Dr. Berg’s Healthy Keto and Intermittent Fasting Podcast

What Happens If You Don’t Eat For 5 Days?

22 snips

Aug 14, 2025

Discover what happens in your body during a five-day fast! Learn how glycogen is depleted on day one and how insulin drops, allowing fat reserves to be tapped. Day two brings deeper ketosis and begins the process of autophagy, recycling damaged proteins. By day three, brain function peaks, and the immune system resets, alongside a growth hormone surge. Hunger dissipates by day four, maximizing fat burning. Get insights on the benefits of electrolytes, nature walks, and bone broth to enhance your fasting experience!

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INSIGHT

Day One: Glycogen Loss And Fat Shift

Glycogen stores deplete within the first day, releasing large amounts of water weight because each glucose binds water.
Insulin drops quickly, flipping the body from sugar burning to fat burning as primary fuel.

ADVICE

Supplement Electrolytes During A Fast

Take electrolytes like sea salt, potassium, magnesium, and calcium to prevent cramps, fatigue, and lightheadedness.
Also consider trace minerals and B vitamins if you lack nutrient reserves before a prolonged fast.

ADVICE

Allowed Drinks And What To Avoid

Drink calorie-free beverages like black tea, black coffee, or water with a little lemon while fasting.
Avoid cream, sugar, artificial additives, and avoid apple cider vinegar due to added acidity.

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On day 1 of fasting, glycogen is eliminated from the body. Your insulin drops on your first day of fasting, allowing you to tap into your fat reserve.

Electrolytes, trace minerals, and B vitamins can be very beneficial during prolonged fasting, especially if you haven’t built up a reserve of these nutrients. You can drink tea and coffee without cream or sugar and have water with lemon during your 5-day fast. Plenty of sun, long walks in nature, hot and cold therapy, and HIIT can also enhance the benefits of prolonged fasting.

On day 2 of prolonged fasting, you get deeper into ketosis, which means your body burns fat for energy. Autophagy typically begins on the second day of prolonged fasting. This is the process in which the body recycles damaged proteins and uses them for fuel and new tissues.

On day 3, brain function and mood continue to improve. BDNF is stimulated, which helps support brain cell regeneration and increases your learning capacity.

You also enter a state of deep autophagy, which helps repair mitochondrial damage and clean up intracellular pathogens. On day 3 of a prolonged fast, your immune system essentially resets.

Prolonged fasting supports the growth of the thymus gland and allows the gut lining to regenerate completely. People often experience a massive spike in growth hormone on day 3, which protects against muscle loss.

On day 4, hunger is gone, and maximum fat burning occurs! Bone broth can be beneficial if you’re struggling through a 5-day fast or experiencing a stressful event.

Longevity and protective genes are heightened, and your antioxidant networks are strengthened during prolonged fasting. It can also help diversify your microbiome.

Slowly begin the refeeding process with around ¼ of your typical calories. Try an egg with sauerkraut, and then wait a few hours before consuming something like a small amount of soup with avocado. After a few more hours, consume berries and nuts. Wait before introducing a full meal and avoid sugar and carbohydrates. High-quality food is vital at this time!

After a 5-day fast, your skin, muscles, joints, and brain will show significant improvements! Regular intermittent fasting can help prepare you for a 5-day fast.

Dr. Eric Berg DC Bio:Dr. Berg, age 60, is a chiropractor who specializes in Healthy Ketosis & Intermittent Fasting. He is the Director of Dr. Berg Nutritionals and author of the best-selling book The Healthy Keto Plan. He no longer practices, but focuses on health education through social media.