Specialization and cognitive skills
I remember Lyle saying that specialization will win out athletically instead of being a jack of all trades, i.e. power lifting vs Crossfit. The average powerlifter who specializes can pick-up Crossfit and do well but a Crossfit guy can't do the opposite.
At least I think I'm remembering what he said correctly.
Does this apply to cognitive skills? For example a physicist being able to switch over to something easier like biology?
Half-way measures don't get very far. You can only do one thing well at a time. Trying to gain muscle while losing fat will result in failure.
Get to 10% bodyfat first while lifting weights heavy 3x a week with reduced volume. Two weeks maintenance. Bulk up slowly (1 lb weight gain per week max), focus on getting stronger, measure body composition changes often.