The amount of calories used by thinking about a task is almost insignificant compared to baseline thinking about "nothing". IIRC it's in the tens of kcal per da

The amount of calories used by thinking about a task is almost insignificant compared to baseline thinking about "nothing". IIRC it's in the tens of kcal per day. The difference vs sleeping is much larger, but still pretty much inconsequential. On the order of 100kcal I'd think. The vast majority of the calories you eat in a day are used just keeping your biological machine ticking over. Most of what you do is lost in the noise of your BMR. Of course this excludes physical exertion, but that's not really part of this scenario.