Intermittent Fasting and Muscle Gain: Here’s What You Need to Know

Gaining muscle goes hand in hand with diet. We know that to build muscle, a consistent workout routine and a calorie surplus are essential. We also know that we need to eat enough protein, carbohydrates, and healthy fats for our muscles to grow (6).

So when you hear about intermittent fasting—an eating pattern that alternates between periods of eating and fasting—you may think it contradicts muscle gain. It must be hard to pack on muscle if you’re not eating all the time, right? Can you lean down and bulk up simultaneously?

Well, like most things in fitness, there’s more to it than meets the eye.

Here’s what we know about balancing intermittent fasting and muscle gain, and how you can potentially achieve your muscle-building goals with this approach.

Can You Gain Muscle While Intermittent Fasting?

You can gain muscle while intermittent fasting. The “lean gains” approach to intermittent fasting is a prime example of how building muscle and following an IF protocol can go hand in hand.

Lean gains was created by Martin Berkhan and involves fasting for 16 hours a day and eating during an 8-hour window. The idea is that you’ll hit your daily protein intake goal within that time frame (usually around 1 gram per pound of body weight) and still have enough calories to support muscle growth.

However, 16/8 fasting for muscle gain (or any other fasting regimen) may not work for everyone. Some people may struggle to consume enough calories and protein within the allotted window, which makes building muscle difficult.

So is it possible? Yes. Is it the best approach for everyone? Maybe not.

In a previous blog titled, Is Fasting Bad we emphasized the individuality of fitness. There’s no one-size-fits-all approach, and this is particularly true for intermittent fasting and muscle gain.

Does Intermittent Fasting Get Rid of Fat or Muscle?

As with all other weight loss methods, intermittent fasting typically results in a calorie deficit. When you’re in a calorie deficit, you burn more calories than you consume, and your body turns to stored energy (fat or muscle) for fuel. So yes, you may lose some fat and muscle while intermittent fasting.

Whether you lose more fat than muscle depends on various factors, including:

• Your fasting regimen – long, extended fasts may lead to more muscle loss while shorter, intermittent fasts may help preserve muscle mass.
• Your overall diet – if you’re not consuming enough protein and calories, you may experience more muscle loss than fat loss during intermittent fasting (8).
• Your activity level – regular exercise and resistance training can help maintain muscle mass while in a calorie deficit (8).
• Your body composition – individuals with a higher percentage of body fat generally lose more fat than muscle during a weight loss journey (1).

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Is Intermittent Fasting Good for Weight Lifting?

Intermittent fasting may be beneficial for weightlifting in some ways, including:

• Improved insulin sensitivity – intermittent fasting has been suggested to improve how efficiently the body uses insulin, which might help with muscle repair and growth (4).
• Increased human growth hormone (HGH) production – studies have suggested that fasting may cause an increase in HGH levels, which could be helpful for muscle building (3).
• Increased fat burn – intermittent fasting can help reduce body fat, which can make muscles appear more defined and prominent (5).

However, there are also potential drawbacks that should be considered:

• Possible muscle loss – as previously mentioned, prolonged or extreme fasting may lead to muscle loss.
• Potential for decreased performance – some individuals may experience a decrease in strength and energy levels when fasting, which can impact weightlifting performance.
• Difficulty meeting calorie and protein requirements – it may be challenging to consume the necessary amount of calories and protein within a limited time frame while intermittent fasting.
• Difficulty spreading protein intake – some experts recommend spreading protein intake evenly throughout the day for optimal muscle growth, but this can be challenging to achieve with intermittent fasting.

In our Intermittent Fasting Exercise blog, we discussed the importance of listening to your body and finding what works best for you. If intermittent fasting does not align with your workout routine or goals, it may not be the best approach for weightlifting.

Can I Lose Fat and Gain Muscle at the Same Time?

Losing fat and gaining muscle at the same time, aka body recomposition, is possible (1). However, it requires a balanced combination of diet and exercise that may be challenging to achieve with intermittent fasting. That being said, some individuals have successfully achieved body recomposition with intermittent fasting, so it’s not entirely out of the question.

Here’s how to prevent muscle loss during intermittent fasting, and potentially support muscle gain:

Start Slow and Steady

Research has shown rapid weight loss to be a surefire way to lose muscle. What tends to happen during rapid weight loss is a disproportionate amount of lean tissue and fat loss, compared to slow and steady weight loss (16). Therefore, if you’re trying to lose fat and gain muscle at the same time, it’s important to do it gradually.

First, you need to determine your maintenance calorie requirements and aim for a moderate calorie deficit of around 300-500 calories per day. This should allow for steady weight loss without sacrificing too much muscle.

During your eating window, aim to meet your calorie and protein goals. If you struggle to consume enough calories, consider incorporating high-calorie, protein-rich, nutrient-dense foods such as nuts, avocados, and fatty fish into your meals.

A protein intake of at least 0.7 -1 gram per pound of body weight per day is often recommended for preserving muscle mass during weight loss (6).

Secondly, decide on a sustainable fasting regimen. Start with shorter fasts and gradually increase the duration if desired. However, there’s a limit to how long you can fast before risking muscle loss, which leads to our next point.

