There is this horrible misconception in our society about fat loss. A lot of people think that if you starve yourself and do two or three hours of cardio each day, the fat is just going to melt off. Actually, performing too much cardio will put your body in a catabolic state and burn hard-earned muscle. The loss of muscle will not only reduce strength, but it will also slow down your metabolism. If your metabolism slows down too much, you'll have a tough time burning fat.
There's no exact answer for how much cardio is too much. But if you're not a distance runner, anything over 60-70 minutes per day is likely counterproductive—especially if you aren't consuming enough protein or calories to support the daily caloric expenditure. In order to build or maintain muscle, you need to eat enough food.
SYMPTOMS OF CARDIO OVERLOAD
Too much cardiovascular training will also lead to injuries and over-training issues like aches and pains. You can also suffer from consistent bouts of fatigue and mood changes. Too much cardio can also make your cortisol levels rise, which may suppress your immune system. Often, marathon runners experience colds and respiratory infections after they race because of their higher cortisol levels. If you're experiencing any of these symptoms, it's probably a sign you need to cut back the cardio.
Working out is supposed to be fun; it shouldn't be some long, arduous chore. If you are in the gym for more than an hour per day doing aerobic training, you're probably overtraining. If you're not in the business of marathon running or long-distance biking, this much cardio will take you 10 steps backwards instead of 10 steps forward.
If you're not suppose to be doing long bouts of cardio training, what should you do?Research shows that high-intensity interval (HIIT) cardio is particularly good for getting rid of stubborn abdominal fat, including the dangerous accumulations of visceral fat.
Although the exact mechanisms of how high-intensity cardio trumps steady-state cardio aren’t fully understood yet, scientists have isolated quite a few of the factors:
Increased resting metabolic rate for upwards of 24 hours after exercise.
Improved insulin sensitivity in the muscles.Higher levels of fat oxidation in the muscles.
Significant spikes in growth hormone levels (which aid in fat loss) and catecholamine levels (chemicals your body produces to directly induce fat mobilization).
Post-exercise appetite suppression.
And more…And as if all that wasn’t enough, keeping your cardio sessions shorter means you better preserve your muscle and strength, which is ideal for optimizing body composition.
I recommend a very moderate amount of high-intensity interval (HIIT) cardio–no more than 4 sessions per week, and no more than 25 to 30 minutes per session.
It's always good to remember that more is not always better. Be smart about your training. Don't forget to wear that heart rate monitor. Keep it hard and efficient to burn fat, and most importantly, preserve muscle.