I want to be Lean & Mean. How do I determine the minimum amount of calories on a daily basis required to do this?
We find ourselves sitting cross-legged and still with a clear, uncluttered mind like a buddha in a room of about average (18C–20C) ambient temperature.
Under such circumstances, most of us will burn up somewhere in the vicinity of between 1600 kcal and 2400 kcal (based on age, height, sex, amount of total and lean body mass and some other variables) in a 24-hour period.
This is called your RMR, or resting metabolic rate. If you want to nail it down a little more precisely for yourself, you can become a guinea-pig in a laboratory enclosed in a device that will determine the ratio of respiratory gas (CO2 vs O2), providing an exceedingly accurate calculation to you. Here is a scan of one that I had done at thea few years ago pictured above as an example.
RMR is not exactly the same as BMR, or basal metabolic rate, but close enough. A nice, useful little freebie that is usually thrown in along in the printout you get is data that will also indicate what the ratio of your RMR is derived from fat vs. carbohydrate. I think mine cost me around $50 and took about an hour to do. If you have it done at a high end, profit-oriented establishment, it will probably cost you a lot more. I understand that there are now some relatively accurate handheld consumer devices on the market like the Body Gem that will do the same job, but I haven’t had much experience with them.
So, to get back to your original question, let’s give it a provisional answer at this stage. You ought to be able to get by with a 2500–2800kcal intake (although I would experiment with a macro caloric ratio of something like 30–40% P, 20–40% F, 20-30% CHO until I could get a good idea of what worked). But what results you get will also depend heavily on your daily activity level.
As a kilogramme of muscle is worth approximately, 2000 kcal, you won’t need a large caloric excess in order to gain and maintain a little muscle. If, on the other hand, you’d like to gain another kilo of fat, that might cost you a more generous 7500 kcal of extra intake.
A general rule of thumb is that the faster you gain weight, the higher the chance that the new weight gain will be composed of a higher percentage of fat. The corollary to this rather bothersome & annoying fact is that the faster you lose weight, the greater the likelihood that most of the weight loss will be from that nice, lean body mass that you worked so hard for.
The mean bit, we’re going to have to leave that up to you to figure out.