Fasted Strength Training: Good or Bad for Your Gains?

Many people enjoy lifting weights on an empty stomach, while others shudder at the very idea. Some only have time to hit the gym early in the morning. Others just prefer fasted strength training because they don’t like the feeling of exercising after a meal or with a full stomach.

In this article, you’ll learn what happens when you lift weights in the fasted state, if strength training on an empty stomach is a good idea, if it’s safe to do so, and whether it hinders muscle gain.

Fasted Strength Training: Yay or Nay?

When it comes to fasted strength training, you often find lifters firmly in two different camps: those who swear by it and those who wouldn’t dream of lifting weights before breakfast.

The first group claims various benefits from lifting weights before eating.

  • According to popular belief, you burn more fat when you work out fasted than if you exercise in the fed state.
  • When you haven’t eaten for a long time, your growth hormone levels go through the roof.1 Many people believe that fasted strength training takes advantage of that growth hormone peak for building muscle and greater fat loss.
  • Lifting weights on a full stomach can be uncomfortable. Throwing up during a squatting session is not optimal for performance or muscle growth.

Others avoid lifting weights on an empty stomach at all costs. 

  • They fear that fasted weight training increases muscle breakdown and makes you lose lean muscle mass.
  • Your muscles require amino acids to grow. Without protein, they lack the building blocks they need to add new muscle tissue.
  • Feeling hungry during a workout is a distraction and takes your focus away from the lifting.
  • If you haven’t eaten, your body doesn’t have the energy levels to get through a high-intensity training session, right?

Both sides make sensible arguments, and the points have merit, but some are only relevant when taken out of context. Let’s break them down.

Fasted gym sessions do indeed increase fat oxidation.2 However, there is little evidence that exercising on an empty stomach leads to more significant fat loss. Not even if we’re talking about cardio before breakfast.3 Fat loss is more about calories in vs. calories out than working out at a particular time of day.

As for growth hormone, it does little for adult muscle growth.4 Despite its name, growth hormone is a starvation hormone that helps your body use fat and carbs as fuel. It doesn’t help you gain muscle, at least not if we’re talking about physiological levels, amounts you can achieve through training or fasting.

After lifting weights, muscle protein breakdown does increase. However, so does muscle protein synthesis, the process of building new muscle. Muscle protein synthesis increases more than muscle protein breakdown, even if you lift without eating.5 Strength training doesn’t lead to muscle growth until you eat, but it never increases muscle loss.

And if you eat after a fasted strength training workout, you flip the switch and start adding new muscle tissue at a much higher rate than you break down muscle. 

fasted strength training build muscle

In other words, you don’t have to eat before a workout to promote muscle growth. Simply give your muscles the building materials they need post-workout instead. In most studies showing how strength training and protein work together to add muscle tissue, the participants don’t eat anything before lifting.6 7

As for the energy to lift, it likely depends on your personal preferences. A small study showed that skipping breakfast decreased exercise performance in the gym.8 However, the participants were all regular breakfast eaters. They couldn’t do as many reps as usual when they, for once, didn’t eat breakfast, but that could simply be the result of not being used to lifting on an empty stomach. The researchers also speculated that it could have been a placebo effect. 

A recent review found that you benefit from eating carbohydrates before working out if you haven’t eaten anything for more than eight hours, like after an overnight fast.9 You don’t have to load up on massive amounts of carbs, but something is better than nothing for most people.

So far, everything points to the same thing: it doesn’t really matter if you train fasted or after eating. It certainly won’t make or break your results.

That leaves two things: the potential discomfort of training after eating or feeling hungry if you don’t.

If you’re uncomfortable or sick to your stomach when you lift weights after eating, and you feel you lack the energy to go all-out in the gym, you could try eating a smaller meal with easily digestible carbs like some cream of rice or a banana. A few carbs can make a big difference, and you don’t have to eat any protein before you work out as long as you do it afterward. If that doesn’t work, you could sip on a sports drink during your training session for energy. But if you have the energy to work out and prefer to do so fasted, go right ahead. It’s mostly a matter of personal preference.

Feeling hungry can undoubtedly be distracting, but not everyone reacts that way. Some feel that being a little hungry in the gym allows them to hit the weights more aggressively and with complete focus. If you cannot focus in the gym because you’re only thinking about food, that’s a problem. Consider at least a small pre-workout snack to tide you over. Feeling ravenous is probably a distraction for anyone but being hungry for a couple of hours is not dangerous or a sign that something is wrong.

