You’ve chosen intermittent fasting (IF)–a focused approach in pursuit of better health, improved metabolism, and more mindful eating. Now you might be wondering: should you introduce exercise into your routine, and if so, when and how does it fit best alongside your fasting plan?
Here’s the good news. Many people find that a well-structured exercise routine can complement IF, no matter when you choose to work out–whether that’s during your fasting window or after you’ve broken your fast. The real value comes not from rigid rules about when to exercise, but from balancing your unique schedule, energy levels, and recovery needs.
In this guide, you’ll see the benefits of working out while fasting and how to do it sustainably.
The phrase “working out while fasting” can mean many different things.
Often, the term means “fasted training”–exercise performed in the fasted state, typically before your first meal of the day.
In this context, your body relies more on stored energy sources, like glycogen and fat, because insulin and blood sugar levels are lower (1).
However, “working out while fasting” can also mean exercising while practicing Intermittent Fasting. This term can mean working out at any point during your designated fasting window, including lighter activity later in the day or structured sessions closer to your planned fast break.
Some people find they feel best saving exercise for just after their first meal, using food to fuel and recover from the workout, while still aligning their schedule with intermittent fasting.
The short answer is yes, you can work out while fasting. However, the “how” and “how much” depend entirely on your goals, experience level, and the type of fasting you practice.
Our bodies are evolutionarily adapted to perform physical activity without a constant stream of food (2). Our ancestors didn’t have pre-workout snacks; they often hunted and gathered while fasting. Physiologically, your body can mobilize stored energy to fuel movement (3).
That said, context matters. A light jog or a moderate weightlifting session is very different from a high-intensity interval training (HIIT) class or a 2-hour competitive sports match.
If your primary goal is general fitness, metabolic flexibility, or fat loss, training in a fasted state is generally safe and effective for most people.
If your goal is peak athletic performance–like hitting a new personal record on a deadlift or sprinting at maximum velocity–you might find that a complete lack of carbohydrates hinders your top-end power output (4).
Ultimately, working out while fasting is a tool. Like any tool, it works best when applied to the right job.
If you wish to free yourself from all the extra pounds that have been weighing you down for way too long, start using the BetterMe: Health Coaching app and overhaul your entire life!
Combining exercise with fasting isn’t just about calorie restriction; it triggers unique metabolic adaptations that enhance your long-term health and fitness.
Here is what the available research says about the potential benefits of exercise while fasting:
One commonly discussed potential benefit is a shift toward using more fat for fuel. In lower-insulin periods (such as between meals), the body may rely more on stored energy sources.
Studies suggest that fasted exercise can result in higher fat oxidation during the workout than fed exercise (5, 6).
While this doesn’t automatically guarantee greater long-term weight loss (which is driven by total energy balance), it may improve your body’s ability to utilize fat as fuel–a trait known as metabolic flexibility (7).
Insulin resistance is a precursor to type 2 diabetes and a host of metabolic issues (8).
Both fasting and exercise can independently improve insulin sensitivity (9, 10). When combined, these practices may have a synergistic effect.
By draining muscle glycogen stores through exercise while insulin is already low from fasting, you create a powerful signal for your muscles to soak up glucose efficiently once you do eat (11). This effect may be particularly beneficial for those managing blood sugar levels.
Autophagy is the body’s cellular cleanup process, where cells recycle waste components and repair themselves (12).
Fasting stimulates autophagy (13).
Exercise also stimulates autophagy (14).
Doing them together may amplify this effect, potentially aiding cellular longevity and health (15). However, human research in this area is still evolving and has not yet quantified the exact magnitude of the boost.
Fasting can spike the secretion of Human Growth Hormone (HGH), which plays a vital role in muscle preservation and fat metabolism (16). Exercise is also a potent stimulus for HGH (17).
Training while fasted may create a hormonal environment–high HGH, low insulin–that favors the preservation of lean tissue while mobilizing fat stores, provided you consume adequate protein during your feeding window (18).
For those interested in diving deeper into the nuances of timing, you can read more about intermittent fasting and working out.
Read more: Is Fasting for 18 Hours the Sweet Spot for Improved Wellness?
Not all workouts are the same, especially when there’s limited fuel.
Below is a structured training approach tailored to your goals, featuring a strength-focused routine and a cardio protocol suitable for a fasted state.
Recommended Strength Program (Fasted State)
This program stimulates muscle tissue without excessive glycogen depletion, making it safer for a fasted environment. The focus is on compound movements with moderate volume.
Program Notes:
Recommended Cardio Protocol (Fasted State)
| Exercise | Sets | Reps | Primary Muscle Group | Purpose |
|---|---|---|---|---|
| Goblet Squat | 3 | 10–12 | Quads, Glutes, Core | Lower body strength & mobility |
| Dumbbell Walking Lunge | 3 | 10 per leg | Quads, Glutes | Unilateral stability & strength |
| Push-Ups (or Bench Press) | 3 | 8–12 | Chest, Triceps, Shoulders | Upper body pushing strength |
| Romanian Deadlift (Dumbbell) | 3 | 10–12 | Hamstrings, Glutes | Posterior chain development |
| Plank | 3 | 30–45 sec | Core (Abdominals) | Core stability |
Low-Intensity Steady State (LISS) is ideal for working out while pursuing weight-loss goals because it relies primarily on fat for fuel, sparing muscle glycogen (20).
| Activity | Duration | Intensity | Heart Rate Target |
|---|---|---|---|
| Brisk Walking / Incline Walk | 30–45 mins | Low-Moderate | Zone 2 (60-70% Max HR) |
| Cycling (Stationary or Road) | 30–45 mins | Low-Moderate | Zone 2 (60-70% Max HR) |
| Elliptical Trainer | 30 mins | Low-Moderate | Zone 2 (60-70% Max HR) |
Exercise Execution Instructions
Proper form is non-negotiable, especially when fasted, as fatigue can set in differently.
