Do you reach for a cookie or other healthy snack while working or studying?
First of all, intellectual mind burns more calories and, secondly, likes sweets very much.
In my favorite book “Thinking, Fast and Slow” Daniel Kahneman explained that when a mind is engaged in analysis or learning, it is influenced by our human, primary system of behavior, and it so happens that this system is a fan of desserts.
It follows that mental effort is not an excuse but a scientifically explained reason for reaching for sweets. In addition, it only confirms that you are intelligent, capable and put a lot of effort into tasks you work on.