ShareShould you do cardio in a “fasted” state?
Last week, I had this question come in…
“Kate, do you think I should do cardio on an empty stomach in the morning to burn more fat?”
Well cool cats, whether or not cardio on an empty stomach can speed up fat loss is a hotly debated topic in the fitness industry. Some folks believe fasted cardio is more effective at burning fat, while others believe it will decrease your performance and limit fat loss.
Today you will get the lowdown on what scientific research has to say about this, and if fasted cardio a legit way to burn more fat, or just another load of BS.
And when I see fitness sites post articles with absolute garbage like this…
“Fasted cardio works, if you’re using performance-enhancing drugs to protect your muscle. Otherwise it stinks.”
Ha! I just can’t help but get my rant on. Seriously?! It was missing this hashtag… #WorstSupplementPlugEver 
Now back to business.
Why did this fasted cardio idea get so popular?
In 1999, Bill Philips introduced his Body-For-Life program that promised a body transformation in 12 weeks.
In his cardio chapter, while HIIT was his preferred method, Phillips also introduced the theory that performing aerobic cardio first thing in the morning on an empty stomach will maximize your fat loss.
His rationale was as follows:
A prolonged absence of food in your body reduces the circulating blood sugar, causing stored carbohydrate (glycogen) levels to drop. That leaves your body no choice but to use fat, rather than glucose, to fuel your workouts.
Plus the low insulin levels associated with fasting are conducive to fat breakdown, meaning there are more fatty acids available to be used as energy during the workout.
So ever since… Fasted cardio been popular with physique competitors and bodybuilders striving to get as lean as possible.
And it’s not without merit. While one study from Poland shows cardio on an empty stomach burns more fat DURING exercise – I’m not 100% convinced. (1)
The research indeed shows that fasted cardio can increase fat utilization during exercise compared to performing cardio in a fed state – except this only occurs at a very low intensity for 60 minutes.
Big whoop.
Who cares if you burn more fat IN your workout? In the end, it doesn’t matter.
Research also shows that people who burn fat during their exercise session actually burn less fat the rest of the day.
Fat burning is NOT as immediate process. It occurs over the course of days, not hours. So you need to consider the entire 24 hours, not merely your workout.
So Should You Perform Cardio on an Empty Stomach?
No. I’m sorry to say, but the whole 5am “zombie cardio” before breakfast is just another waste of your time.
Here’s why…
#1: The “afterburn effect” is minimal
Fasted cardio makes even less sense when you take into account the impact of excess post-exercise oxygen consumption (EPOC), which is commonly known as the “afterburn effect” and represents the number of calories burned after training. This is what cranks your metabolism for hours, even days post workout and burns FAT.
And get this: eating before exercise promotes substantial increases in EPOC. (2) And better yet, as you burn more carbohydrates during your workout, your body will burn more fat post exercise.
High fives all round.
While you may burn more fat during your workout on an empty stomach, your overall workout output will be lower. Plus your body’s ability to burn fat post-exercise will be compromised.
Did you ever try a HIIT session on an empty stomach? Bet it wasn’t fun and you hit the wall pretty quickly.
To perform at a high level, your body needs a ready source of glycogen. Deplete those stores and say bye-bye to a quality, high intensity session.
Overall, you will burn fewer calories both during and after exercise in this instance, diminishing total fat loss.
To Cardio or Not to Cardio before breakfast?
The strategy to do cardio on an empty stomach is misguided, especially for physique athletes.
At best, effects on your body composition won’t be any better than in a fed state, and you’ve wasted all that time.
So if you should eat… what is best to consume before training?
The answer depends on a number of factors, including intensity and duration of training, and the timing of previous meals before your workout.
Don’t get too fancy. Grab a piece of fruit or a handful of nuts to help your body use efficient energy sources to power your workout. Avoid the devilish high fructose corn syrup and you’re good to go.
You need to think about the BIG picture. Always choose sustainability and energy over anything else. You’re on a transformation journey, which as surprising as it sounds – is not ALL about losing weight and belly fat.
Your goal is to get “better”. Better at training, better at recovering, better at eating healthy nutritious foods that fuel your body to perform at optimal levels – and the weight loss is an awesome side effect.
=> BOOST Performance and Results with High Intensity Interval Training
Fuel your workouts to go hard and burn carbs, so that you crank your afterburn effect and burn more fat later.
Think big picture!
Your Coach,
KV
References:
1. Zoladz JA, Konturek SJ, Duda K, Majerczak J, Sliwowski Z, Grandys M, Bielanski W. Effect of moderate incremental exercise, performed in fed and fasted state on cardio-respiratory variables and leptin and ghrelin concentrations in young healthy men . J Physiol Pharmacol. Mar;56(1):63-85, 2005
2. Lee YS, Ha MS, and Lee YJ. The effects of various intensities and durations of exercise with and without glucose in milk ingestion on postexercise oxygen consumption. J Sports Med Physical Fitness 39: 341-347, 1999
