Fasted Weight Training: Is It Killing Your Muscle Gains?

A lot of people do cardio first thing in the morning on an empty stomach before eating breakfast, hoping that this will increase fat loss. For sure, fasted cardio can help with fat loss, but the latest research says it’s probably no better than fed cardio. We covered that topic in the last blog post here.

fasted weight trainingWhat’s interesting is that a lot of people still believe that fasted cardio in the morning is good, but at the same time, the majority of trainees have always believed that fasted weight training is bad.

The main concern is that lifting on an empty stomach could zap your energy, strength, and performance. Another worry is whether you won’t build as much muscle if you lift with no protein in your system.

One of the reasons this subject of fasted weight training has come up more often in recent years is because fasting diets became a popular trend. Some diet gurus who promote fasting have even made the controversial claim that lifting fasted builds more muscle (which is patently false).

Another reason fasted weight training is discussed so often is because so many people train early in the morning and find it uncomfortable with a meal sloshing around in their stomach. If they have to get to work, they don’t have time to wait an hour for breakfast to digest. So to avoid feeling nauseous, they lift fasted, and eat afterward.

But a lot of these people aren’t sure if this practice is good or bad for their gains. They wonder if they’d be better off forcing down that pre-workout breakfast or training later in the day after some meals are in their system.

In addition, a widely publicized study recently showed that lifting in the morning after skipping breakfast decreases performance. That’s had people scrutinizing fasted training more closely as well.

There are reasons to believe fasted lifting is not optimal, especially if you do it later in the day after after a prolonged fast (as it might be on a time-restricted feeding diet). If you look at all the research, however, lifting before breakfast might not be a problem, as long as you can maintain your performance. This is especially true if you ate a big dinner the night before, as that essentially becomes your pre-workout meal.

What Does The Research Say?

There have been several studies on fasted lifting. One looked at the effects of weight training on Muslims who were fasting during Ramadan. This is the holy month where they only eat solid food before sunrise and after sunset. A lot of athletes who observe Ramadan will keep training during these fasting periods.

The researchers thought weight training could be done safely during Ramadan while fasting, but also suspected there could be a negative effect on body composition. At the end of the four week study, contrary to their hypothesis, there was no difference in body composition either way. They said this was likely because these bodybuilders were able to keep up their lifting volume and performance. This was only a month-long study, but it provides some evidence that lifting fasted doesn’t always produce negative outcomes.

But whether fasting affects your workout performance is important to consider, because in other studies, athletes who kept training or practicing their sport during Ramadan did suffer a drop in speed, endurance and energy. One study with fighter pilots as subjects also found a decrease in muscular performance during Ramadan fasting.

The newest study was published in the Journal of Strength and Conditioning Research. It was named, “Breakfast omission reduces subsequent resistance exercise performance.” As the title implied, performance decreased in the group that didn’t eat breakfast. Specifically, the repetitions were 15% lower in the squat and 6% lower in the bench press.

Is that a nail in the coffin for fasted lifting? Not necessarily, but it does tell us that pre-workout food intake may be more important when you’re training with high volume and intensity. In this study, the subjects were doing multiple sets with the reps in the hypertrophy range. They were also training to failure. If you’re doing a shorter, less intense, or lower rep workout, then a drop in performance when training fasted is less of a concern.

One more detail, that’s often overlooked, is that the subjects in this study were habitual breakfast eaters. If you’re used to eating breakfast before a morning workout, and then you start skipping breakfast, it wouldn’t be surprising if your performance took a dive. But people who are habituated to not eating breakfast may not have the same problem.

Also, if you’re used to training later in the day after eating and you switch to lifting fasted in the morning, it may feel rough at first, but your body can adapt. You might want to give it a little time before you decide for or against it.

Important Considerations If You Lift Fasted

The research is still limited in this area, but there is evidence that fasted weight training could compromise lifting performance for some people, especially during high-volume workouts.

It also looks like both individual preference and response may vary. Some people say they like training fasted and their performance is fine. Others hate training on empty and find their performance suffers.

Which way you choose to do it might come down to personal preference or convenience as much as anything. If you’re thinking about lifting fasted, there are a few questions you should ask yourself.

1. Is fasted weight training hurting your training energy or reducing your performance?

Do you want to know if it’s a good or bad idea for you to lift fasted? A simple way to answer is to try it both ways, compare how you feel training fed versus fasted, and see if training fasted is causing a drop in performance. If so, it might not be the best idea for you. Remember, if your strength or performance drop, then it’s safe to assume, so will your muscle gains.

2. Are you eating quality food and hitting your targets for calories, protein, carbs and fat by the end of every day?

There was a point years ago when the biggest trend in bodybuilding nutrition was nutrient timing. Eating before training was recommended, and eating immediately after lifting was considered vitally important. Most people back then believed that if you missed this post-workout “window of opportunity,” you would compromise the muscle growth potential from the workout.

Today, research has shown that nutrient timing is still important in many ways, but it’s a secondary factor. Some top coaches believe it counts for just 10% of your results. When you eat your meals is not what makes or breaks you. In muscle-building nutrition, the most important priority is hitting your calorie and macro targets for the day, especially protein.  So if you don’t eat before you lift, but you’re eating quality food and consistently nailing your daily macro goals, you’ll still make gains.

