Parameters that determine a man's health:
โข Muscle mass and muscle strength
โข Low Body Fat Percentage
โข Hand grip
โข Waist to Height Ratio
โข Gait cycle
โข Sleep
Eat 400 calories above maintenance daily with 2g protein per kg of bodyweight. Follow a progressive strength program and add weight to the bar each week.
Weigh yourself daily, track the weekly average, and bump calories if the scale stalls. At this rate, you'll probably gain ~1.6kg/month expect about half of that to be actual muscle: