According to the advice given by The Physical Activity Guidelines for Americans, released in 2008, To maintain substantial health benefits for public health and welfare.
The advice that for healthy adults, adults should workout for 150 minutes or hours and 30 minutes over a period of a week of moderate-intensity. For a vigorous-intensity aerobic physical activity, one should 75 minutes for a week.
In humans, the brain accounts for ~2% of the body weight, but it consumes ~20% of glucose-derived energy making it the main consumer of glucose (~5.6 mg glucose per 100 g human brain tissue per minute.