Extended fasts (24 hours or more) may lead to significant muscle loss, whereas shorter fasts (16 hours or less) may be more manageable and potentially allow for muscle gain.

Your best bet is to keep your fasts between 12 and 16 hours for muscle gain and IF benefits.

Read more: Green Tea Intermittent Fasting: Benefits and Side Effects

Consider Supplementation

Getting all your required nutrients and protein within a limited time frame while intermittent fasting can be challenging. To make it easier, you could consider incorporating supplements into your routine.

Protein supplements such as whey or casein protein powders can help meet your daily protein goals within a short eating window (9). Other potentially beneficial supplements for muscle gain include creatine, BCAAs, and beta-alanine.

Many wonder whether taking supplements during a fast will break their fast. Supplements with a caloric value will technically break the fast and although their impact may be minimal, they may still affect your fasted state.

However, taking supplements during your eating window will not interfere with the benefits of intermittent fasting. Furthermore, some supplements such as creatine must be taken with food to be properly absorbed by the body.

Resistance Training Timing

Resistance training is essential for maintaining or increasing muscle mass while intermittent fasting. Regular strength training exercises such as weightlifting can help preserve muscle and support muscle growth (10).

However, you may want to consider timing your resistance training sessions during your eating window. This way, you can consume carbohydrates, protein, and other nutrients shortly after working out, which can help with muscle repair and growth (14). Consuming a carbohydrate-rich meal before your workout can also help give you the energy to power your workout, particularly if it’s high-intensity.

Many consider fasted exercise, including weightlifting, to be beneficial for fat loss. There’s not enough research to support this claim, but some individuals may prefer working out in a fasted state. If this is the case for you, consider scheduling your workouts toward the end of your fasting period so you can consume protein and other nutrients shortly after.

Weightlifting principles such as progressive overload, consistency, and proper form still apply when intermittent fasting.

Stay Consistent

Consistency is key for achieving any fitness goal, including body recomposition. This means sticking to your intermittent fasting schedule and maintaining a consistent exercise routine.

If you find yourself regularly skipping meals or workouts, it may be challenging to see progress with muscle gain when intermittent fasting. Therefore, you must ensure you plan your eating window and workout schedule accordingly.

In addition, listen to your body and make any adjustments as required. If you feel weak or fatigued during a fasted workout, it may be best to break your fast earlier to support your performance.

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FAQs

• Will I lose muscle if I intermittent fast?

It’s possible to lose muscle if you don’t consume enough protein or calories while intermittent fasting. This is the case with all weight loss methods, not just intermittent fasting. However, with proper nutrition and exercise, it’s possible to preserve or even gain muscle while intermittent fasting.

• Does fasting increase testosterone?

Fasting may have the potential to influence testosterone levels, particularly through mechanisms such as improved insulin sensitivity and weight loss. However, the effects can differ widely based on the type and duration of fasting and individual differences.

Mechanisms that may contribute to increased testosterone levels during fasting include:

• Insulin sensitivity: Fasting has been suggested to improve insulin sensitivity, which may be linked to better hormonal health, including testosterone production (11).
• Weight loss: Reduction in body fat from fasting can decrease aromatase activity, an enzyme that converts testosterone to estrogen, potentially increasing free testosterone levels (15).

The impact of fasting on testosterone can vary based on individual factors such as:

• Duration: Short-term vs. long-term fasting
• Nutritional status: Adequate micronutrient intake
• Exercise: Physical activity levels
• Body composition: Baseline body fat percentage
• Metabolic health: baseline insulin sensitivity

Long-term fasting

The effects of long-term fasting on testosterone are more complex. Prolonged caloric restriction can lead to reduced energy availability, potentially lowering testosterone levels over time. This is because sufficient energy and nutrient intake are essential for maintaining hormonal balance (7).

Exercise and nutrition

Intensive exercise can stimulate testosterone production, particularly when paired with a protein-rich diet. Eating right and getting enough rest and recovery are essential for supporting testosterone levels while intermittent fasting (17).

• Does fasting 16/8 cause muscle loss?

16/8 intermittent fasting, when done correctly, should not cause muscle loss as long as you consume enough calories and protein during your eating window to support muscle growth and repair (14). Furthermore, incorporating resistance training into your routine can help preserve or even increase muscle mass when intermittent fasting.

• Will a protein shake ruin intermittent fasting?

A protein shake will break your fast, but consuming one during your eating window should not affect the benefits of intermittent fasting. If you’re following a specific fasting protocol for health or weight loss purposes, you should consider choosing a supplement without excessive calories and consume it during your eating window. This is because a shake contains calories, and even minimal caloric intake can break a fast.

The Bottom Line

Losing fat and gaining muscle at the same time is possible, but it requires a balanced combination of diet, exercise, and consistency. While intermittent fasting may not be the most optimal approach for achieving body recomposition, it is possible to make it work with the right strategies in place. 

Remember to start slow and steady, consider supplementation, time your resistance training sessions appropriately, and stay consistent with your routine. Always listen to your body and adjust as needed for optimal results.