Why too much cardio can make you gain fat

Just to be clear before you read on, I am not trying to discourage you to not go out for your usual run, walk, swim or bike ride. Cardio has many health benefits, it is a great way to relax your mind, to get an endorphin (happy hormone) release which makes you feel amazing, especially when exercising outdoors. There is nothing wrong with cardio in moderation. In this blog however, I am referring to using excessive cardio exercise, usually combined with a very low-calorie diet, for the purpose of fat loss.

Unfortunately, it is still a common misconception amongst women, that doing endless amount of cardio daily and following a restrictive diet is the best way to lose fat. They think that if they simply burn more calories and eat very little, it will get them the body of their dreams. Wrong! Cardio might get you results if you are just starting out with your fitness journey, but it is not going to be the best solution if your goal is to shape your body and to keep the weight off for life.

And here is why:

  1. Doing low-moderate intensity cardio exercise only, without any form of weight training, can decrease muscle mass (muscle that would give your body shape!) and as a result slows your metabolism. A lowered metabolism means that your body is not going to burn as much calories during the day as before, which will likely cause fat gain in the long run, especially if you stop exercising and dieting. The number one priority when it comes to fat loss is to build and preserve as much muscle as possible. Muscle is a fat burning tissue! The more muscle you have, the more calories you burn, even at rest, and the easier it will become to maintain your weight. More muscle = higher metabolism = more food without fat gain!
  1. Your body will eventually get used to the same amount of cardio you do daily, and it won’t be burning as much calories during physical activity as when you initially started. Even if it says on the cardio machine that you burnt 300kcal in that session, in reality, it will probably be less than that, due to your lowered metabolic rate, which the machine obviously doesn’t take into consideration. You will eventually reach a plateau and the only way to keep losing weight would be to add more time to your sessions or increase the intensity. But who wants to spend hours in the gym every day just to get skinny? And where is the end to that? 2 hours of cardio a day?
  1. Long duration cardio exercise can elevate the stress hormone cortisol in the body, and high cortisol levels inhibit fat loss. Carrying extra weight around the torso can be a sign of elevated cortisol levels. Stress not only slows your fat loss progress, but also makes you age faster.
  1. Cardio makes you hungry. People often think that they can eat a lot more just because they exercised, and they usually reward themselves with something high in carbohydrates and sugars after a workout. This wouldn’t be an issue after an intense weight training workout however, low to moderate intensity cardio exercise does not significantly deplete energy stores or cause muscle damage, therefore a higher carbohydrate intake is not necessary and it can result in fat gain.
  1. Let’s be honest here. Too much cardio is boring, stressful on the body, not sustainable long-term and not even helping you to get the results you are after. Eventually you will get fed up and stop exercising all together. However, now you are left with less muscle mass than when you started, hence a lowered metabolism, which will very likely result in gaining back all the weight you lost and sometimes even more. And that’s when the cycle starts… After a while, you decide to go back to the gym and start the diet again, but this time it is even harder to lose the weight because you have less muscle to begin with. This is the so-called yo-yo effect. The longer you are in this cycle the harder it will become to lose fat and the more weight you can put on long term.

What can you do?

The key with cardio is not to overdo it and not to rely on it as the main form of exercise for fat-burning. A couple of cardio sessions on top of your strength training can help with your fat loss progress and to stay lean, but your main priority should always be maintaining and adding more muscle to your frame. It will be much more beneficial for you in the long-run if your goal is to shape your body and keep the fat off for good. Building lean muscle increases your metabolism which means you can eat more healthy food without gaining unwanted body fat.