How Much Weight You Should Expect to Lose on a 36-Hour Fast

Fasting has become a popular tool for weight loss, metabolic health, and longevity—but if you're eyeing a 36-hour fast, you’re probably wondering: How much weight can you actually lose in that time? The answer isn’t one-size-fits-all, but we’ll break it down based on science, real results, and what happens in your body during those 36 hours.

What Happens to Your Body During a 36-Hour Fast?

A 36-hour fast means you go from dinner one day to breakfast two days later without eating. During that time, your body goes through several phases:

• 0–12 Hours: Your body uses glucose (from your last meal) for energy.

• 12–24 Hours: Glycogen (your body’s stored form of carbohydrates) starts depleting, and fat-burning kicks in.

• 24–36 Hours: Your body shifts fully into fat metabolism, producing ketones for energy. Autophagy (your body’s cellular cleanup process) also ramps up.

This shift in fuel sources is why fasting can lead to rapid weight changes¹.

How Much Weight Can You Lose in a 36-Hour Fast?

The amount of weight you lose in 36 hours depends on several factors:

1. Water Weight Loss (1–5 Pounds)

The first thing your body burns through is glycogen, which holds onto water molecules. When glycogen is depleted, the water attached to it is flushed out, leading to rapid initial weight loss.

• The average person stores 500g of glycogen, which holds 3–4 times its weight in water.

• This means you could drop 2–5 pounds of water weight within the first day of fasting.

2. Fat Loss (~0.5 Pounds)

Once glycogen is depleted, your body turns to fat for energy. During a 36-hour fast, most people burn around 0.5 pounds of fat depending on:

• Metabolism – Higher metabolism = more fat burned.

• Activity level – Light activity during fasting burns extra calories.

• Body composition – Leaner individuals may lose less fat compared to those with higher body fat percentages.

3. Muscle Loss (Minimal, If Done Right)

Worried about muscle loss? Good news: A short-term fast won’t break down much muscle—especially if you stay active and consume enough protein in your meals before and after fasting.

• Studies show fasting increases human growth hormone (HGH), which helps preserve muscle while promoting fat loss.

• Strength training before your fast can further protect muscle mass.

Total Weight Loss Estimates

Important Note: Much of the initial weight loss is water, meaning it may come back once you eat again. However, the fat loss is real and can add up over multiple fasting cycles.

Can You Speed Up Fat Loss During a 36-Hour Fast?

If you want to maximize fat burning, here are a few tricks to optimize your fast:

• Stay hydrated – Drink plenty of water to support metabolism and fat breakdown. No amount of water will break your fast.

• Take electrolytes – Prevent dehydration and fatigue by supplementing with sodium, potassium, and magnesium.

• Stay lightly active – Walking or gentle yoga can enhance fat oxidation during a fast.
  Drink black coffee or tea – Caffeine may slightly boost fat-burning without breaking your fast. Remember - sugar, cream, and other coffee/tea additives will break your fast.

Support cellular function – Consider using biomimetic cell care to enhance metabolic benefits. (Learn more here)

What Happens After You Break Your Fast?

Once you eat again, some water weight will return, but if you break your fast using the tips below, you can extend the benefits of fasting beyond your actual fasting window.

Tips for Breaking a 36-Hour Fast:

• Start with protein & healthy fats – Eggs, avocado, or bone broth are great choices.

• Ease into carbs – Stick to whole, fiber-rich sources like sweet potatoes or quinoa.

• Avoid processed junk – High-sugar and processed foods can spike insulin and cause bloating.

By following a mindful refeeding approach, you’ll avoid bloating, energy crashes, and unnecessary weight regain.

Who Should (and Shouldn’t) Try a 36-Hour Fast?

A 36-hour fast may be ideal for:

• People looking for a metabolic reset or fat loss boost.

• Those interested in cellular health and longevity benefits.

• Individuals who are already comfortable with intermittent fasting and want to try something longer.

A 36-hour fast may not be best for:

• People with diabetes, eating disorders, or certain medical conditions.

• Pregnant or breastfeeding women.

• Individuals with high-intensity training schedules that require more frequent fueling.

Always check with a healthcare provider before making major dietary or lifestyle changes.

Final Thoughts: Is a 36-Hour Fast Worth It?

A 36-hour fast can lead to 1.5–5.5 pounds of weight loss, but keep in mind:

• Some of that is water weight, which may return after refeeding.

• You’ll likely burn ~0.5 pounds of fat, which adds up over time.

• You’ll experience additional health benefits like autophagy, insulin sensitivity, and metabolic flexibility.

If done correctly and paired with a healthy diet and lifestyle, a 36-hour fast can be a powerful tool for weight loss, fat burning, and overall well-being. 

Here’s what else you need to know about the benefits of a 36-hour fast.

References

¹ References ¹ Anton, S. D., Moehl, K., Donahoo, W. T., Marosi, K., et al. (2018). Flipping the metabolic switch: Understanding and applying the health benefits of fasting. Obesity, 26(2), 254-268.