Goblet Squat
Dumbbell Walking Lunge
Push-Ups
Reasons why BetterMe is a safe bet: a wide range of calorie-blasting workouts, finger-licking recipes, 24/7 support, challenges that’ll keep you on your best game, and that just scratches the surface! Start using our app and watch the magic happen.
Romanian Deadlift (Dumbbell)
Plank
Yes, beginners can try working out while fasting, but caution and gradual progression are essential. If you are new to both fitness and fasting, diving into a 16:8 intermittent fasting morning workout immediately might be overwhelming.
When you are new to fasting, your body is not yet “fat-adapted.” Most bodies get used to having a steady supply of glucose. Suddenly removing that fuel source and adding exercise stress can lead to hypoglycemia (low blood sugar).
Symptoms include dizziness, shakiness, lightheadedness, nausea, and extreme weakness (21).
Strategy for Beginners:
It is crucial to avoid common pitfalls when starting. You can learn more about what not to do in our guide on intermittent fasting mistakes.
This is the most common question, and the answer requires nuance.
During the workout: Yes. As mentioned earlier, exercising in a fasted state increases the percentage of energy derived from fat oxidation during the session. Because insulin is low and glycogen is preserved (to an extent), the body mobilizes free fatty acids from adipose tissue (23).
Over 24 hours: Not necessarily. This is where the concept of total energy balance comes in. If you burn more fat during your workout but then compensate by eating more calories later in the day, or if your overall activity decreases because you are tired from the fasted session, your net fat loss may not change.
Research has shown that for fat loss, the total calorie deficit matters more than whether you trained, fed, or fasted (24).
Think of fasted training as a way to “teach” your body to be a better fat burner (metabolic efficiency), rather than a magic trick that bypasses the laws of thermodynamics.
Read more: 20-Hour Fasting Diet: Everything You Need to Know Before Attempting This Intermittent Fasting Plan
Building muscle (hypertrophy) while fasting is possible, but it is not the most optimal state for maximum growth.
Muscle growth requires 2 main things:
When you train fasted, you are in a catabolic (breakdown) state. To switch to an anabolic (building) state, you must break your fast post-workout with adequate nutrition (26).
The Key is Timing:
If you perform a 16:8 intermittent fasting morning workout, you must ensure your eating window provides enough total protein (approximately 1.6 grams per kg of body weight, or roughly 0.7 grams per lb of body weight) and sufficient calories to support recovery (27).
For those working out while fasting for 24 hours (OMAD or longer), muscle building becomes significantly harder. The window for getting the necessary nutrients is very small, and protein synthesis rates may be capped. If hypertrophy is your main goal, shorter fasts (like 16:8) are far superior to prolonged fasting protocols.
The fear of “burning muscle” is largely exaggerated, but it is a valid concern if you are not careful. Your body prizes muscle tissue and will generally try to protect it unless you are in a severe calorie deficit or completely sedentary.
Here are the research-informed strategies to preserve lean mass:
If you stop training, your body views that muscle as expensive tissue it doesn’t need to maintain.
If you find yourself plateauing or feeling weaker, you might be encountering workout problems related to under-fueling.
Fasting prioritizes burning glycogen (stored sugar) over body fat; some muscle protein is converted to glucose, but muscle tissue is generally preserved unless the fast is prolonged (several days) or body fat percentage is extremely low (31). Individuals with a history of hypoglycemia, pregnant women, those with eating disorders, and high-performance athletes requiring maximum glycogen availability for competition should avoid fasted cardio. Yes, it is okay to lift weights while fasting (32). Focusing on moderate reps and staying hydrated are key to safety and performance. However, some people find they don’t see the gains or performance improvements they aim for when lifting weights without adequate fuel. You should not break your fast with highly processed, sugary foods or a massive binge meal, as this can cause a rapid insulin spike and digestive distress (27). Aim for a balanced meal of easily digestible, nutrient-dense foods. Frequently Asked Questions
Does fasting burn fat or muscle first?
Who should avoid fasted cardio?
Is it okay to lift weights while fasting?
What should I not do after fasting?
Working out while fasting can be a powerful strategy for those looking to optimize metabolic flexibility and simplify their fitness routine. It is not a magic pill, but rather a lever you can pull to enhance fat oxidation and improve insulin sensitivity.
By understanding the distinction between fasted and fed states, and by choosing the right exercise intensity–like the strength and cardio plans outlined above–you can reap the benefits of exercise while fasting without sacrificing muscle or performance.
Remember, the best fitness protocol is the one you can sustain. Whether you are doing a 16:8 intermittent fasting morning workout or occasionally experimenting with working out while fasting 24 hours, listen to your body.
The most important thing is consistency, so if it works better for you to fuel up before exercise, then do that.
Start slow, prioritize protein in your eating window, and treat your training with the respect it deserves. Your body is an adaptable machine; give it the right inputs, and it will give you the results you want.
This article is intended for general informational purposes only and does not serve to address individual circumstances. It is not a substitute for professional advice or help and should not be relied on for making any kind of decision-making. Any action taken as a direct or indirect result of the information in this article is entirely at your own risk and is your sole responsibility.
BetterMe, its content staff, and its medical advisors accept no responsibility for inaccuracies, errors, misstatements, inconsistencies, or omissions and specifically disclaim any liability, loss or risk, personal, professional or otherwise, which may be incurred as a consequence, directly or indirectly, of the use and/or application of any content.
You should always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or your specific situation. Never disregard professional medical advice or delay seeking it because of BetterMe content. If you suspect or think you may have a medical emergency, call your doctor.