I suggest you listen to your body and do what it tells you. Some people feel their energy is higher and perform better before eating. If that describes you and you notice that you perform just as well or better in the gym without eating, that’s what matters. Gym sessions lasting hours might not be optimal, though, as you’d deplete your glycogen stores which are your primary fuel source during intense exercise. And most people experience better performance after eating something.

If your schedule makes early morning workouts before breakfast the only option, and you find you don’t enjoy them, give it a few weeks. It can take some time for your body to get used to fasted strength training.

Now, let’s dive deeper into what happens when you lift weights on an empty stomach. Does it build muscle, and is fasted high-intensity lifting safe? And what about cardio? Is it more effective for fat-burning purposes after long periods of fasting?

Can You Build Muscle with Fasted Strength Training?

One of the main reasons many lifters avoid strength training on an empty stomach is because they think it might interfere with muscle growth.

As I said earlier, in most studies on resistance exercise and protein, the participants engage in fasted strength training. It’s much easier to measure the effects of protein intake following a workout if you don’t have amino acids and nutrients from a pre-exercise meal circulating.

Without exception, research shows that fasted strength training boosts muscle protein synthesis (MPS). MPS can’t become greater than muscle breakdown until you eat, though. You don’t have to sit down to a complete breakfast immediately after an a.m. workout, but you need some kind of post-workout meal containing protein, be it a protein shake or a full meal, before you can start gaining muscle. Once you give your muscles some protein, you flip the switch to boost MPS even if you trained completely fasted.

The bottom line: in the fasted state, muscle breakdown is always more significant than muscle protein synthesis. Once you eat, you start building more muscle than you break down. If you prefer lifting weights without eating, you don’t have to worry about losing muscle as long as you eat afterward. Just don’t train fasted and continue fasting for many hours after your workout.

As for long-term muscle growth, there aren’t many studies comparing regular weight training in the fed- vs. fasted state. However, a few studies on Muslim bodybuilders did not find any significant difference in body composition depending on whether they trained fasted.10 11

While there aren’t many long-term studies examining strength training on an empty stomach, many real-world examples demonstrate that athletes and bodybuilders can build tremendous physiques with fasted strength training. While you probably won’t see a Mr. Olympia contender lifting weights on an empty stomach, it should not prevent you from reaching your fitness goals.

Fasted Strength Training: From Theory to Practice

So, you’ve decided to give lifting weights on an empty stomach a go. Maybe it’s the option that best fits your schedule, or you simply feel uncomfortable lifting after eating.

Here are a few things you should consider.

  • Eat a complete meal in the afternoon or evening before your fasted workouts. Giving your body the chance to store the energy as muscle glycogen will help you perform your best in the gym during a fasted workout.
  • When you work out fasted, make sure you eat or drink some type of protein after your training session. You don’t have to have a protein shake ready once you finish your last set but try to consume 20–40 grams of protein within a reasonable time frame. Training in the morning on an empty stomach and then not eating until dinner is likely a bad idea. There are no studies on such a scenario, but I wouldn’t be surprised if it is awful for your gains.
  • If your training sessions are long, maybe 90 minutes or more, consider a small pre-workout snack consisting primarily of carbohydrates before hitting the gym. It’ll stabilize your blood glucose levels and could keep you going for longer without making you feel heavy or bloated.
  • Drink plenty of water if you train in the morning before breakfast. Not eating before lifting weights is one thing, but not drinking is another. You’ll be partially dehydrated after a night’s sleep, and your muscles don’t like high-intensity exercise in a dehydrated state. If you work out fasted in the evening, you have probably been drinking water during the day.

Workout Splits for Fasted Strength Training

You don’t have to follow a particular training program if you prefer resistance exercise on an empty stomach. You can do anything without eating beforehand, including lifting weights.

That being said, your training sessions shouldn’t be overly lengthy and draining for the best results and to maintain your energy levels.

You’ll find several training programs perfect for fasted strength training in your StrengthLog app.

StrengthLog’s Upper/Lower Body Split Program is one of the best options for general strength training. The training volume is high enough to give excellent results but not too high for a fasted workout.

Upper Lower Body Split Program fasted strength training

Bodybuilding for Beginners is our training split for, you guessed it, beginners to the world of bodybuilding. Full-body workouts three times per week, focusing on the basics, might be the best introduction to building muscle, and that’s what you get with Bodybuilding for Beginners.

Bodybuilding Blitz is a premium 5-day workout split for intermediate to advanced bodybuilders looking to build muscle without spending hours in the gym. Training only 30–40 minutes per workout, you get the best possible results per invested minute.

