It's not like they all spend 24 hours a day at the gym or adhere to a secret routine. (There are a wide variety of effective methods for building muscle, including low reps with a heavy weight, high reps with a lighter weight, straight sets, supersets, and so on. To put it another way, there is no "best."
Furthermore, it's not because they're using illegal substances to boost their abilities. (There are plenty of ways to bulk up without resorting to drugs, as any drug-free bodybuilding competition can attest.)
The Problem with Bulking and Cutting
When most people decide to bulk up, they go through a period of excessive eating and training. You may know it as "bulking."
A few weeks or months later, they swap places. They may begin to feel insecure as a result of their increased size. Also, they may be self-conscious about their expanding waistlines. They reduce their calorie intake and switch up their workout routine to shed extra weight. We call this stage "cutting."
Most people cycle between these two points of no real progress: bulking and cutting. Why? For the simple reason that starting a new phase continuously undoes the progress made in the previous one.
We've discussed Set Point Theory here on our website. An attachment to one's weight makes it difficult to lose or gain that weight. You discussed its relevance to slimming down in our previous article. It contributes to the difficulty of losing weight and keeping it off.
For Total Calories Per Day
If you only have time to exercise once a week, multiply your goal weight by 10. The multiplier rises by one for every weekly training hour over the recommended minimum. You would need to consume around 2,600 calories per day if you had bulked up to 200 pounds through rigorous training (4 hours per week). That total can be divided among as many or as few meals as you like (two, three, four, five, whatever).
Subtract the calories you get from protein and fat from your daily total, and then divide the result by 4 to get your recommended daily intake of carbohydrates. Keeping with the example until this point, if you had 2,600 calories and subtracted 800 from protein and 900 from fat, you would be left with 900 calories to allocate to carbohydrates. That's 225 calories worth of carbs per day if you divide it by 4.
Your maintenance phase may last anywhere from a few months to a few years, but you should plan for the long haul. Why? Because, once more, you intend for this to become your norm.
Muscle development is a long-term process, not something you should think about in terms of days or weeks. Those with the most muscle and bulk are the ones who stick with training for years on end.