For some people, the thought of training in a fasted state makes them cringe, while for others, training fasted is their norm.

You can't argue that getting out of bed before the sun rises to get in a run, bike, or even a lift can make you feel like a million bucks after the fact, but when the temptation to press snooze is there, it's hard to resist.

But what if we told you that tweaking the time you eat your breakfast can give you a significant boost in the gym and help you reach your health and fitness goals?

Fasted workouts are a (sometimes) simple way to give your performance that boost you've always been looking for, and combined with things like HMB and BCAAs, you can max out your performance.

Why Fasted Training?

Fasted training is exactly like it sounds—training in a state where food has not been consumed for an extended period, usually overnight.

In order words, you don't eat breakfast before you hit the gym to get your body to switch fuel-burning gears.

Fasted training goes both ways. Some people love it and agree that it's highly beneficial, while others think it's incredibly detrimental to athletic performance.

Depending on the type of exercise you're doing, fasting can be beneficial.

Here's why:

1. It Increases Lipolysis

Without sufficient glucose supply, rates of adipose tissue lipolysis and peripheral fat oxidation increase.

This is due to higher plasma stress hormone concentrations (adrenaline and cortisol) in combination with lower circulating insulin levels 1.

These stress hormones interact with adipose tissue and trigger a cascade that stimulates lipolysis to increase circulating levels of free fatty acids.

Not just this, but training in a fasted state appears to upregulate genes involved in fatty acid transport and beta-oxidation in muscle fibers 2, resulting in enhanced skeletal muscle fat oxidation, even during periods of rest after training has halted.

Consuming food before training increases insulin levels and has been shown to attenuate certain metabolic responses to training, namely lipolysis enzymes, fatty acid transport, and fat oxidation.

2. Improves Insulin and Glucose Control

Before we get to this point, we need to cover a quick recap of how your body digests food.

When you consume food, it's broken down into its core constituents—glucose, amino acids, or fatty acids—that are then absorbed and utilized by the body, but before that can happen, it needs certain compounds.

When you eat anything with a carb count linked to it, your body responds by secreting insulin to enable glucose to enter cells; insulin essentially acts like a key that lets glucose enter.

However, when your cells don't respond to insulin, glucose cannot be taken up from the blood, and blood sugar remains high.

As a result, the pancreas secretes more insulin to help move glucose into cells, and now you're left with high insulin and high blood glucose.

This is important to understand because fasted training may improve insulin sensitivity (i.e. your cells' ability to respond to insulin and move glucose into cells) if you struggle with insulin resistance or high blood glucose.

During fasted training, hepatic glycogen stores are mostly depleted if no exogenous carbohydrates are supplied.

Prolonged exercise can cause dysregulation of glucose metabolism, which can leave you in a hypoglycemic state.

But what's interesting is that regular fasted exercise can induce specific physiological adaptations that facilitate glucose homeostasis despite having limited availability of hepatic glycogen 1.

This is likely due to a change in fuel substrate selection from glucose/glycogen to fatty acids.


Whether you're looking to gain mass, increase strength, or shed fat, supplements can provide you with the boost you need to get there.

Two of the most common ones we see for fasted training are BCAAs and HMB, which we'll look closer at in this section.


BCAAs comprise three essential amino acids: leucine, isoleucine, and valine. Your body can’t synthesize them and thus must come from an exogenous source, hence why people often take BCAAs while training, especially during a fasted state.

They play a significant role in muscle growth and recovery and are generally a staple for most fitness buffs.

The reason behind this is that for your body to synthesize new muscle proteins, it has to have all nine essential amino acids present.

Of all the amino acids, however, leucine plays the most significant role in stimulating muscle protein synthesis.

It may even have a critical role in signaling pathways involved in protein synthesis, thus giving it a double-duty role 3.

What's more, BCAAs may also help to diminish the effects of DOMS and the extent of muscle damage by lowering levels of circulating creatine kinase (CK) and lactate dehydrogenase (LDH)--two markers of muscle damage 4, 5.

But in terms of taking BCAAs in a fasted state, one of the biggest reasons they're taken is because of the concern over gluconeogenesis.

This metabolic pathway generates glucose from non-carbohydrate sources (i.e. amino acids or fatty acids). This pathway can be stimulated during periods of fasting, low-carb intake, or intense exercise.

