After finishing a mentally draining task such as a taking a test or finishing a big project you might feel as though you've run a marathon. Your brain is tired, which often makes your body feel tired. This type of activity contributes to a small calorie burn, but not enough to aid in weight loss.
Mentally Draining Activities
Activities that tax your brain require additional energy, but not to such a degree that you'll burn hundreds of calories. The extra focus needed to finish such activities make you feel drained, but your physical energy reserves aren't being tapped, which means your calorie burn is small. Examples include taking the SAT test, passing the bar exam or pulling an all-nighter to finish an important paper. If you are trying to lose weight, overloading your brain isn't going to produce results and might make you too worn out to engage in healthful forms of exercise.
Mental activity boosts your metabolic rate, which is necessary for extra calorie burn. However, thinking only uses up about 20 percent of your resting metabolic rate, according to David A. Levitsky, a professor of nutrition and psychology at Cornell University. This equates to about a 300 calorie use by your brain per day for all mental activity, taxing or not. Thinking extra hard during the day burns little additional calories, Levitsky reports.
How Many Calories
The actual calorie burn that occurs with mentally draining activities is only about 20 of the 300 calories your brain uses each day, according to Levitsky. This calorie burn occurs because when you work on solving a problem, the glucose uptake in your brain increases. Once you stop working on the activity, your levels return to normal, stopping the extra calorie burn. Levitsky doesn't recommend thinking hard as a legitimate way to drop unwanted pounds.
You might notice food cravings while you're involved in a mentally draining activity that is particularly hard. For example, you might want candy or soda when you're working hard on a big project at work. These cravings aren't a result of burning additional calories, but more likely stem from stress, which taxes your brain's reserves of natural sedatives, according to the International Guide to the World of Alternative Mental Health. As a result, you experience the need for emotional eating. Most people turn to junk food on these occasions. Additionally, if you forget to eat or are tired during an activity, you might crave sugary foods for an energy boost. If this is the case, you might experience weight gain because junk food has more calories than thinking burns.