Key Points * The nutritional value of chocolate bars should be based on the nutritional value of the low energy dense late Paleolithic human diet to help reduce mental ill health, obesity, and other postprandial insults. * Current chocolate bars have a high energy density (>2 kcal/g). * Cocoa can be sweetened by the addition of calorie-free Purefruit™ (Tate & Lyle) monk fruit ( Siraitia grosvenorii ) extract. PUREFRUIT™ is approximately 200 times sweeter than sugar and has exceptional stability. * The energetic cost of the assimilation of chocolate can be increased by increasing its protein and fibre content. * Self-assembled, water-filled, edible nanotubes that self-organise into a more complex structure, possibly a 3D network of nanocellulose, could be incorporated into chocolate bars to lower their energy density to <1.6 kcal/g. * Durethan® KU 2-2601 packaging film enables the water content of chocolate bars to be increased without reducing product shelf life. * Aquatic biotechnology can provide all the nutrients needed to make chocolate really nutritious.