Too much cardio can definitely be a bad thing.
One of the things I have encountered most in training has been the idea that “cardio is king.” Many times I have had a long conversation about the dangers of over-training and the injuries and metabolism slowing effects too much cardiovascular exercise can have.
Issues too much cardio can create:
- While cardio does burn fat, it also burns muscle.
- If you burn too much muscle, you can actually slow your metabolism.
- Too much cardio can actually prevent you from reaching your goals at the gym.
I am not saying you should stay away from cardio; far from it. I am however saying doing cardio for an hour a day by itself is not necessarily the best way to reach your fitness or weight-lifting goals. Livestrong suggests cardio should not exceed 150 minutes for an entire week. QBX Fitness says too much cardio is definitely a bad thing. They even say that too much cardio can actually cause you to start GAINING fat.
Bottom line: keep your cardio a bit shorter and add some muscle-toning weight training.