to maintain a modest weight gain process: the slower you go, the more likely it is to be lean.
Super-high-calorie mass gainers are more of a risk, as they put you into a particularly harsh calorie surplus.
The ratio of calories to protein in a mass gainer is also important. Higher protein intake means less fat mass, more muscle mass, and better overall metabolic health.
It also evens out the release of both protein and carbs into the bloodstream for better insulin levels – as well as better muscle growth (1).
Proteins that are rich in Leucine and Isoleucine are particularly useful, as they prevent muscle breakdown and support direct muscle growth signaling.
This makes them a huge benefit, if you can get a BCAA-rich mass gainer for weight gain.
Recommended: Checkout the list of best mass gainers we’ve reviewed for skinny guys by clicking here.
Does Taking A Mass Gainer Increase Belly Fat?
No – taking a mass gainer will not simply cause an increase in belly fat. It’s possible to use a mass gainer and even lose weight. Mass gainers are just a high-calorie food supplement that you can use to increase the calorie content of your diet.
If you’re eating more than you’re burning through exercise and activity, you may gain belly fat. However, a small calorie deficit when paired with exercise will build muscle rather than fat (2).
Equally, a very-high protein diet can reduce belly fat gain, so you may want to use a high-protein mass gainer to prevent fat gain.
Calorie Balance: Mass Gainers, Energy Intake, and Overeating
Mass gainer will only cause belly fat gain if your diet is too calorie-dense for your activity levels and needs.
Even then, it is also likely to contribute to muscle gains before fat gains and – finally – you may not gain belly fat when you do gain fat.
There are lots of ways you can use a mass gainer that make use of the calorie content without actually causing belly fat gain.
Most people don’t experience significant belly fat gain early on – as this typically takes sustained overeating and mass gainers are popular among skinny guys.
Recommended: Here are some other mass gainer related articles we’ve covered:
How to Use a Mass Gainer?
How Long Does It Take For Mass Gainers to Work?
The Best Tasting Mass Gainers List
Don’t Fixate On Fat Gain
If you’re struggling to eat enough, then the risk of gaining a little extra fat is quite small. It’s also easier to burn belly fat than it is to gain high-quality weight, so it’s easier to take this risk.
Most skinny guys, for example, are simply not eating enough. The commitment to eating a calorie surplus is one of the most important ways to improve muscle gains as well as strength and long-term performance.
Mass gainers make the high-quality weight gain process easier – and the risk of fat gain is both low (if used properly), and offset by the possible weight-gain benefits.
Frequently Asked Questions
Do Mass Gainers Cause Fat Gain?
Mass gainers will not directly cause fat gain. Fat is gained when you eat a calorie surplus that is greater than your body’s needs for building muscle mass. This means you will typically need to eat over 500 calories of surplus if you’re performing resistance training or other forms of exercise.
A low protein diet also increases the risk of fat mass gain when gaining weight. Mass gainers are typically high protein to support muscle growth and reduce fat mass gain.
You should watch out for super-high-calorie mass gainers – and particularly those without much protein. A better protein-per-calorie content is a great way to improve the quality of your weight gain.
How Do You Minimize Fat Gain When Building Muscle?
You can minimize fat gains when building muscle by using a small calorie surplus – around 500 over your Total Daily Energy Expenditure (TDEE).
This slows down the weight gain process but also improves your muscle gain while preventing fat gains.
You can also reduce fat gains by increasing your total protein intake. Super high protein diets have been shown to reduce fat gain all the way down to zero in some cases, using super high intake.
You don’t need to go as far as these studies – a high protein intake is key to tipping the scales towards muscle gain and away from fat mass over time.
What’s The Best Mass Gainer For Lean Muscle Gains?
In our opinion, Optimum Nutrition Pro Gainer is one of the best mass gainer for lean muscle mass gains and reducing fat mass.
It’s a mass gainer with a very high protein per calorie ratio and uses a modest 650 calories per serving. This is half of some other super-heavy-duty options on the market and offers a mild and lean alternative to many mass gainers out there.
This makes ON Pro Gainer one of the most efficient and muscle-building mass gainers on the market while still offering good taste and a small, but powerful, boost to your calorie surplus.
It offers the best of both worlds for a lean bulk or patient weight-gain diet with the best quality healthy weight gain.
Conclusion: Our Final Thoughts
Weight gain with a mass gainer doesn’t need to involve getting fat. It’s a process that responds to the balance you strike between eating more and eating well. Some mass gainers – like ON Pro Gainer – are perfectly set up to support lean muscle mass gains without any extra fat gains.
Focusing on a sustainable and patient weight gain diet can help you prevent belly fat.
It’s a risk that only goes up when the quality of your diet and its protein content drop, or when you start really overeating – even for a calorie surplus!
The quality and quantity of weight gain diets tend to compete. Slower is usually better, while faster typically means more fat gain and belly fat in particular.
Key Takeaway
Getting the most out of your weight gain diet comes from striking a patient but committed balance for calorie surplus.
You Might Like:
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- Are Mass Gainers Bad For You?
- What Type Of Whey Protein is Best For Weight Gain?
- Is Mass Gainer Good For Bulking?

Rohan Arora is a Certified Personal Trainer and Sports Nutritionist and has been actively involved in sports and fitness for over 8 years. He now leads the team of fitness specialists and personal trainers who help people around the world with personalized workout and nutrition plans, along with providing the right information on sports supplements.