Agree.

Several times I've attempted to study how the body metabolizes energy, how to lose weight, how to gain muscle, and so on. There does seem to be a huge amount of variability between persons, and I personally found it harder to get decently confident answers about such things than about other complex phenomena like procrastination and happiness.

I will not be writing about metabolism or weight loss or muscle gain anytime soon. Too complicated and not a field of my expertise.