Yearn for the fat burn! But do those “fat burn” buttons on exercise machines really live up to their names? What about the cardio button?
Seems pretty straight forward, right? You push the fat burn button and voila! The fat melts away.
Push the cardio button and you build a ticker like a thoroughbred racehorse.
Uh, yeah right…good luck with that.
So what’s the deal? Will the fat burn button eject that junk from your trunk? And will the cardio button give the Tin Man a heart?
Well, the answer is – it depends. Let’s have a closer look.
High intensity vs. low intensity exercise?
In exercise physiology, we have something known as the Respiratory Exchange Ratio (or RER).
This is where we measure your expired carbon dioxide and inspired oxygen in a laboratory. The ratio gives us an indication of how much fat or carbohydrate you’re using as a fuel source at a given intensity.
In general, lower exercise intensities use more fat and higher intensities use more carbohydrate (glucose).
The energy substrate chart illustrates this principle.
That’s what happens in the lab, but how does it translate to losing stored body fat in the gym and looking great for that class reunion?
Here’s where it gets tricky so pay attention.
While there are numerous factors which impact your ability to lose weight, still, at the end of the day, it is ultimately a numbers game.
If you burn off more calories (kJ) than you consume, you will lose weight. Eat more calories than you burn off and you gain weight.
I jokingly tell my exercise physiology students to tell their clients, “use the fat burn button if you want to stay fat. Use the cardio button if you want to lose fat.”
“Fat burn” vs. “Cardio” exercise per unit of time: the smoking gun
Generally speaking, a higher intensity sustained for a longer duration will best maximise energy expenditure, resulting in a greater calorie (kJ) deficit, and more likely lead to the most weight loss “bang for the buck.”
For example, walking on a treadmill at 1 mph (1.6 kmh) for 10 minutes (low intensity) will use proportionally more fat as a fuel source. But the trade-off is that it will burn comparatively fewer overall calories (kJ) than walking on a treadmill at 5 mph (8 kmh) for 10 minutes.
The latter 5mph (8 kph) is higher intensity and will use proportionally more glucose as a fuel source BUT, more importantly, will also maximise the overall calorie (kJ) expenditure PER UNIT OF TIME and lead to the greatest caloric deficit.
So the take home message from the above discussion is that, to maximize fat loss, you need to work out at higher intensities for longer durations.
But WAIT, there’s more!
Don’t go anywhere yet! That’s not the end of the story. You might be scratching your head saying, “well heck, I haven’t exercised in 30 years. I can’t do high intensities yet. I get short of breath just walking to the mailbox.”
Establish your fitness foundation
You need to ease into exercise. Even if you can only do a few minutes at a time at a very low intensity, this is still a good thing. Do what is known as interval training.
You do short bouts of activity with little rest periods in between. Then gradually wean your way onto longer, more continuous durations while reducing the number of exercise bouts.
Fat burning interval training
Once you have your fitness foundation in place, then you can to start challenging yourself to do higher intensities.
For example, if you’re doing a 30 minute continuous walk at a moderate pace, then try interspersing short 1-2 minute intervals at a higher intensity. After your intervals, slow down to your previous speed and use this as an active recovery.
When you’re ready again, add in another interval. Your goal is to walk at the highest intensity that you can sustain for a given period of time.
Bottom line on fat burn vs cardio buttons
When it comes to the fat loss game, forget the exercise equipment fat burn and cardio buttons.
I suggest using a manual setting so you can customise the workloads to your individual fitness needs. Work your way to the higher intensities as appropriate and then hold it there for a while.
In the grand scheme of things, forget about which fuel source you’re using. The key is to maximise your energy deficit.
While everyone is looking for the secret to permanent fat loss, the secret is that there is no secret. You still have to eat less, move more (perhaps add in some resistance training), and remain consistent in your efforts.