3. Are you getting a post-workout meal quickly after training?

If you eat a meal with protein before your weight training workout, the amino acids will still be hitting your system during and right after your workout. When you eat a pre-workout meal, the urgency of the post-workout meal is not as high. If your post-workout meal was an hour or two after training, that would be fine.

However, if you decide to weight train fasted, that changes things. Then the post-workout meal does become more urgent.  If you lifted fasted, and you want to optimize your muscle growth response to the training, then you should eat your post-workout meal immediately after lifting. It should be easy to digest, include protein, and be a substantial size too.

Current Nutrient Timing Guidelines For Optimal Muscle Gains

Anyone with serious muscle-building goals might want to look at their meal timing in terms of what’s optimal, and aim to get 100% of the possible growth potential rather than settle for 90%.

What is optimal for muscle growth?

Two nutrition and training researchers – Alan Aragon and Brad Schoenfeld – analyzed 85 different studies to develop new best practices for nutrient timing, including the timing of nutrient intake around workouts.

The guidelines were published in the Journal of the International Society of Sports Nutrition, and when it came to the protein prescription, there were two points:

1. For optimal results, eat 0.4 to .5 grams of high-quality protein per kilogram of lean body mass both before and after (resistance) training.

2. For optimal results, the pre- and post-workout meals should not be separated by more than 4 hours.

Using this guideline, someone with 70 kilos of LBM would have between 28 and 35 grams of protein in both the pre- and post-exercise meals. If you eat more protein than this (staying within your calorie budget), there’s no downside. But if you skip either protein feeding or fall short, you might not optimize the anabolic response from your workout.

Make a note that this scientific guideline for nutrient timing includes eating protein both before and after lifting. That means not fasted – at least not totally fasted. At the minimum, this suggests that you should eat protein before training as well as after, if you want to optimize muscle growth.

In both the pre- and post-workout meal, the protein is most critical part. How important the carbs are before and after for muscle growth in strength-trained athletes is still being studied.

Most physique athletes eat carbs before training because they hope to increase energy and many lifters see a correlation between their training energy and the carb content of their pre-workout meal. They also eat carbs in the post-workout meal for recovery. But precise carb intakes for replenishing glycogen are a bigger priority for endurance athletes than for lifters and bodybuilders.

Fasted Weight Training: The Bottom Line

Personally, I think these latest evidence-based pre- and post-workout nutrient timing guidelines are sensible. They also match what most successful bodybuilders have been doing for years – they “bracket” their training with a protein-containing meal on each side.

If maximum muscle growth is your goal, then least having a pre-workout protein shake or a light protein snack looks like a good move compared to lifting totally fasted. For long (an hour+), intense, high-volume workouts, including more carbs is also likely optimal for performance.

As I mentioned earlier, the challenge for many people is they lift early in the morning. If they eat a full breakfast beforehand, they feel like they’re going to throw up. Some say they can’t lift with anything at all in their stomach or they feel sick. If you’re in this group, should you be worried about sub-optimal gains? Probably not much. You could switch your training to afternoon or evening when you can eat, allow time for digestion, then lift, and see if your results improve or if there’s no difference.

But based on science and personal experience, here’s what we can predict will happen if you lift fasted: It will either make no difference either way, or only cause a slight drop in performance. The only way to know is to try both ways and find out for yourself.

If you’re doing it fasted, simply remember these important points:  make sure your workout performance isn’t suffering, have a meal high in protein right after training, eat protein beforehand if possible (30 grams of whey in water is pretty easy on the stomach) and make sure you hit your macro goals by the end of every day. If you cover those bases, you’ll probably do fine even when lifting on empty.

On the other hand, don’t expect to get better results from fasted weight training. If a diet guru claims that lifting fasted increases muscle growth, or is better than training fed, you can ignore it, because the research isn’t there to support it.

-Tom Venuto,
Founder, Burn the Fat Inner Circle
Author, Burn the Fat, Feed the Muscle

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Scientific references:

Aragon A., Schoenfeld B. Nutrient Timing Revisited – is there a post-exercise anabolic window? Journal of the International Society of Sports Nutrition, 10:5, 2013.

Faye J, et al. Effects of Ramadan fast on weight, performance and glycemia during training for resistance. Dakar Médical, 2005; 50 (3): 146-151.

Frawley K et al. Effects of prior fasting on fat oxidation during resistance exercise. Int J Exerc Sci, 11:2, 827-833, 2019.

Nashrudin, M, et al. Breakfast omission reduces subsequent resistance exercise performance. Journal of Strength And Conditioning Research, 33:7, 1766-1772, 2019.

Trabelsi, K et al. Effect of fed- versus fasted state resistance training during Ramadan on body composition and selected metabolic parameters in bodybuilders. Journal of the International Society of Sports Nutrition, 10:23, 2013

Zerguini Y, et al. Impact of Ramadan on physical performance in professional soccer players. British Journal of Sports Medicine, Jun, 2007; 41 (6): 398-400.

Related: Fasted Cardio Revisited

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