How Many Calories Can You Burn Fasting for 24 Hours? A Realistic Breakdown

Ever wondered if skipping food for a day will torch calories the way the latest trend promises? Imagine you’re heading into a 24-hour fast before a weekend trip — will you really burn through fat, or mostly just feel hungry? In this article I’ll walk you through exactly how many calories you can burn fasting for 24 hours, explain the science in plain English, and give practical tips and workouts so you get results without guessing.

What actually happens to your body during a 24-hour fast?

When you fast for 24 hours, your body shifts fuel sources and hormonal signals change: insulin drops, glucagon and catecholamines rise, and your body increases fat oxidation. But “fat burning” and “calorie burning” aren’t the same thing. Your total calories burned during a 24-hour fast will mostly equal your usual daily energy expenditure (your BMR plus activity), with small short-term shifts in substrate use (more fat, less carbohydrate).

Key components of energy burn

• BMR (Basal Metabolic Rate): Energy used for breathing, circulation, cell function — the largest piece of the daily burn.
• NEAT (Non-Exercise Activity Thermogenesis): Fidgeting, walking around, chores.
• Exercise: Burn from workouts — variable depending on intensity and duration.
• TEF (Thermic Effect of Food): Energy used to digest food — this drops to near zero while fasting.

How to estimate how many calories you can burn fasting for 24 hours

The simplest way to estimate is to calculate your normal daily calorie burn (TDEE). If you fast for 24 hours you generally still burn roughly that amount — minus the thermic effect of food you would have had if you ate. Short-term (one day) fasting does not dramatically increase calorie burn for most people.

Practical estimation (examples)

Here are three real-world examples to make it concrete:

• Average sedentary woman (approx. 140 lb / 63 kg): BMR ~1,350 kcal/day, TDEE ~1,600 kcal/day. In a 24-hour fast she’ll burn roughly 1,550–1,650 kcal depending on activity — a 24-hour fast may remove ~100–200 kcal of TEF compared to an eating day.
• Moderately active man (approx. 180 lb / 82 kg): BMR ~1,800 kcal/day, TDEE ~2,400 kcal/day. Expect roughly 2,200–2,400 kcal burned during a 24-hour fast.
• Active athlete (heavy training): BMR ~2,000+ kcal/day, TDEE can be 3,000+ kcal/day. If you train during the fast you’ll burn more — the fast itself doesn’t add large extra burns, your workouts do.

Bottom line: most people burn roughly their usual daily calories during a 24-hour fast. The net calorie deficit from the fast comes mostly from the calories you didn’t eat, not an explosion of extra energy expenditure.

Factors that influence calorie burn during a 24-hour fast

• Body size & composition: Larger bodies and more lean mass burn more calories at rest.
• Activity level: More movement or a hard workout raises caloric burn significantly.
• Age & sex: Metabolic rate declines with age; men typically have higher BMR.
• Fasting experience: People adapted to intermittent fasting may tolerate fasted workouts better and maintain activity levels.

Safe and effective fasted workouts

If your goal is to maintain muscle and increase fat loss efficiency while doing a 24-hour fast, choose workouts wisely.

Best workouts during a 24-hour fast

• Light cardio: Walking, easy cycling — burns calories and is low stress.
• Resistance training: Moderate weight lifting helps preserve muscle. Shorter sessions (30–45 min) are ideal.
• High-intensity intervals (short): 10–15 min HIIT can be done by experienced individuals, but listen to your body.
• Mobility and yoga: Great for recovery, stress control, and maintaining NEAT without heavy energy demand.

A sample fasted workout: 20–30 minutes brisk walk + 20 minutes full-body resistance circuit (bodyweight or light dumbbells). Finish with stretching.

Practical fitness tips and lifestyle advice for fasting days

• Stay hydrated — water, mineral water, and non-caloric electrolytes to maintain energy and prevent lightheadedness.
• Avoid heavy lifting if you feel weak — opt for technique-focused or lighter sessions.
• Prioritize sleep and stress management — poor sleep raises cortisol and can blunt benefits of fasting.
• Plan your refeed: break the fast with protein, fiber, and healthy fats to minimize overeating.
• Track progress over weeks — one 24-hour fast is a data point, consistent habits matter more for fat loss.

Real-world example: fasting for weight control

Jess (32, 150 lb) tried a 24-hour fast twice a week while keeping her usual workouts (3 days resistance, 2 days cardio). She noticed a modest weekly calorie deficit equal to the meals she skipped, maintained muscle, and found it easier to control overall weekly calories. The fasting days themselves didn’t create rapid metabolic boosts; they simplified her calorie control.

Frequently Asked Questions

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

You can create a calorie deficit with a 24-hour fast which will lead to fat loss over time if your weekly calories remain below maintenance. The fast itself typically shifts fuel toward fat, but long-term fat loss depends on consistent calorie balance and activity.

2. Can I exercise while fasting for 24 hours?

Yes — light to moderate exercise is generally safe and can help conserve muscle if you include resistance work. High-intensity or long endurance sessions are better after eating unless you’re well adapted to fasted training.

3. How many pounds will I lose fasting for 24 hours?

Short-term weight loss after a 24-hour fast is often water weight and glycogen loss. Expect modest scale drops (1–3 lb) that can return after refeeding. Sustainable fat loss comes from consistent calorie deficits over weeks and months.

Conclusion — what you should take away

So, how many calories can you burn fasting for 24 hours? In most cases, you’ll burn roughly your normal daily calories (your TDEE) during a 24-hour fast. The real calorie savings come from the meals you skip, not a dramatic metabolic increase. Use short fasts as a tool for simplifying calorie control, combine them with smart workouts (see our workout routines), and lean on good recovery and nutrition strategies (check our nutrition guides) to get results. If you want more sustainable habits, explore our wellness tips for sleep, stress, and long-term planning.

Ready to try a 24-hour fast safely and effectively? Start with a light workout plan, hydrate, and track how your body responds — then adjust. Share your experience or ask questions below and let’s make your plan realistic and enjoyable.