Can muscle mass be built while fasting and performing resistance training for a week?

From the Guidelines

It is not recommended to attempt to build muscle mass while fasting and performing resistance training for a week, as this can lead to muscle loss and other negative health effects.

Key Considerations

• Fasting can cause a decrease in muscle protein synthesis, which is essential for building and repairing muscle tissue 1.
• Resistance training without adequate nutrition can lead to muscle damage and decreased performance.
• A study found that just seven days of bedrest resulted in a 1 kg loss of lean leg muscle mass in older adults, highlighting the potential for rapid muscle loss during periods of reduced activity or fasting 1.

Nutrition Recommendations

• If attempting to build muscle while fasting, it's crucial to ensure you're getting enough protein during your eating window, aiming for 1.6-2.2 grams of protein per kilogram of body weight.
• Consider supplements like essential amino acid (EAA) mixtures or beta-hydroxy-beta-methylbutyrate (HMB) to help reduce muscle damage and support muscle growth 1.

Important Notes

• The metabolic response to fasting and resistance training is complex, and individual results may vary.
• Prioritizing a balanced diet that includes adequate calories and protein is generally advised to support muscle growth and overall health.
• It's essential to weigh the potential benefits and risks of fasting and resistance training, particularly for older adults or those with pre-existing health conditions, and consider consulting with a healthcare professional before starting any new regimen.

From the Research

Muscle Mass and Fasting

• The effect of fasting on muscle mass is a topic of interest, with some studies suggesting that it may be counter-productive to optimizing muscle protein turnover and net muscle protein balance 2.
• However, other studies have found that short-term intermittent fasting does not lower rates of muscle protein synthesis compared to continuous energy restriction or an energy balanced diet with matched protein intake 3.
• A study on healthy men found that a 10-day fast decreased body weight by 7% and basal metabolic rate by 12%, with fat mass and lean soft tissues accounting for about 40% and 60% of weight loss, respectively 4.
• Another study found that intermittent fasting reduced mouse body fat while maintaining muscle mass by regulating protein synthesis and autophagy 5.

Resistance Training and Fasting

• A study on the effect of fasting on indicators of muscle damage found that fasting did not robustly inhibit the signs and symptoms of exercise-induced muscle damage, but may generally affect common indirect markers of muscle damage 6.
• The study also found that the fasting group's loss of elbow extension was less than the post-prandial group, suggesting that fasting may have some beneficial effects on muscle function 6.
• However, the current evidence is limited, and more research is needed to fully understand the effects of fasting and resistance training on muscle mass and function 2, 3, 4, 5, 6.

Key Findings

• Fasting may not be optimal for building muscle mass, as it can lead to a decrease in muscle protein synthesis and an increase in muscle breakdown 2.
• However, short-term intermittent fasting may not have a significant impact on muscle protein synthesis, and may even have some beneficial effects on muscle function 3, 6.
• The effects of fasting on muscle mass and function may depend on the duration and type of fast, as well as the individual's overall diet and training program 4, 5.