How Many Calories Can You Burn Fasting for 24 Hours?

Have you ever skipped meals for a day and wondered, “Did I just torch a bunch of calories — or did I mainly lose water?” Picture this: it’s Monday, you decide to fast from dinner to dinner, and by the next evening you’re curious whether that 24-hour fast actually made a dent in your energy balance. Let’s break it down in practical, science-backed terms so you know exactly what to expect.

Introduction: What a 24-Hour Fast Really Does

Fasting for 24 hours is a popular intermittent fasting approach used for weight control, metabolic benefits, or simply as a reset. But the burning question that brings most people here is: how many calories can you burn fasting for 24 hours? The short answer is: roughly the same number of calories as your body would burn in a normal 24-hour period — your basal metabolic rate plus whatever activity you do — but the composition of those calories (fat vs. glycogen) and short-term water changes can make the scale look different.

How Calorie Burning Works During a 24-Hour Fast

BMR, Activity, and the Effect of Fasting

Your total calories burned in any 24-hour window equals:

• Basal Metabolic Rate (BMR) — energy to keep you alive (heart, lungs, brain)
• Non-Exercise Activity Thermogenesis (NEAT) — fidgeting, walking, standing
• Exercise activity — workouts or planned exercise
• Thermic Effect of Food (TEF) — energy to digest food (this drops during fasting)

During a 24-hour fast, TEF is essentially reduced because you’re not digesting a meal, which slightly lowers total daily calorie burn. But short fasts can also raise sympathetic tone (mildly) and increase fat oxidation, so the net difference in calories burned is usually small.

Real-World Example: How Many Calories You Might Burn

Example 1 — Sedentary female, 35 years old, 140 lb (63 kg), BMR ≈ 1,400 kcal/day: On a 24-hour fast she’ll burn roughly 1,400 kcal (BMR) + 200–400 kcal (NEAT) = ~1,600–1,800 kcal total.

Example 2 — Moderately active male, 30 years old, 180 lb (82 kg), BMR ≈ 1,800 kcal/day: With daily movement he might burn 1,800 kcal (BMR) + 400 kcal (activity) = ~2,200 kcal in that 24-hour fast.

These numbers are ballpark. The main takeaway: a 24-hour fast typically burns roughly a day’s worth of calories — not a dramatic multiplier.

Will a 24-Hour Fast Melt Fat or Just Water?

In the first 24 hours you’ll use stored glycogen, and with glycogen goes water (about 3–4 grams of water per gram of glycogen). That often shows as rapid weight loss on the scale, but much of it is water. True fat loss comes from sustained calorie deficits over time. However, a 24-hour fast can increase fat burning proportionally more than an eating day, especially once glycogen stores are lower.

Practical Tips: How to Maximize Benefits and Stay Safe

• Hydrate and include electrolytes — fasting increases fluid loss.
• Keep activity light to moderate — walking, mobility work, and gentle yoga are ideal.
• Avoid heavy resistance or maximal lifts if you’re new to fasting; performance can dip.
• Plan your refeed: focus on balanced meals with protein, fiber, and healthy fats.
• Track progress over weeks, not after a single 24-hour fast; long-term consistency matters.

Workout Variations for a 24-Hour Fast

Choose from these safe workouts based on energy levels:

• Low-intensity steady-state (LISS) cardio — brisk 30–60 minute walks
• Mobility and flexibility sessions — 20–30 minutes of yoga or stretching
• Light resistance training — bodyweight circuit or low-load strength work
• Short HIIT — only if you’re experienced with training fasted and feel strong

How Many Calories Can You Burn Fasting for 24 Hours? — The Bottom Line

So how many calories can you burn fasting for 24 hours? In most cases, you’ll burn roughly the same total calories as any other 24-hour period based on your BMR and activity level — typically between 1,200 and 3,000 kcal depending on your size and movement. A 24-hour fast shifts fuel use toward fat and reduces the thermic effect of food, but it doesn’t produce a dramatic spike in total calories burned.

Healthy Lifestyle Advice and Real-World Examples

If your goal is fat loss, combine periodic 24-hour fasts with a moderate calorie deficit on eating days and consistent exercise. For example, a 45-year-old woman who cycles 3x per week and does strength training twice weekly can use one 24-hour fast per week to help maintain discipline and support a weekly calorie deficit — but the weekly calorie balance will be the true driver of results.

If you’re training for performance, use fasting sparingly and avoid fasted heavy lifts. Many athletes use targeted nutrition strategies instead.

Frequently Asked Questions

1. Will I lose fat if I fast for 24 hours?

Yes, you may increase fat oxidation during a 24-hour fast, but meaningful fat loss requires a sustained calorie deficit over time. Think of a 24-hour fast as a tool, not a magic solution.

2. How much weight will I lose after a 24-hour fast?

Expect some immediate water weight loss from glycogen depletion and modest fat loss if you’re in a calorie deficit. Typical scale drops might be 1–3 pounds, but much of that can be water. Track body composition over weeks for real progress.

3. Can I exercise during a 24-hour fast?

Yes — light to moderate exercise is generally safe and can increase fat burning. For high-intensity or heavy strength sessions, gauge how you feel and consider scheduling those workouts on fed days to maintain performance and recovery.

Conclusion — Take Action with Purpose

Fasting for 24 hours can be a useful strategy for many people, but when asking “how many calories can you burn fasting for 24 hours,” remember that the answer depends on your BMR and activity level. A 24-hour fast typically burns roughly a full day’s worth of calories and shifts fuel use toward fat, but long-term results depend on consistent habits. Try combining occasional 24-hour fasts with sensible nutrition and the right workout plan — explore our workout routines and nutrition guides to create a balanced approach. For everyday balance, check our wellness tips.

Ready to experiment safely? Start with one supervised 24-hour fast, monitor how you feel, and adjust your training intensity. If you liked this deep dive, subscribe for more practical fitness strategies and smart fasting advice.