Why is exercise good for the brain?

Physical activity raises heart rate and increases blood flow to the brain, delivering more oxygen and glucose. It also triggers release of brain-derived neurotrophic factor (BDNF), a protein that supports the survival and growth of neurons and connections between them. A well-known 2011 study found that a year of regular aerobic walking increased the size of the hippocampus, a memory centre, in older adults by about 2 percent. Exercise also reduces stress hormones over time and is linked to lower rates of depression and anxiety. The WHO recommends adults get at least 150 minutes of moderate activity a week.