Moderate Plus trips require you to have higher fitness levels than you would have on a moderate level trip. During these trips, you will trek in higher altitudes and for longer hours than you would in Grade 1, 2, or 3 trips. Your trip will involve trekking in altitude of around 5000 meters but not above that. You should be able to trek for around 7 hours every day on average. The trekking can last 10 to 15 days.
Therefore, you need to have good levels of fitness to complete the Grade 4 trips... Even if you have a lifestyle which is passive, a few months of physical training will help you prepare for this trip.