Honestly, I’m extremely tempted to try to create a statistical model of the metabolic cycle and attach it to a physical profile, to calculate calories and so forth. There’s a pretty hefty investment of time and effort involved, but you could create a pretty simple monte carlo simulation for each of the processes involved in turning food into energy and waste.
You don’t need to know how the brain works to understand its gross nutrient intake, and if you understood that in context of the rest of the body’s consumption, it might be possible to optimize for a given set of activities - I want to be optimally mentally alert, and I want to work out as well, so how do I adjust the micro and macro nutrients for workout days?
Obviously it’s not a simple problem, because of the tremendous number of chemical interactions that happen when you undergo heavy physical activity, or intense thought. You could simulate what happens when you add caffeine, or nicotine, etc, and show short term effects. With this type of simulation, you could predict long term macro-effects for well understood processes, like chronic toxicity, bone and muscle growth, and so forth.
Anyone want to chip in on such a project? It’d be mostly research, I’m almost certain Wikipedia alone would suffice, but I’d bet there are huge communities that discuss the bits and pieces to endless detail, so a large amount of the hard work has been done - it’s a matter of searching it out and simulating it in sequence.