Preserving Muscle on IF: How to Stay Strong While Losing Fat

The most common fear among gym-goers considering intermittent fasting is "catabolism"—the fear that their body will eat its own muscle for energy during the fasting window.

But the science tells a different story. If done correctly, intermittent fasting can actually help you achieve a "recomposition," where you lose body fat while maintaining (or even building) lean muscle mass.

Human Growth Hormone (HGH) to the Rescue

One of the fascinating metabolic responses to fasting is a significant spike in Human Growth Hormone (HGH). HGH is naturally muscle-sparing and fat-burning. By going for extended periods without food, you are creating a hormonal environment that actually protects your muscles while targeting fat cells.

The Two Pillars of Muscle Preservation

1. Protein Density during the Eating Window: Fasting isn't an excuse to under-eat. You still need to hit your daily protein targets (usually 1.6g to 2.2g of protein per kg of body weight). Because your eating window is shorter, each meal needs to be more protein-dense. Use the IMCAF Meal Analysis tool to track your protein across your meals and ensure you're hitting your goal.

2. Resistance Training: If you don't use it, you lose it. Your body needs a signal that the muscle is necessary. High-intensity resistance training (weightlifting, calisthenics) provides that signal.

When Should You Eat Protein?

Contrary to the "anabolic window" myths of the past, your total daily protein intake is more important than the exact timing. However, for most people, having a high-protein meal to "break" the fast is an excellent way to trigger muscle protein synthesis.

Myths vs. Reality

• Myth: "Fasting for more than 16 hours causes immediate muscle loss."
• Reality: Significant muscle breakdown (proteolysis) usually doesn't occur until much longer into a fast (24-48+ hours), and even then, only if your body fat is extremely low.

The IMCAF Advantage

Use the IMCAF BMR Calculator to determine your caloric needs and then ensure your Meal Logs show a sufficient percentage of calories coming from protein.

Fasting and strength are not enemies; they are two tools that, when used together, can transform your body composition.