Can Cardio Make You Fat?

Sabina Skala

Sabina Skala is a certified and highly experienced Strength and... read more

Can cardio make you fat? The first answer that springs to mind may be “of course not”, but it’s more complex than that. Read on to find out why,

You gain fat when the energy you put in your body is greater that the energy you spend.

Man Doing Cardio

However you look at cardio – it is energy expenditure. So, why do many people struggle to lose fat if they are spending hours running or doing other aerobic activities? Some actually notice increase of fat tissue around their waist or glutes, what is the reason behind it?

But, before starting any aerobic activity click here to know how to choose the best running shoes that will help you reach your goals quicker. 

There are instances when doing long, medium intensity cardio can cause an increase in body fat. In the lack of resistance training, long term, medium intensity cardio leads to the loss of muscle mass, which lowers the metabolic rate and the amount of calories burnt at rest and during effort.

Why do we lose muscle tissue when working at low or medium low intensity? Muscles are “metabolically expensive” tissue. They burn calories and need nutrients and oxygen. Therefore long distance endurance athletes don’t have impressive musculature, as it would not be efficient for the body to carry a huge muscle mass. 

Marathoner vs Sprinter

Your body will adapt to your training. It wants to get as efficient as possible at the activity you train for. We  need to understand that if we want to get better at long slow cardio and long endurance races, our goal cannot be 5 % of body fat and a super ripped physique – it is just not going to happen.

Low Intensity Cardio is Not Ideal for Weight Loss

Going through regular long, medium or low intensity work, you become more efficient at the task but at the same time as your muscle mass decreases, you burn fewer calories.

If your goal is changing body composition, you may need to reconsider the need for medium intensity aerobic activities.

People with elevated cortisol levels from chronic stress (this can mean anything that hinders recoverry, for example lack of sleep, stressful job or personal life, or bad nutrition) are less likely to lose body fat from long duration cardio activities. This type of cardio can even cause the cortisol to go up,. This will stress the body systems even more and cause the body to store more fat. When cortisol is high, the cells become resistant to insulin. The body is then unable to reach to body fat for energy. Due to hormone imbalances (an increase in ghrelin,which sends the “I’m hungry” signal to the brain, and decrease in leptin, which supresses hunger) people with higher cortisol often have cravings for sugary foods. The growth hormone and testosterone (men) or progesterone (women) levels are low, resulting in fat gain particularly in the waist area.

This way, cardio can indeed increase or keep the body fat.

If you are new to training, long form cardio can be of benefit to improve cardiac function, vascularity of the body and build a solid foundation that will take you towards strength and higher intensity training. Long, medium intensity cardio causes adaptations that you cannot accomplish with High Intensity Training. Lower intensity activities stimulate vascular network development around the working muscles. This increases oxygen and nutrient transport to the muscles.The type of cardiac muscle adaptation with lower intensity activities is called eccentric cardiac hypertrophy. The heart adapts to the training stimulus by stretching its walls. As a result, the resting heart rate (RHR) and the working heart rate gets lower and cardiac efficiency increases. The heart has to do less work to pump the blood to the muscles and the aerobic energy production gets better because the muscles will receive more oxygen. To achieve this type of adaptation you must spend at least 30 mins performing aerobic activity where your heart rate doesn’t go above 120 – 150 bpm- may vary for individuals. 

If, on the other hand, you already are in a pretty good shape looking to improve your body composition further, long, slow cardio may not be for you. Instead, focus on strength training and add High Intensity Interval Training to your routine.