1. If sitting it is bad for your posture, back etc. Lack of exercise could be an issue.

2. If thinking hard it might cause fatigue in the mind, burnout etc.

3. If working in a stressful environment, e.g. working with dicks then longer exposure to this could cause psychological problems.

A good hack would be to do a job where you can stand / walk for at least some of the time.

E.g. a job where you do some stuff on a whiteboard, or present a lot in front of people, or can pace around and think would help.

A job where you don't work with dicks would help.

A job where you are not doing novel stuff all the time or working on complex code bases or issues all the time would help.

So my hacks are in the choice of job where you work the long hours, rather than along the lines of drinking soylent etc.

HOWEVER

Why do you desire to work long hours? This seems odd to me.

If it is just to get better results, then just aim for better results. If you run your own business this might entail setting up systems that take you out of the picture.