There’s been a lot of hoopla concerning cardio’s “damaging” effects on your ability to burn fat. I’ll be the first to admit I fell down this rabbit hole as well. Much of my earlier knowledge came from sources who were obsessed with gaining as much muscle as possible versus the typical everyday Jane and Joe who just want to lose a little bit of fat and tone up. The story evolved into “too much cardio will destroy your resting metabolic rate (RMR)”. In other words, the more cardio you do the slower your RMR will become over time. While too much cardio can have other negative effects, just like everything else in over abundance, this couldn’t be further from the truth.
Twelve studies were conducted with varying age groups, body compositions, training backgrounds, and diets to determine if cardio workouts negatively impact your RMR. Nearly ALL of the studies came back with the same conclusion: cardio does NOT damage your RMR. However, it does NOT increase it either.
One of these studies compared collegiate level wrestlers and swimmers and found that neither groups training routine negatively affected their RMR. That’s right. One group who’s routine was almost entirely anaerobic and one group who was entirely steady state cardio and there was no significant differences in RMR (when factoring in fat free mass).
Another study was conducted over a 12-month period (for fitness and health related studies, 12 months is more than long enough to see if training regimen or diet can affect one’s health and body composition). This 12-month study included a group of 17 sedentary individuals who conducted 45 min. jogging/walking routines 3x week. The results? There was a reduction in body fat (roughly 3.5%) but NO change in the RMR. So, fat loss does not increase RMR either.
So, what does change your RMR? Very simply, if you eat too little, train too much, and LOSE LEAN MUSCLE then your RMR will drop! If you want to increase your RMR then you need to increase your lean muscle mass. Strength training anyone?
In Summary: Increase your lean muscle mass to increase RMR. Cardio can help reduce body fat but does not increase RMR, nor does it cause any damage.
STAY FIT MY FRIENDS!