Can I focus on one area, or does coaching have to cover everything?

You can absolutely focus on one area.

Some clients primarily want help with nutrition. Some primarily want physical training guidance. Some want help with emotional regulation, stress, relationships, or clearer thinking. Any of those can be a legitimate starting point.

The integrated model does not mean that every domain receives equal attention at all times. It means that we do not pretend the domains are isolated.

If your main goal is fat loss, we may still need to consider stress, sleep, food environment, habits, expectations, and relationship context. If your main goal is emotional steadiness, we may still need to consider physical exercise, nutrition, sleep, caffeine, routines, and environmental friction.

The starting point can be narrow. The lens should not be.