What Supplements Cause Weight Gain? Exploring the Science

October 29, 2025 •

4 min read

A 2022 review of research highlights that gaining lean muscle mass is possible with supplements combined with a high-calorie diet and resistance training. So, what supplements cause weight gain, and how do they work to help you achieve your goals effectively?

Quick Summary

Supplements like mass gainers, creatine, and protein powders can aid weight gain by increasing calorie intake or muscle mass. Other factors, such as correcting nutrient deficiencies or taking excessive B vitamins, can also contribute to changes in body weight through metabolic effects.

Key Points

Mass Gainers: These high-calorie supplements provide a large number of calories from protein, carbs, and fats to create a necessary calorie surplus for weight gain.
Protein Powders: Used to increase overall protein intake, they primarily aid in building lean muscle mass, contributing to weight gain when paired with strength training.
Creatine: This supplement increases water content in muscle cells and boosts strength, leading to weight gain in both water weight and muscle mass.
Excess B Vitamins: Studies suggest that excessive intake of certain B vitamins, often from fortified foods, can promote fat synthesis and insulin resistance, indirectly contributing to weight gain.
Indirect Contributors: Other supplements, such as Omega-3s, can add healthy fat calories, while correcting deficiencies in vitamins like B1 can restore appetite.
Balanced Approach: Supplements are most effective when combined with a balanced diet and regular resistance training, rather than relied upon exclusively.

For most individuals, weight gain comes down to a fundamental principle: consuming more calories than your body expends. This is known as a caloric surplus. While a whole-foods diet is the cornerstone of healthy weight gain, certain supplements can provide a convenient and concentrated way to boost calorie and nutrient intake. Understanding the specific supplements and their mechanisms is key to achieving your desired results, whether that's building muscle or restoring a healthy body weight.

High-Calorie Mass Gainers

Mass gainers are perhaps the most direct answer for those wondering what supplements cause weight gain. These products are specifically formulated to provide a large number of calories in a single serving, making it easier for individuals with high metabolic rates or poor appetites to meet their energy needs. They are essentially a blend of macronutrients, typically containing high amounts of carbohydrates and protein, with varying levels of fat.

How Mass Gainers Function

The primary mechanism of a mass gainer is simply volume and convenience. Instead of trying to eat a large, full meal, you can drink a shake that packs hundreds, or even over a thousand, calories. This helps create the necessary calorie surplus to drive weight gain. Quality mass gainers will use complex carbohydrates like oats and quinoa powder for sustained energy, while lower-quality versions may rely on simple sugars, which can cause energy crashes and lead to unhealthy fat accumulation.

Protein Powders for Muscle Mass

Protein is essential for muscle building, and while not as calorie-dense as mass gainers, protein supplements play a crucial role in promoting weight gain in the form of lean muscle mass. This is particularly relevant when combined with a consistent strength training routine.

The Different Types of Protein

Protein powders come in several varieties, each with unique absorption rates and benefits:

Whey Protein: A fast-digesting protein, ideal for post-workout recovery when muscles are most receptive to nutrients.
Casein Protein: A slow-digesting protein that provides a sustained release of amino acids, making it a good choice before bed.
Plant-Based Proteins: Options like pea, hemp, and rice protein offer complete amino acid profiles for those with dietary restrictions.

Creatine and Water Retention

Creatine is one of the most studied and effective supplements for increasing muscle mass and strength. Its effect on weight gain is twofold: it increases water retention in muscle cells and, over time, promotes greater muscle growth through improved workout performance.

The Mechanics of Creatine-Related Weight Gain

When you supplement with creatine, it increases the water content within your muscle cells. This cellular swelling is part of the initial weight gain phase. However, by improving your strength and power output during workouts, creatine allows you to push harder and stimulate more muscle protein synthesis, leading to a long-term increase in lean muscle mass.

Indirect Contributors to Weight Gain

While some supplements are directly intended for weight gain, others can influence it indirectly. This is often the case with certain vitamins and minerals, where a deficiency can hinder appetite or metabolism, and correcting it can restore healthy function.

B Vitamins: Excess intake of certain B vitamins, particularly from fortified foods, has been linked in some studies to increased fat synthesis and insulin resistance, which can contribute to obesity. However, it is also true that a deficiency in B1 (thiamine) can cause loss of appetite and weight loss. Correcting a deficiency in B vitamins may therefore restore a normal appetite and lead to weight gain.
Omega-3 Fatty Acids: Often found in fish oil supplements, omega-3s don't directly cause weight gain but can contribute to overall health. When combined with a calorie surplus, they add healthy fat calories to your diet.

The Surprising Link to Excess Vitamins

Scientific reviews have explored how excessive consumption of fortified B vitamins, especially in developed countries with widespread food fortification, might be a factor in rising obesity rates. The mechanism is complex but involves potential increases in fat synthesis and interference with insulin signaling.

Supplements for Weight Gain: A Comparison Table


Supplement	Primary Mechanism	Type of Weight Gain	Key Considerations
Mass Gainers	High-calorie blend for caloric surplus	Muscle and fat	Choose quality carbs over simple sugars
Creatine	Increases water retention and strength	Water and lean muscle	Initial weight gain is water; sustained use builds muscle
Protein Powder	Supports muscle protein synthesis	Lean muscle	Must be combined with exercise and sufficient calories
Excess B Vitamins	Can promote fat synthesis (complex)	Fat	Typically an unintended side effect, not a primary goal

Cautions and Considerations

As with any dietary supplement, the use of weight gain aids is not without potential risks. It's crucial to approach supplementation with a balanced diet and regular exercise. Over-relying on high-calorie supplements without physical activity can lead to unhealthy fat accumulation rather than muscle growth. Potential side effects can include digestive issues, especially with high-protein or high-carb formulas, and possible allergic reactions. Always consult a healthcare professional or registered dietitian before starting a new supplement regimen, especially if you have pre-existing health conditions.

Conclusion

For individuals looking to increase their body mass, specific supplements like mass gainers, creatine, and protein powders can be effective tools. Mass gainers offer a high-calorie boost, while creatine and protein target muscle growth directly. It is important to remember that these supplements work best when integrated into a healthy, calorie-surplus diet combined with resistance training. Additionally, awareness of the indirect effects of vitamins and other nutrients is crucial for a holistic understanding of weight management. Always prioritize a balanced approach and seek professional guidance to ensure both safety and effectiveness on your weight gain journey.

Frequently Asked Questions

No, multivitamins do not directly cause weight gain as they contain negligible calories. However, correcting a vitamin deficiency can restore a healthy appetite, which might lead to weight gain if you were previously underweight.

Creatine causes weight gain in two ways: initially, by increasing the water content within your muscle cells, and over time, by helping you build more muscle mass by enhancing workout performance.

Some lower-quality mass gainers can be high in simple sugars, but high-quality options use complex carbohydrates and balanced macronutrient profiles to provide sustained energy for healthy weight gain.

Yes, for individuals with certain deficiencies, like Vitamin B1 (Thiamine), correcting the deficiency can help restore a healthy appetite that may have been suppressed, leading to healthy weight gain.

Protein powder is highly effective for gaining lean muscle mass, which contributes to overall body weight. It works best when combined with a sufficient calorie surplus and resistance training.

Potential side effects can include digestive issues like bloating, gas, and diarrhea, especially with excessive intake. Over-reliance can also lead to unhealthy fat gain rather than muscle, and some products may contain allergens.

Supplement-related weight gain, when done correctly, often involves an increase in lean muscle mass and intramuscular water. Fat gain is the accumulation of adipose tissue. Combining supplements with exercise helps direct the weight gain towards muscle.