Sitting makes the brain thin and the body fat

New research has established that sedentary behaviour not only contributes to obesity and associated diseases, but results in thinning of brain structures that are important to memory.

Bike riding will not only make you physically healthy, but can also provide the exercise needed for brain health.

Researchers at the University of California, Los Angeles, gave the study subjects a high resolution MRI scan providing a detailed look at the medial temporal lobe, or MTL, a brain region involved in the formation of new memories.

The researchers found that sedentary behaviour is a significant predictor of thinning of the MTL and that physical activity, even at high levels, is insufficient to offset the harmful effects of sitting for extended periods.

MTL thinning can be a precursor to cognitive decline and dementia in middle-aged and older adults. Reducing sedentary behaviour may be a possible target for interventions designed to improve brain health in people at risk for Alzheimer’s disease, researchers said.

Thinning of the brain’s medial temporal lobe is of concern to researchers as it is linked to poor episodic memory. Shrinkage of the brain’s memory centres is particularly pronounced in dementia.

The study subjects reported average sitting times of three to 15 hours a day. After adjusting for their subjects' ages, the researchers found that every additional hour of average daily sitting was associated with a 2% decrease in the thickness of the medial temporal lobe.

The research suggests that, compared to a person who sits for 10 hours a day, someone of the same age who typically sits for 15 hours would have a medial temporal lobe that's 10% thinner.

And that, said study leader Prabha Siddarth, represents a lot of missing brain.

If you're sitting for long periods of time, it seems that that factor — not physical activity — becomes the more harmful or more significant measure of your fitness. Even for people who are physically active, sitting a lot seems to be bad for your brain."

That's consistent with studies of sitting's effects on such health measures as heart disease, diabetes and mortality, she said. "Now we're finding it in brain atrophy," she added.

The results were published this week in the journal PLOS One.

The brain, of course, relies on adequate supplies of oxygen and nutrients to maintain itself and resist the depredations of aging. If sitting too long is compromising those supplies, then it stands to reason that our delicate cortical structures will have trouble maintaining the volume and density they had when we were young, Siddarth said.

For those looking to keep their brains plump and their memories sharp, Siddarth said the message is clear: Get up. Pace while talking on the phone, dance with your headphones on, take a walk at lunch. And if you’re at a computer all day, set hourly alarms that remind you to stand and march around.

And get on the bike rather than sit in the car.