Scientists have churned out a bunch of studies lately about why exercise is important for brain health and may even help to lower your risk of dementia. Now, new research breaks down a specific chain reaction that happens in the body when you work out—and this discovery may even help prevent dementia.

A poor response to insulin can lead to dementia, so the idea that exercise can help prevent this by possibly boosting insulin signaling is significant, Malin said. While more research is needed, these findings reinforce the idea that physical activity could be an accessible, low-cost way to support long-term brain health.

Beyond calorie burning, Saga highlights that swimming has been proven to decrease blood pressure, enhance lung capacity and flexibility, improve sleep quality, and slash the risk of dementia and stroke by 30 percent, and type 2 diabetes by 40 percent. University of Warwick experts also endorse swimming as one of the "best" exercises for seniors.

Keeping active throughout life—particularly before the age of 50—leads to changes in the brain that could help stave off dementia, according to a study published in the journal Brain Communications .

New research found that working out starts a chain reaction that can lower your risk of dementia. Here's exactly how it works—and how long it takes.