Stress is not just bad for you because of cortisol. Scientists showed that being stressed also makes the body produce myostatin, a protein that powerfully inhibits muscle growth.
Stress: Worse Than We Thought
Stress is a killer, as they say. And when people think of stress and its negative effects – psychological and physical – they tend to think of cortisol, the ‘stress hormone’.
We’ve written about cortisol at length, and while we’ve been at pains to make it known that this hormone is necessary to survival, modern conditions have made elevated stress and cortisol levels an acute part of most people’s lives. In the long term, elevated cortisol is catabolic, meaning it leads to the breakdown and loss of muscle tissue, something we’re definitely trying to avoid.
However, a little-known study from 2010 shows that it’s not just cortisol that’s having this catabolic effect when you’re under stress. Elevated stress levels also lead to increased production of myostatin, a protein which inhibits the production of muscle.
Scientists performed experiments on mice in which different groups of mice were subjected to conditions of varying stress. They placed mice in a different cage every day of the week (indicated by ‘CS’ below) or put them for a short period each day in a straitjacket (‘RS’), a situation which mice – unsurprisingly – find extremely stressful.
After a week, the muscle mass of both groups had decreased, but by most in the mice that were straitjacked. Below are the results for the tibialis anterior muscles and the soleus muscles of the mice.
The researchers noted that both the CS and RS mice, i.e. the stressed mice, started to produce myostatin after the first day, with the RS mice producing the most (see below).
To test whether myostatin was playing an important role in the process of muscle loss, they repeated the experiment with genetically modified mice that did not produce myostatin.
A comparison of the musculature of a normal wild mouse and a mouse that has been genetically modified not to produce myostatin
The results (below) clearly showed that, when stressed, the genetically modified mice did not lose mass in the same way as the non-genetically modified mice. The role of myostatin, thus, was confirmed.
What This Means
Clearly, this is further evidence that stress will, quite literally, kill your gains. The broader implications, though, are that stress may be as important a factor as bad diet or lack of exercise in the current obesity crisis.
“Decreases in lean muscle mass may contribute to a shift in body composition that can promote obesity”, the researchers write.
“A loss in lean muscle mass decreases the amount of metabolically active tissue available for oxidative breakdown of energy substrate.”
“In addition, a decrease in skeletal muscle mass in response to psychological stress may also predispose skeletal muscle to greater likelihood or severity of injury.”
Remember: muscle is metabolically expensive, meaning that the more you have, the greater your body’s requirement for calories. If you lose muscle, your body requires fewer calories and, as a result, it’s easier to overeat and thus put on weight.
This is one why reason why, in the long term, resistance training is a better way to stay in shape than performing endless cardio, as we explore in this article.
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