5 Surprising Things That Age You

What it ages: Your brain

The science: Our brains naturally lose white matter with age, but researchers from the University of Cambridge found that the brains of middle-age overweight and obese people had the same amount of white matter as healthy people 10 years older than them. Being physically unfit in middle age was also linked to smaller brain size 20 years later, according to research in Neurology.

What you can do: Get regular exercise (the U.S. Department of Health and Human Services recommends at least 150 minutes of moderate aerobic exercise, or 75 minutes of vigorous exercise, per week) and manage your weight to help keep your brain at a healthy size for your age.