Why health and fitness really is in your blood

Hard exercise forces a molecular explosion in your blood.

If exercise were a drug, as doctors like to say, then everyone would prescribe it. Since it is not a drug, though, how does it have such a transformative effect on health?

A study suggests that it achieves this through a “molecular explosion” in the blood. The research, which documented in greater detail than ever before the changes in the blood following exercise, also found that a simple test of these molecules could show how fit you are.

“Exercise has all these incredible benefits,” Michael Snyder, an author of the study by Stanford University, said.

HENRY ZEFFMAN

From heart attacks to dementia, keeping fit seems to protect against most diseases and ensure a longer life.

It was only midway through the 20th century when the first studies began to show the benefits of exercise and even today, the mechanism is unclear.

“What we don’t really understand is what drives that at a molecular level,” Professor Snyder added. He and his colleagues measured the levels of tens of thousands of different molecules before and after exercise. They found that whatever made exercise so beneficial was not simple. “Half the molecules in your blood change, just from an intense bout of exercise,” he said.

The study, published in Cell, involved monitoring the blood of 36 people after an intensive session on a treadmill. Professor Snyder said the researchers had “the first glimpse of the comprehensive role” that exercise played in affecting the whole body. “It’s like a symphony, a whole orchestra of molecules,” he said.

They found that the systems affected included those involved in repairing the body, boosting the immune system, and metabolising food. “We have some hints from this as to key regulators that may be affecting all biological processes involving health,” he said.

In the blood taken before exercise there was also an indicator of how people would perform. The results of a VO2 max test, a traditional and exhausting test of fitness, were predicted by the levels of just 12 molecules.

Previous studies looking at molecular changes in the blood after exercise have suggested that the work could eventually lead to an “exercise pill” that could recreate the benefits of working out without the tedious bother of actually doing it – gain without the pain.

Professor Snyder said that he was wary of suggesting that that might be possible soon.

“I said this was like a symphony, and that’s exactly what it is. If you wanted to make an orchestra you wouldn’t just throw together all the instruments and hope they would produce a beautiful sound. The real key is understanding how all of this is put together in a co- ordinated fashion, to produce beautiful music.”

Unfortunately, for now, the only guaranteed way to make that molecular music is to be your own conductor and get off your couch for a jog.

The Times