Will exercise during fasting cause muscle loss?

When fasting, some people eat less than usual, reducing their intake of protein—the key building block for muscle. This can have two main consequences: If you’re not consuming enough calories, the body may break down both fat and muscle protein to meet its energy needs. Not getting enough protein during your eating window can further accelerate muscle loss, especially during prolonged fasting. Insufficient calorie intake can lead to low blood sugar, dizziness, and other symptoms that impair normal body function, ultimately resulting in muscle loss. Therefore, it’s important to maintain a balanced diet with enough protein to support muscle preservation. However, pairing intermittent fasting (IF) with high-intensity training like weightlifting or HIIT can help counter muscle loss. Regular strength training during fasting encourages your body to burn fat while preserving, or even building, muscle. So, even in a calorie deficit, combining IF with exercise can help you lose fat without sacrificing muscle mass.