Read more:

>> The 10 Best Bodybuilding Splits: a Complete Guide

You can find these three workout splits and many more for all experience levels in StrengthLog. It is free to download, entirely without ads, and you can check it out by clicking one of the buttons below:

Download StrengthLog Workout Log on App Store fasted strength training
Download StrengthLog Workout Log on Google Play Store fasted strength training

Is It Safe to Lift Weights on an Empty Stomach?

Absolutely, assuming you’re healthy. You can do anything without eating, including physical activity, high-intensity workouts in the gym, or any other types of exercise. It would make zero evolutionary sense if we had to eat before we gathered food or hunted.

If you have a medical condition or take medicines that affect your blood sugar, or if you’re pregnant, you should talk to your doctor first. For example, if you have type 1 diabetes, fasted strength training can be a viable option, but it does produce a different blood glucose response compared to working out after eating.12 Because everyone is different, it’s best to get medical advice first.

However, if you’re healthy, nothing suggests that it is bad for you to work out fasted. You might not enjoy it, but it’s not bad for you. Then again, you might even find that you prefer it. In addition, exercise in the fasted state is associated with potential benefits like improved insulin sensitivity.13

What and When to Eat Before Lifting Weights?

If you don’t want to train fasted, you have many options depending on when you plan to work out. If you’re heading to the gym in three or more hours, you have time to eat, digest, and take advantage of a full meal, but if you’re off in 30 minutes, you don’t want to load up on something that’s going to lie in your stomach during your training session.

Three to Four Hours Before Training

If you can plan your training and eating to allow for 3–4 hours between your last meal and your workout, you have the luxury of having a regular lunch or dinner. Getting up hours earlier to eat a large breakfast before an early morning workout is probably not worth the effort, so save this strategy for when you train later in the day. A quality protein source like meat, fish, eggs, lentils, or beans, along with a long-lasting carb source like rice, pasta, potatoes, or oatmeal, gives you both the protein you need to build muscle and the energy to fuel your workout.

One to Two Hours Before Training

If your workout starts 1–2 hours following your pre-exercise meal, you might not perform your best if you load up on a massive dinner-style meal. It can make you feel sluggish rather than filled with energy. A protein-rich smoothie with some protein powder, oats, and berries is a better idea, as is some Greek yogurt with rolled oats and a banana.

Less Than One Hour Before Training

If you haven’t eaten all day or train early in the morning after getting out of bed and don’t have time to whip up anything resembling a proper meal, a small snack like a piece of fruit and a protein shake will get you going without making you feel uncomfortable.

During Training

No time or opportunity to eat anything before working out? Liquid intra-workout nutrition might be the answer. Mix some dextrose, maltodextrin, or a commercial sports-drink powder in water, and add some EAAs (Essential Amino Acids). Sip on it during your workout, and you have an energy source and building blocks for your muscles in a convenient package that takes no time to prepare. Make sure you’re using an EAA supplement, not a BCAA supplement. A BCAA supplement contains only the three branched-chain amino acids, which is not enough.14 15

Do You Burn More Fat If You Train on an Empty Stomach?

What about cardio, you might ask. Many people work out fasted to burn more body fat. Is there anything to fasted exercise for weight loss?

There is no doubt that you “burn” more fat during fasted aerobic exercise compared to after a meal.16 There are significant differences in your hormonal status in the morning after a night of fasting compared to late in the day after several meals. Adrenaline and growth hormone increase fat oxidation, and your insulin levels are way down.

Doing your cardio fasted while your insulin and blood glucose levels are low optimizes fat oxidation during your workout and release fatty acids from your body fat into your blood, where they are used as energy.

The bad news is that the increased fat burning while you’re exercising in the fasted state does not automatically mean that your body fat stores decrease over time. You see, your body is very good at balancing things. If you burn more fat during a particular time of the day, you burn less or store more at some other point.

The most important thing for fat loss is your caloric intake vs. how many calories you burn. Over time, not during an hour or two. You need to create a caloric deficit to lose body fat. The timing of your cardio does not seem to matter much.

According to research, fasted cardio does not lead to meaningful body composition changes or reduce fat mass more than performing it after eating.3 17 18 Older studies even suggest that fasted cardio might not be a good idea for strength athletes and others looking for strength gains and building lean body mass because of muscle breakdown. However, that’s probably not a cause of concern unless you starve yourself.

