Life expectancy may be predicted by the size of a tiny structure at the center of a cell that called the nucleolus. The smaller the size the longer the lifespan. Food restriction and exercise have been shown to shrink nucleoli in humans.

Nucleoli form ribosomes, the protein factories of cells. It is thought that as the nucleolus gets smaller, it is better at balancing the need to grow with the need to repair and correct mistakes such that repairing and preventing damage become better.

It is still not known whether the reduced size of the nucleolus is responsible for the increased life expectancy or is it just biomarker without playing a causal role. More research is needed to determine this.