As long as you're consuming adequate protein with every meal, it's unlikely that your muscle proteins will be tapped into, but ingesting BCAAs before or during training can safeguard you against that.

Research shows that consuming BCAAs before fasted training can increase signaling pathways involved in protein synthesis 6.

Wondering where you can get a good BCAA? Performance Lab SPORT BCAA supplies the optimal research-backed 2:1:1 ratio of BCAAs made with Ferment-A-Pure technology, all delivered in vegan-friendly NutriCaps®–a clean, convenient alternative to artificial flavors, sweeteners, and synthetics found in most other BCAA supplements.


HMB, or beta-hydroxy-beta-methylbutyrate, is one of the latest and greatest additions to the workout supplement world.

It's a compound produced in the body as a by-product of leucine metabolism and has attracted loads of attention because of its anti-catabolic properties.

By preventing muscle breakdown, HMB can help to increase workload, reduce and repair muscle damage, and improve muscle mass 7.

While you may think having leucine in your BCAAs is enough to reap the benefits of HMB, not so fast.

The problem with relying on leucine for HMB is that most leucine (80%) is shuttled towards protein synthesis, while the remaining 20% is broken down into two compounds: a-ketoisocaproate (a-KIC) and HMB.

But only about 5% of that 20% actually makes it to HMB.

See the problem?

But supplementing with pure HMB is great for fasted training and here's why:

  1. It reduces muscle breakdown: HMB has been shown to stimulate protein synthesis via a specific pathway called mTOR. This ability to synthesize proteins has been linked to stimulation of mRNA translation, muscle cell proliferation, and protein synthesis, along with an expression of insulin-like growth factor 1 (IGF-1) and growth hormone (GH) 8, which are both needed for muscle growth.
  2. It boosts energy: We all know that getting out of bed to do a fasted workout is far from easy, but taking a HMB supplement may help provide your body with more energy by improving fatty acid oxidation, upregulating AMPK (a molecule that plays a role in energy homeostasis), and improving activity of Sirt1 and Sirt3 in adipocytes and skeletal muscle cells (they increase cellular energy stores and maintain cellular energy homeostasis) 9, 10.
  3. Regulating cortisol levels: Cortisol is the stress hormone that can wreak havoc on your performance. Taking HMB in a fasted state may help to blunt the effects of cortisol release by up to 32% 11, but may also boost the testosterone to cortisol ratio in men, which indicates one's state of anabolism.

What's Better For Fasted Training?

If you're looking to stick to fasted training, HMB is definitely the way to go, but it's not to say that BCAAs don't have their place.

While BCAAs have long been the popular choice for fasted and non-fasted training, the problem with them is that you may not be getting the complete picture for muscle protein synthesis (MPS).

Think of it like a light switch. You can turn on the light switch (MPS) all you want, but if there's no electricity (amino acids) running to that switch, you will not get light.

For muscle protein synthesis to occur, you need all the essential amino acids, not just the branched-chain amino acids.

So, suppose you're supplying your body with BCAAs, hoping to boost muscle growth and not eating enough protein post-workout.

In that case, you're going to end up breaking down muscle tissue to supply the remaining amino acids.

However, if you're combining BCAAs with adequate dietary protein, you've pretty much set the grounds for muscle growth.

And if you want to maximize your gains, adding HMB into that equation pre-workout with something like Burn Lab Pro helps to boost energy, preserve muscle mass, and burn fat.

What's not to love about that?

When To Avoid Fasted Training

Keep in mind that there are a few situations where fasted training is not recommended. Avoid training on an empty stomach if:

  1. You are trying to gain muscle mass
  2. You are trying to improve your anaerobic capacity
  3. You are training for an extended period
  4. You're in a session where you need maximal effort

    For people in these situations, it may be counterproductive to train in a fasted state.

    That's because lifting on an empty stomach increases the likelihood of tapping into your muscle proteins as a source of fuel, which is completely counter to what you're trying to achieve.

    As well, you're going to increase the amount of strain on your body, which means you're not going to be performing at your peak and it's going to make it more difficult to recover properly.

    You may also end up with more soreness, which will impede on upcoming training sessions.


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