Anecdotal evidence suggests that fasted cardio might be helpful to lose the last body fat when you’re already lean and trying to get shredded. However, there is no scientific research to back it up. It could be worth trying, though, as there are no downsides to doing so.

Once again, it comes down to personal preference. If you enjoy fasted cardio, go right ahead. It can be a great way to get the day started. Don’t expect to burn fat more effectively, though. If you despise the thought of any type of exercise on an empty stomach, or if it doesn’t fit your schedule: don’t worry. You can safely do your cardio after breakfast, during the late afternoon, or at the end of the day, before or after eating. Any time is the best time.

Final Words

Fasted strength training (and cardio) is both effective and safe. Lifting weights on an empty stomach is not more effective than doing so after eating one or more meals. But if you, for whatever reason, prefer fasted resistance training, there is no evidence that it will prevent you from reaching your fitness goals. As long as the quality of your workouts isn’t negatively affected, you’re good to go.

If you can’t or don’t like to train fasted, don’t worry. You’re not missing out on life-changing health benefits or dramatic positive effects in muscle gains or weight management.

Personal preference is the keyword when deciding whether fasted strength training is for you. And that’s a good thing. Lifting weights is the best way to gain strength, build muscle, and improve your body composition, but when you train matters little.

References

  1. The Journal of Clinical Endocrinology & Metabolism, Volume 74, Issue 4, 1 April 1992. Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men.
  2. Int J Exerc Sci. 2018; 11(2): 827–833. Effects of Prior Fasting on Fat Oxidation during Resistance Exercise.
  3. Journal of the International Society of Sports Nutrition volume 11, Article number: 54 (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise.
  4. Br J Sports Med. 2003 Apr; 37(2): 100–105. Claims for the anabolic effects of growth hormone: a case of the Emperor’s new clothes?
  5. The Journal of Nutrition, Volume 136, Issue 2, February 2006, Pages 525S–528S. Skeletal Muscle Protein Metabolism and Resistance Exercise.
  6. Medicine & Science in Sports & Exercise: December 2004 – Volume 36 – Issue 12 – p 2073-2081. Ingestion of Casein and Whey Proteins Result in Muscle Anabolism after Resistance Exercise.
  7. Am J Physiol. 1999 Apr;276(4):E628-34. Postexercise net protein synthesis in human muscle from orally administered amino acids.
  8. Journal of Strength and Conditioning Research: July 2019 – Volume 33 – Issue 7 – p 1766-1772. Breakfast Omission Reduces Subsequent Resistance Exercise Performance.
  9. Sports Medicine (2022). The Ergogenic Effects of Acute Carbohydrate Feeding on Resistance Exercise Performance: A Systematic Review and Meta-analysis.
  10. Journal of the International Society of Sports Nutrition volume 10, Article number: 23 (2013). Effect of fed- versus fasted state resistance training during Ramadan on body composition and selected metabolic parameters in bodybuilders.
  11. Int J Sport Nutr Exerc Metab. 2012 Aug;22(4):267-75. Effect of resistance training during Ramadan on body composition and markers of renal function, metabolism, inflammation, and immunity in recreational bodybuilders.
  12. The Journal of Clinical Endocrinology & Metabolism, Volume 104, Issue 11, November 2019, Pages 5217–5224. Morning (Fasting) vs Afternoon Resistance Exercise in Individuals With Type 1 Diabetes: A Randomized Crossover Study.
  13. Sports Medicine volume 47, pages 415–428 (2017). Impact of Endurance Exercise Training in the Fasted State on Muscle Biochemistry and Metabolism in Healthy Subjects: Can These Effects be of Particular Clinical Benefit to Type 2 Diabetes Mellitus and Insulin-Resistant Patients?
  14. Journal of the International Society of Sports Nutrition, Volume 14, 2017 – Issue 1. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?
  15. Int J Sport Nutr Exerc Metab. 2021 May 1;31(3):292-301. Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review.
  16. Br J Nutr. 2016 Oct;116(7):1153-1164. Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis.
  17. Strength and Conditioning Journal: February 2011 – Volume 33 – Issue 1 – p 23-25. Does Cardio After an Overnight Fast Maximize Fat Loss?
  18. J. Funct. Morphol. Kinesiol. 2017, 2(4), 43. Effect of Overnight Fasted Exercise on Weight Loss and Body Composition: A Systematic Review and Meta-Analysis.
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Andreas Abelsson

Andreas has over 30 years of training experience and is a highly appreciated writer and educator on exercise, fitness, and nutrition. Few people stay more up to date and have a better grasp of the field of exercise science than Andreas.