It’s seemingly easy to go the entire night without eating food; it’s not like you wake up mid-sleep to grab a snack. But when you translate that into the waking hours, fasting becomes a bit more challenging.

Temptation always seems to be around the corner whispering in your ear to eat that burrito or heat up that slice of pizza.

Fasting is difficult—there’s no two ways around it.

And if you’re the type of person that likes to hit the gym first thing in the A.M., that fast probably just became even less tempting to do.

What is Fasting?

Fasting is the practice of going extended periods of time without food. It can range anywhere from 12 hours to beyond 24 hours depending on the type of fast you’re doing and what you’re trying to achieve.

Of course, with fasting, the longer you do it, the more physiological benefits you’ll see.

For example, a fast of 48 hours or more will fully deplete glycogen stores and put you into ketosis, whereby your body converts fat to ketones that supply the brain with fuel; unlike a lot of other compound, ketones can easily permeate the blood-brain barrier to provide energy during prolonged fasting [1].

It will also stimulate autophagy, or the process of culling old, worn-out cells to make room for new, healthy ones [2].

You can read more about the benefits of fasting in our "Intermittent Fasting and Strength Training" article.

Training (Cardio or Lifting Weights) in a Fasted State

A lot of people swear by doing cardio in a fasted state.

You’ll see people hop straight out of bed and hit the treadmill, spin bike, or any other machine that ramps up your heart rate without having a bite of food.

And while it’s okay to do just about anything in a fasted state, including lifting weights, you just have to be aware that the quality of your workout may not be comparable to that of one in a fed state.

How about fat loss in a fasted state?

If you’re looking for fat loss, on the other hand, training in a fed versus a fasted state makes minimal different long-term even though studies suggest that fasted weight training does increase fat burning [3].

It gives you just a snippet of the entire picture, but if you’re going to say fasted training results in increased fat loss, you have to look at the entire picture long-term.

From a body composition standpoint, there isn’t much research, or at least minimal conclusive research, to support fasted training over fed.

Two studies published in the Journal of the International Society of Sports Nutrition—one using male bodybuilders training in both a fasted and fed state and one with aerobically trained women—found that changes to body composition remained either unchanged or very similar between the fasted and non-fasted groups [4, 5].

Can You Build Muscle Weight Training in a Fasted State?

Is it better to stack pancakes or just head straight to stacking plates?

Contrary to what most people think, it is possible to build muscle while training in a fasted state.

If you’re looking to put on strength or muscle mass, it may be more difficult to achieve without adequate energy.

And this is especially true if you’re involved in intense strength-training workouts; they can be extremely and unnecessarily challenging to do in a fasted state.

However, there is one thing on your side...

Muscle growth isn’t entirely dependent on whether or not you have food in your system while you’re training

The process of building, repairing, and breaking down muscle tissue isn’t that fast and it will take more than the time you’re putting in during a training session to do so.

Assuming you have an adequate amino acid pool to draw from, your body isn’t going to pull from existing muscle tissue to support new muscle synthesis.

Establishing the fact that it is possible to build muscle in a fasted state, if you’re looking to gain as much strength and muscle mass in the shortest time possible, it’s probably not the most ideal situation.

This is because research demonstrates that fasted training increases the rate of muscle protein breakdown more so than in a fed state [6].

Building muscle ultimately boils down to muscle protein synthesis exceeding muscle protein breakdown long-term. 

Doing anything that throws off the balance and tips the scale more in favor of catabolism and away from anabolism (like fasted training) is only going to make it more difficult to build muscle as quickly and efficiently as possible.

Important Points to Consider about Fasted Weight Training

Training in a fasted state can have an overall positive effect, but the results you’re looking to achieve may be compromised and dependent on:

  • The type of training you’re doing
  • How long you’ve been fasting
  • What you’ve eaten the day before

And even with these three things in mind, there is still a degree of variability between people.

#1: The type of training you’re doing

Fasted training is generally the talk of the town when it comes to cardio because theories have it that once you’ve been fasting for an extended period of time, you’ve burned through stored glycogen and it becomes easier for your body to tap into fat stores for energy.

However, the merit behind this one is questionable because it takes longer than 12 hours without food to burn through 2000 calories worth of stored glycogen.

But when it comes to strength training in a fasted state, studies suggest that you may not be doing yourself any favors.

One study looked at the effects of breakfast omission on strength training [7]. Sixteen trained men were put into two groups: the first consuming a meal containing 1.5g carbohydrates/kg of body weight, and the second consuming only water.

Two hours later, participants performed 4 sets of back squat and bench press at 90% of their 10RM. Results showed that the group who consumed water only performed fewer repetitions for both back squat (15% less) and bench press (6% less).

Researchers concluded that omitting a pre-exercise meal may impair resistance exercise performance in people that usually consume food prior to training.

#2: How long you’ve been fasting

Resistance training first thing in the morning (after a 12 hour fast, for example) isn’t inherently problematic for everyone because if you’ve eaten a substantial meal the night before, your body likely still has glucose circulating and has retained its glycogen stores.

However, where problems may arise is if you’re leaving fasted training to later in the day and you’ve now been fasting for 16-20 hours plus.

At that point, your body has likely used up the circulating glucose and is now starting to deplete glycogen stores. If there isn’t a huge pool of energy to grab from for heavy lifts, both your performance and your strength may take a hit.

#3: What you ate the day before

The same goes for what you’ve eaten. If you’ve been following a low-carb style of eating and you haven’t consumed a hefty amount of carbs to max out glycogen stores, chances are your lifting capabilities are going to suffer.

You don’t have that immediate pool of energy available for your muscles to tap into, so you’re likely going to experience fatigue quicker than if your glycogen stores are topped up.

Final Word on Fasted Weight Training Benefits

These are all points that you need to consider before picking up a set of weights.

If fasted resistance training is going to do more harm to your body and compromise your goals, then it’s not worth it.

And while you may not lose muscle doing resistance training in a fasted state, there’s little evidence to suggest that you’ll gain any. 

Burn Lab Pro contains ingredients such as HMB to further ensure that you won't lose any hard-earned muscle mass while on a calorie-deficit or fasted training program.

References

  1. H White, B Venkatesh. Clinical review: ketones and brain injury. Crit Care. 2011; 15(2): 219.
  2. M Bagherniya, AE Butler, GE Barreto, A Sahebkar. The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Res Rev. 2018; 47: 183-197.
  3. AA Aragon, BJ Schoenfeld. Nutrient timing revisited: is there a post-exercise anabolic window? J Int Soc Sports Nutr. 2013; 10(1): 5.
  4. K Trabelsi, SE Stannard, Z Ghlissi, et al. Effect of fed- versus fasted state resistance training during Ramadan on body composition and selected metabolic parameters in bodybuilders. J Int Soc Sports Nutr. 2013; 10(1): 23.
  5. BJ Schoenfeld, AA Aragon, CD Wilborn, JW Krieger, GT Sonmez. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr. 2014; 11(1): 54.
  6. HT Pitkanen, T Nykanen, J Knuutinen, et al. Free amino acid pool and muscle protein balance after resistance exercise. Med Sci Sports Exerc. 2003; 35(5): 784-792.
  7. MN Bin Naharudin, A Yusof, H Shaw, M Stockton, DJ Clayton, LJ James. Breakfast Omission Reduces Subsequent Resistance Exercise Performance. J Strength Cond Res. 2019; 33(7): 1766-1772.