Mental Workout

Do you use more energy when you're thinking really hard?
Did Einstein stay lean by burning calories with his brain?

Need to lose some flab? Sit your big butt down with a math book-and feel the burn. The human brain is a 24-hour workhorse. While you´re thinking, millions of neurons fire messages back and forth to each other and to the various tissues in the body. These neurons need fuel, consuming a full 75 percent of the blood sugar from the liver and 20 percent of the body´s total used oxygen. Here´s how your neurons feed: Astrocytes-the cells near the capillary walls in your brain-suck energy-rich glucose from the bloodstream and convert it into a form that the neurons can soak up. The neurons then use it to fuel the production of neurotransmitters and, eventually, conscious thought. â€The more energy an area of the brain wants, the more glucose that part of the brain will break down,†explains neurologist Harry Chugani of the Children´s Hospital of Michigan. â€So yes, if you´re thinking really hard and really struggling with your thoughts, the neurons in the frontal lobes of your brain will be burning a lot more glucose.â€

Simply to survive, your brain requires a tenth of a calorie per minute. Compare this with a walk to the doughnut shop, when your body burns approximately four calories a minute. Kickboxing zaps 10 calories a minute. And when you´re hunched over a crossword puzzle? Your brain is blasting through a respectable 1.5 calories a minute. Pass the Cheetos.