Everything in moderation.
Most keto/paleo diets call for fat to replace carbohydrates, but for folks with IBS [irritable bowel syndrome], fat [from butter or bacon grease or hamburgers etc] will tend to induce some really nasty diarrhea.
OTOH, for folks without IBS, fat tends to induce constipation.
Go figure.
As a man, your two most important nutrients are protein and calcium, for strong muscles & bones. Where I'm assuming you're already getting plenty of Vit C for Scurvy and Vit D for Rickets.
The single most important
factor in the obesity epidemic is simply the calories themselves: Eat
too many calories [in any form] and you gain weight; eat too few and you lose weight.
There's also a ton of evidence that fasting does wonders for your longevititty, and there was even a new study recently which held that fasting could slow the onset of Alzheimer's, and maybe even reduce it after the onset.
And as much SLEEP as you can possibly squeeze into a 24 hour day