Exercise Doesn’t Burn Fat By Itself, Like, At All
Maybe the title is a slight exaggeration, but not by much.
Exercise doesn’t burn a lot of calories under the best of circumstances ( think 100 kcal/mile during a marathon ), hence why exercise is a bad idea if it is going to be your only means of trying to reduce fat mass.
When I tell my clients this, it blows their minds. When I tell a new trainee this, it REALLY blows their minds.
In a recent study titled “Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults” showed that cardiorespiratory exercise was “superior” to resistance training with regards to reducing fat in obese men. This made the rounds on message boards and even had a science daily feature with a nebulous title.
You can’t trust an editorial at science direct, as you don’t get the whole story. As a result you have to look at the whole study, which on the balance is well done. However let’s look at the changes that show “proof” of how bad lifting weights is for fat loss. The before and after fat mass and lean mass changes between resistance training (RT) and aerobic training (AT) before and the change after the length of the trial:
RT = Fat mass 34.3kg −0.26
AT = Fat mass 34.7kg −1.66
RT = Lean mass 54.4kg 1.09
AT = Lean mass 53.3kg −0.10
RT = Fat % 38.8 −0.65
AT = Fat % 39.4 −1.01
Now a couple of things to note here based on those results:
1. This was an 8 month trial and all they can manage was a 3.52lb (1.66kg) loss with cardiorespiratory training alone? Yes that’s “8 times” the fat loss but I could do that with an obese person in 2 weeks with a dietary intervention. To repeat: Exercise isn’t good at fat loss in the absence of dietary intervention.
2. When you account for the recomposition effect of the RT increasing muscle mass (where the AT group lost muscle), their body fat percentage loss was nearly identical.
This study doesn’t tell us anything new regarding exercise and fat loss. Dietary intervention is still king with regard to fat loss and AT only has statistical superiority in this particular study, as nobody who lives in the real world is getting excited about 3.52lbs of fat lost over 8 months in clinically obese individuals. It makes for a great headline but so what?
So what is exercise good for? A whole bunch of other things that diet cannot improve in healthy human beings. Getting mad at exercise for not causing fat loss is like getting mad at Red Lobster for not serving Chicago deep dish pizza; your expectations do not match what it is actually capable of providing.
Skyler Tanner is an Efficient Exercise Master Trainer and holds his MS in Exercise Science. He enjoys teaching others about the power of proper exercise and how it positively affects functional mobility and the biomarkers of aging.