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How to Fast Without Losing Muscle: Prevent Weakness & Maintain Strength!

Intermittent fasting (IF) has become one of the most popular diets for weight loss, longevity and overall health, but many people worry about fasting and muscle loss.

The good news? With the right strategies, you can maintain, and even build, muscle while fasting. 

In this blog, we’ll break down the science, provide practical tips and answer common questions like ‘how to prevent muscle loss when fasting’ and ‘does fasting lose muscle?’

Products mentioned in this blog:

• Protocol X
• LPC Neuro

Jump there now:

• Does Fasting Cause Muscle Loss?
• How to Prevent Muscle Loss When Fasting
• Can You Build Muscle While Fasting?
• Should You Exercise While Fasted?
• 3 Tips for Maintaining Muscle While Fasting

Does Fasting Cause Muscle Loss?  

The short answer: No, fasting does not inherently cause muscle loss. Muscle loss can occur, however, if you’re not careful with your diet and exercise routine.  

What the Research Says:  

• Weight Loss and Lean Mass: When you lose weight, some of that loss typically comes from lean mass (which includes muscle). Studies show that intermittent fasting results in similar muscle loss as other diets — around 1 kg (2 pounds) over several months, although, some studies show no significant loss of lean mass at all. A review comparing intermittent fasting and traditional dieting found that intermittent fasting preserved more lean mass despite calorie restriction.
• Protein and Exercise Matter: Research suggests that maintaining adequate protein intake and engaging in regular strength training can help preserve muscle during fasting.  A study on alternate-day fasting and cycling workouts found that 25–40 minutes of exercise three times per week maintained muscle mass. An 8-week study on resistance training and time-restricted eating also showed no muscle loss, while fat mass decreased significantly.
• Fasting and Muscle Gain: While fasting may not be the best method for building muscle, it’s still possible to maintain strength and muscle mass if you follow the right strategies.  

Further Reading: All About Muscles and Longevity

How to Prevent Muscle Loss When Fasting  

As for how to fast without losing muscle, here are science-backed strategies to help you maintain muscle and strength while fasting:  

1. Focus on Your Protein Intake

Protein is the building block of muscle as, if you don’t have enough protein, your body may end up breaking down muscle tissue for energy.  

How Much Protein Do You Need? Aim for 0.7–1 gram of protein per pound of body weight per day (1.6–2.2 grams per kilogram). For example, if you weigh 150 pounds (68kg), aim for 105–150 grams of protein daily. This depends on what you’re trying to achieve though.

Further Reading: How Much Protein Do I Need As I Age?

Timing Matters: Spread your protein intake across your eating window. Research shows that consuming protein regularly throughout the day supports muscle maintenance.  

Protein-Rich Foods: Include eggs, chicken, fish, tofu, legumes and dairy in your meals. If you struggle to meet your protein needs, try taking a protein supplement like whey or plant-based protein powder.  

2. Strength Training is Incredibly Important

As for how to prevent weakness when fasting, exercise, especially resistance training, is important for maintaining muscle mass. A study found that men who combined intermittent fasting with weight training maintained their lean mass and even lost fat.  

Why It Works: Strength training tells your body to preserve muscle, even in a calorie deficit.  

How Often? Aim for 2–3 strength-training sessions per week, focusing on compound movements like squats, deadlifts, push-ups and rows.  

3. Avoid Severe Caloric Deficits

Losing weight too quickly can lead to muscle loss.  

Ideal Rate of Weight Loss: Aim to lose 0.5–2 pounds (0.2–0.9 kg) per week. This slower rate helps preserve muscle.  

Mindful Eating: Focus on nutrient-dense foods during your eating window to ensure you’re getting enough calories and nutrients.  

4. Consider Taking Supplements

Certain supplements can support muscle maintenance during fasting. For example:

• Creatine: This supplement helps improve strength and muscle mass, especially when combined with resistance training. Take it during your eating window.  
• BCAAs (Branched-Chain Amino Acids): While not necessary, BCAAs may help reduce muscle breakdown during fasting periods. Just remember that they’re not a substitute for adequate protein intake.  
• Protein Powder: Helps meet daily protein needs if food intake is insufficient.
• Protocol X: Helps to improve your cognitive health, vitality and overall anti-ageing needs with its mix of 20+ science-backed longevity ingredients. 
• LPC Neuro: Fasting can be a longevity strategy, so to help improve your brain and cognitive health, consider taking the most advanced form of omega-3 that actually crosses the blood-brain barrier.

Can You Build Muscle While Fasting?  

Building muscle while fasting is possible but challenging. The reason for this?  

• Caloric Surplus Needed: To build muscle, you need to take in more calories than you burn. Fasting can make it harder to meet this surplus, especially if you’re eating nutrient-dense, filling foods.  
• Protein Timing: Intermittent fasting may limit your ability to spread protein intake throughout the day, which is best for muscle growth.  

Just know that if you’re consistent with your protein intake and strength training, you can still make progress.  

Further Reading: How Muscles Impact Metabolism

Should You Exercise While Fasted?  

Exercising while fasted is a personal choice. Here’s what the science says:  

• Weight Loss: Fasted and non-fasted exercise lead to similar fat loss and muscle preservation.  
• Performance: Fasted exercise may impair performance, especially for high-intensity or endurance activities.  
• Recovery: If you exercise fasted, try to eat 20+ grams of protein shortly after your workout to support muscle recovery.  

3 Tips for Maintaining Muscle While Fasting  

1. Stay Active: Incorporate both strength training and aerobic exercise into your routine. Aim for 150 minutes of moderate activity or 75 minutes of vigorous activity per week.  
2. Avoid Yo-Yo Dieting: Rapid weight loss and gain can lead to muscle loss over time. Focus on sustainable habits.  
3. Eat High-Quality Foods: Fill your eating window with minimally processed nutrient-dense foods to support muscle health.  

Further Reading: Does Menopause Affect Your Muscles

End Note

Fasting doesn’t have to mean losing muscle. By making sure you get enough protein, stay active, and avoid extreme calorie deficits, you can maintain — and even build — muscle while fasting. Whether you’re following a 16:8 intermittent fasting schedule or observing religious fasts like Ramadan, these strategies can help you stay strong and healthy.  

Remember, fasting is just one tool in your health toolkit. Pair it with a balanced diet, regular exercise, and mindful eating for the best results.  

Keep an eye out for our upcoming Recovery Electrolyte supplement to help you recover the electrolytes and minerals you deplete and miss out on during fasting!

Products mentioned in this blog:

• Protocol X
• LPC Neuro