10 Apr , 18

Training while fasted

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fastingTraining while fasted is a hot topic in the current world of fast fitness… see what I did there?

The understanding of current concepts and trends often require a more comprehensive look than what is delivered in a 90-second video. While the topic of training while fasted seems on the surface that it is revolutionary… it isn’t

Why only a few short weeks ago it was gospel  that you had to eat every two hours in order to “keep the fat furnace firing” – then along came stupid old science which punched  that myth into utter oblivion (sorry if you have your fit bit set for feeding time alarms every 120 minutes).

The idea of fasting, and then training while fasted, became much more appealing to a large percentage of people.

As a lifestyle, it seemed to fit with people’s daily regimen.  Most people don’t leave enough time for themselves to eat breakfast before work anyways. Equally as many people don’t even have an appetite in the morning, such as my wife and my kid, thus the strategy of intermittent fasting matches their lifestyle pretty easily.

Here are the most popular strategies which are in no specific order:

• 16/8 → 16hrs of fasting every day, with an 8-Hour “feeding” window

• 20/4 → 20hrs of fasting every day, with a 4-Hour “feeding” window

• 24hr fast → Picking one day per week to not eat anything for 24hrs, normally a Sunday

Each of these has their own positives and negatives, but a comprehensive review of intermittent fasting is not what we are here for today. I want to say right from the hop here that intermittent fasting does have unique benefits, but like everything in health and fitness, they are very context specific.

Make no mistake about it, I am not for or against intermittent fasting, I am simply an observer of the literature and will make recommendations based on a person’s situation

Now, the notion of training while fasted has unique benefits, but if your trainer recommends that you hop on the tready for 50 mins in the FBZ and sip BCAA’s you need to run the opposite fastingway.  (FBZ is just a cool way to say fat burning zone… I think its a diagram on the treadmill)

This is how the convo will shake out:

“Well, you are in a fasted state since you haven’t eaten in 8+hrs so you will be primarily using body fat for energy use. This way, we can drop pure body fat. But, since we don’t want to lose any muscle mass while you do this, you should also have some BCAAs during your morning fasted cardio session”.

Begin punching holes in 3…2…1 –

From big picture calorie balance, energy substrate use, the rate of muscle degradation, and intracellular signalling, there is a number of holes in that theory. But to make this a more digestible rant and not get too far off-track here, let’s just pick on BCAA use during your fasted morning cardio.

Training while fasted means… Training while fasted

With BCAA’s you’re not fasted anymore, I’m sorry, but you’re not. BCAA’s contain 4kcal per gram whether they admit that on the label or not.

fasting alpha nationBCAAs are also readily available forms of energy substrate that can be used to fuel physical activity, especially in a fasted state. For the required and potentially beneficial effect of fasted cardio you actually have to be fasted. No BCAA’s, no cream and sugar in your coffee.


But here’s where this goes off road right.

The whole idea of fasted cardio is to maximize the amount of mobilized fatty acids floating around your bloodstream (since you have been fasting for an extended period of time, glucose is not as readily available as it would be if you had a pre-workout meal) so that you can burn more of your own body fat during this session, and not glucose.

BCAA’s elevate insulin levels in the body which literally block fatty acid mobilization. Research is very clear that even extremely low levels of insulin completely blunt acute fat mobilization/oxidation.

Any amount of BCAA’s that you consume during your fasted cardio is going to far exceed the amount of insulin required to block fatty acid mobilization.Can fasted cardio be beneficial? Potentially, but if you’re not actually fasted and you’re also elevating insulin levels during the process you’re kind of missing the point.

While I could explore this across a number of different scenarios, for this short piece I want you to take away the fact that training while fasted means exactly that.  Don’t compromise a potentially beneficial training strategy because someone has made an off the cuff comment without it being well researched.


Todd Lamb is one world's most trusted sources of Health and Fitness information and programming. He has dedicated his life to the service of others having served as a member of the Royal Canadian Regiment in the Special Service Force and as 17 year veteran Police Officer with 10 years on SWAT and 4 as a Team Leader. Todd is dedicated to transforming the lives of 1,000,000 men through honest science based information backed up with years of practical experience in Tactical Operations. Todd is a Best Selling Author of multiple best selling fitness programs and the book STAND APART

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3 thoughts on “Training while fasted

    1. Todd Post author

      Branch Chain Amino Acids – they are in your food however there are several BCAA supplements available. If you get enough protein in your diet you don’t need them.

  1. Winnie

    In the morning first thing i drink a 24 oz glass of pure lemon juice (about 3 the) two capfulls of apple cider vinegar and one packet of truvia n hot ta water. Does this automatically take me out of fasting mode? I don’t drink coffee at all it makes me sick. My first meal of the day is usually about 8 hours or more later. I sleep anywhere from 7 to 9 hours a night having stopped eating about 2 hours before bed which is usually a piece of fresh fruit. I kinda eat what I want but not to excess, what’s in season usually dictates what fruits or veggies I eat. I have my own garden for veggies and in the winter I have a pretty big indoor garden of fresh herbs. Parsley is one of my favorites. I eat fish at least 2 times a week, but do sometimes snack on pickled herring in dill sauce in the evening. I have lost 56 lbs over the last year and am hoping to continue doing more. Background; I worked midnight shift in hospital in medical imaging for a level one trauma hospital for many years. Had to quit working to take care of my mom with Alzheimer’s till she passed and when that happened my many injuries over the years left me fairly disabled to go back to work. I gained a lot of weight feeling sorry for myself and have suffered from cronic arthritis since the age of 22, I am now 67 . My range of motion is very limited but am feeling better since having lost the weight.


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