Can mass gainers cause stomach problems? A deep dive into digestive issues

October 13, 2025 •

4 min read

According to anecdotal evidence from numerous users, digestive discomfort is one of the most commonly reported side effects when first introducing a mass gainer into their diet. Addressing the question, 'can mass gainers cause stomach problems?', this article explores why these supplements can upset your stomach and offers solutions for a smoother experience.

Quick Summary

Mass gainers can lead to stomach issues like bloating, gas, and cramps due to high calorie loads, ingredient sensitivities, or rapid consumption. The supplement's composition, particularly the protein source and type of carbohydrates, heavily influences digestive tolerance. Learning how to properly select and consume these products is key to avoiding discomfort.

Key Points

Lactose intolerance is a common trigger: Many mass gainers use whey concentrate, which contains lactose and can cause bloating and gas in sensitive individuals.
High calorie and sugar load can overwhelm the system: Large servings and simple carbs like maltodextrin can be difficult for the digestive system to handle all at once.
Consumption speed and hydration matter: Drinking your shake too quickly or not staying properly hydrated can exacerbate digestive problems.
Choose gainers with complex carbs and digestive enzymes: Opting for products with oats or other complex carbs and added enzymes can greatly improve digestibility.
Start with a half-serving and increase gradually: This allows your body time to adapt to the new high-calorie supplement and minimizes initial discomfort.

Understanding Why Mass Gainers Can Upset Your Stomach

It is a common scenario for fitness enthusiasts: you’ve added a mass gainer to your routine to accelerate muscle growth, but instead of just gains, you're experiencing bloating, gas, or cramps. The reason behind this digestive distress is not always a flaw in the product itself but a combination of its potent formula and your body’s individual response.

The Common Culprits Behind Digestive Issues

Several factors within a mass gainer's formula can contribute to stomach problems:

High Calorie and Macronutrient Load: A single serving of a mass gainer can contain hundreds or even over a thousand calories, often packed with large amounts of protein and carbohydrates. A sudden surge of this much dense nutrition can overwhelm the digestive system, which is not accustomed to processing such a large load at once. This can lead to feelings of heaviness and indigestion.
Lactose Intolerance: Many mass gainers use whey concentrate as a primary protein source, which contains lactose. For the estimated 65% of the global population with some form of lactose intolerance, this can trigger significant digestive upset, including gas, bloating, and diarrhea.
Low-Quality Carbohydrates: Cheaper mass gainers frequently use high glycemic index carbohydrates like maltodextrin and simple sugars to bulk up the calorie count. These can cause rapid spikes in blood sugar and may be harder for some people to digest, contributing to gas and discomfort.
Artificial Additives: The use of artificial sweeteners and flavors can also be a factor. Some individuals are sensitive to these compounds, experiencing digestive side effects like gas and bloating.
Lack of Digestive Enzymes: Some formulas lack the digestive enzymes necessary to help the body break down the large quantities of protein and carbs effectively. This poor absorption can lead to fermentation in the gut, causing gas and other symptoms.

How to Minimize or Prevent Stomach Discomfort

Fortunately, there are several strategies you can employ to mitigate or eliminate the digestive side effects associated with mass gainers. By adjusting your consumption habits and choosing the right product, you can still reap the benefits without the stomach ache.

Practical Tips for Better Digestion

Start Small and Split Servings: Instead of taking a full, large serving from day one, begin with a half-serving to allow your body to adapt. You can also split your total daily intake into two or more smaller shakes throughout the day, which is much easier on the digestive system than one massive shake.
Drink Slowly: Gulping down a high-calorie shake quickly can shock your digestive system. Sip your shake slowly over 10-15 minutes to aid digestion.
Stay Hydrated: Consuming plenty of water is crucial. Water helps with digestion, aids nutrient transport, and can alleviate cramps caused by the high protein content.
Mix with Water or Diluted Milk: If you suspect lactose intolerance, mixing your gainer with water is a great starting point. If you prefer a creamier texture, try using a plant-based milk or diluting regular milk with water.
Choose a High-Quality Gainer: Look for products that list digestive enzymes, use complex carbohydrate sources like oats, and have minimal artificial sweeteners. Checking for third-party testing can also ensure product quality and accurate labeling.

Comparing Different Types of Mass Gainers


Feature	Problematic Mass Gainer	Digestive-Friendly Mass Gainer
Protein Source	Often Whey Concentrate	Whey Isolate, Hydrolyzed Whey, or Plant-Based Protein
Carbohydrate Source	Maltodextrin, Simple Sugars	Oats, Sweet Potato Powder, Complex Carbs
Calorie Density	Very high, overwhelming per serving	Balanced, often designed for split servings
Additives	High in artificial sweeteners, colors	Fewer, natural sweeteners (e.g., stevia)
Enzymes	None or minimal	Includes digestive enzymes (e.g., lactase)

The Role of Whole Foods and Diet

It is important to remember that mass gainers are a supplement, not a meal replacement. A healthy, balanced diet rich in whole foods is the foundation for muscle growth and overall health. Relying solely on supplements can lead to nutrient imbalances and is not sustainable. Whole foods provide a wider spectrum of nutrients, fiber, and phytonutrients that support a healthy gut and metabolic process.

Conclusion

In conclusion, can mass gainers cause stomach problems? Yes, they can, but the issues are often manageable with the right approach. Digestive discomfort is a common, and often temporary, side effect that can be traced back to ingredients, consumption habits, or individual sensitivities. By starting with smaller servings, hydrating properly, and carefully selecting a high-quality product, you can significantly reduce the risk of bloating, gas, and cramps. Remember to listen to your body and consult a healthcare professional if symptoms persist. Incorporating a well-chosen mass gainer alongside a diet of whole foods can help you achieve your fitness goals without compromising your digestive comfort.

For more information on digestive-friendly supplements and nutrition, consider visiting Naked Nutrition's blog for product and dietary advice.

Frequently Asked Questions

Mass gainers can cause bloating due to high calorie load, lactose content (if dairy-based), or low-quality carbohydrates like maltodextrin that can be difficult for the body to digest, leading to gas and discomfort.

For better digestion, mix your mass gainer with water or a plant-based milk instead of regular milk. You can also try using half water and half milk if you're not severely lactose intolerant. Using a blender to ensure a smooth, clump-free shake can also help.

If you experience a persistent upset stomach, consider reducing your dosage to a half-serving for a week to see if your body adapts. If symptoms continue even with adjustments, you should stop taking the product and consult a healthcare professional.

To prevent diarrhea, ensure you are properly hydrated, choose a lactose-free or plant-based gainer if you are lactose intolerant, and try taking smaller, more frequent doses rather than one large one.

Yes, it is common to experience some bloating, gas, or mild cramps during the first week as your digestive system adjusts to the new, high concentration of protein and carbohydrates.

Yes, there are mass gainers specifically formulated with lactose-free protein sources like whey isolate or plant-based proteins such as rice, hemp, or pea protein. Reading the ingredient list is crucial.

Yes, consuming a high-calorie shake too quickly can overwhelm your digestive system and is a common cause of gas, bloating, and stomach discomfort. It's best to sip it slowly over a period of 10 to 15 minutes.