Eating less could help you remember more, researchers have found.
Skipping dessert and having an after-dinner coffee instead could also be good for your brain, as well as your waistline.
The news comes from an Italian study into "calorific restriction" - the idea that near-starvation rations boost health and extend life.
Scientists have long known of the phenomenon, but have struggled to work out just what it is about severely cutting calories that improves health.
Researcher Giovambattista Pani decided to focus on a protein called CREB1 that is known to be important to memory and learning.
In experiments on mice, he showed that cutting calories boosted learning if the animals could still make CREB1. He also showed that cutting calories boosts the amount of the protein made in the brain. The animals' calorie count was only cut by 25 to 30 per cent. In human terms, this equates to about 600 calories a day.
A cup of tea or coffee may also be beneficial, with studies crediting caffeine with upping the amount of CREB1 made in the body. The work by Dr Pani, of the Catholic University of the Sacred Heart in Rome is detailed in the journal Proceedings of the National Academy of Sciences.
Dr Pani said: "It is just 25 to 30 per cent fewer calories. It is like not eating a cake at the end of the meal. This gives us a tool to better investigate this brain circuitry and try to figure out more drugs that do the same. We are trying a couple of compounds right now on animals but it is at a very preliminary stage."
Keeping the brain young could be of huge value in an ageing population. Alzheimer's and other forms of dementia affect more than 800,000 Britons, and the number expected to double in a generation.
Dr Pani said: "Our findings identify for the first time an important mediator of the effects of diet on the brain. This discovery has important implications to develop future therapies to keep our brain young and prevent brain degeneration and the ageing process. Our hope is to find a way to activate CREB1, for example through new drugs, so to keep the brain young without the need of a strict diet."