How Your Body Works When Intermittent Fasting: Understanding Energy and Blood Sugar Stability

Intermittent fasting (IF) has gained popularity for its ability to support weight management, enhance metabolism, and improve overall well-being. However, one common concern people have is whether their blood sugar will drop dangerously low when they are not eating. The truth is, when done correctly, intermittent fasting allows your body to regulate energy efficiently, ensuring stable blood sugar levels and optimal function.

How Your Body Uses Energy During Intermittent Fasting

When you follow an intermittent fasting routine, your body shifts through different energy sources in a structured and natural way. Here’s how it works:

1. The Fed State (Eating Window)

During your eating window, your body digests and absorbs nutrients from food. The primary energy source at this stage is glucose, which comes from carbohydrates. As you eat, glucose enters your bloodstream, prompting your pancreas to release insulin. Insulin helps transport glucose into your cells, where it is either used immediately for energy or stored as glycogen in your liver and muscles.

2. The Transition Phase (Post-Meal to Fasting Mode)

A few hours after eating, once your body has used up immediate glucose, it begins to tap into glycogen stores. Glycogen is a quick-access form of energy that can keep your blood sugar stable for several hours. This prevents sudden crashes and ensures your body continues to function normally.

3. The Fasting State (Burning Stored Energy)

As you continue fasting, usually after 10–12 hours, your glycogen stores start to deplete, and your body shifts to using stored fat for energy. This metabolic shift is called ketosis. During ketosis, fat is broken down into fatty acids and ketones, which serve as an alternative fuel source for the body and brain. Contrary to the myth that you “run out of energy,” your body actually becomes more efficient at using its own fuel reserves.

Why Your Blood Sugar Doesn’t Crash

Many people worry that fasting will cause their blood sugar to plummet, leading to dizziness, fatigue, or weakness. However, this isn’t the case for most people because:

• Glycogen Stores Act as a Buffer — Your body has enough stored glycogen to keep blood sugar stable for hours after eating.
• Fat Adaptation Ensures Energy Stability — When glycogen runs low, your body seamlessly switches to burning fat, providing a steady energy supply.
• Hormones Regulate Blood Sugar — Hormones like glucagon and cortisol help keep blood sugar levels from dropping too low, ensuring your brain and muscles receive the fuel they need.

The Benefits of This Natural Energy System

By allowing your body to work the way it was designed to, intermittent fasting can offer several advantages:

✅ Improved Insulin Sensitivity — Your body becomes more efficient at using insulin, reducing the risk of insulin resistance.
✅ Sustained Energy Levels — Without the blood sugar spikes and crashes caused by frequent eating, you feel more stable and energised.
✅ Fat Loss and Metabolic Health — Burning stored fat leads to natural weight loss and improved metabolic function.
✅ Better Mental Clarity — Ketones provide a clean, steady energy source for the brain, improving focus and cognitive function.

Final Thoughts

Intermittent fasting doesn’t leave you depleted — it allows your body to function efficiently, using stored energy in a way that aligns with how humans have evolved. Your blood sugar remains stable, and rather than “starving,” your body learns to become metabolically flexible, tapping into its reserves as needed.

When done correctly, IF supports balanced energy, better health, and a sustainable lifestyle. So, trust the process — your body knows exactly what to do!
contact Susan susan@intermittentfast.co.uk