How much is too much cardio?

The more, the better – a common belief is that if you want to lose weight you should do cardio training. However, it is becoming increasingly apparent that endurance training can quickly backfire. As with many things in life, the right dosage is key.

It all starts with small steps. 30 minutes of daily cardio units quickly turn to 60 minutes, 60 minutes to 90 and then one cardio unit in the morning and evening. In the beginning, scale and mirror quickly show first signs of success and the pants and/or dress finally fit again. But there comes a point where physical success becomes less apparent and the guilt due to “dietary sins” needs to be compensated with exercise. The consequence? Half an hour longer on the cross-trainer. And thus starts a vicious cycle: more and more cardio and less and less food. The frustrating part is that the body does not reach the desired shape, but rather shows negative results. The reason? The thyroid.

Studies very clearly show that excessive cardio training can switch off the production of the thyroid hormone T3 in women. T3 is the most prominent metabolic regulator, which is responsible for the efficiency of the cells and body temperature regulation. To put it simply, when the T3 hormones are at a normal level, the body also burns enough energy to keep warm and to maintain the muscle function with moderate efficiency. Too much of the thyroid hormone (hyperthyroidism) makes the body work less efficient and weight gain becomes impossible. Too little of the T3 (hypothyroidism) allows the body to accumulate more body fat – regardless of how physically active a person is.

And that is exactly the problem. The apparent lack of success often leads to more excessive and exaggerated training. Due to too much cardio and especially steady-state-cardio, at up to 65% of the maximum heartbeat, women tend to maneuver themselves into the state of hypothyroidism.

We humans are an adaptive species and can withstand long-term stress thanks to our survival instinct. High energy consumption sends out danger signals to the body, which in turn switches into « survival mode » and the metabolism is lowered to save energy. Instead of burning the desired body fat, this is stored for the protection of the body. And it gets even worse: the body continues to hang on to its fat cells even after training. In addition, too much muscle mass is lost due to too much steady-state cardio (more than 20 hours a week), since the body takes the energy mainly from the muscles and not from the unwanted fat cells.

What to do?
First, take a break from the treadmill. The body takes time to bring its T3 level back into balance. The belief that excessive cardio training is the solution to a well-shaped body is a myth. On the contrary: too much and incorrectly performed cardio damages the thyroid gland, inhibits fat burning and leads to muscle loss. Weight training especially the combination with short HIIT units is a much more effective way to reach the desired athletic figure.