by Oscar Saucedo
That’s one of the questions I get quite often. Because I get that from fitness beginners, advanced athletes, personal trainers, and veteran fitness enthusiasts, I think it’s a good topic to touch on this month.
First of all, we will establish that it’s the total calories that you eat per day that determine whether you gain weight or lose weight. Very simply put, if you have a calorie deficit, which means you burn more calories than you eat, you will lose weight. If you have a calorie surplus, or you eat more calories than what you burn, you will gain weight. So it is clear that it is important to account for calories going in and calories going out, much like you account for the money in your bank account.
Second, to begin to figure out how much to eat per day, you must figure out how many calories you burn in a day. Your basal metabolic rate (BMR) is how many calories your body burns in a day just to maintain life. If you were to sleep all day, you will burn a “base” amount of calories. BMR varies from person to person. But to begin to estimate your BMR, a simple way it to take your lean body mass (LBM) and multiply it by 10.
Please notice that I did not say to multiply your weight by 10. It’s your lean body mass that matters. Fat is metabolically inactive (it just sits there and jiggles), so I don’t count it. But your LBM, on the other hand, burns calories. Find an InBody body fat assessment scale or a certified personal trainer that is proficient using body fat calipers to calculate your body fat percentage and your lean body mass. As an example, a 200lb man with 20% body fat is 40lbs of fat (200lbs x 0.20 = 40lbs) and 160lbs of LBM (200lbs total – 40lbs of fat = 160lbs LBM). So the man in our example has an approximate basal metabolic rate of 1600 calories per day (160lbs LBM x 10 = 1600).
The next step depends on whether you want to gain weight or lose weight. To gain weight, you must eat more than what you burn. If this is your goal, it’s safe to eat a number of calories equal to double your BMR and determine how that works for you over the next 2 weeks. But most of you will be looking to lose weight. We will take our example above and calculate how to help him lose 1 pound of body fat per week.
It takes a calorie deficit of 3500 calories to burn 1 pound of body fat. Because of this, I suggest aiming for no more than 1 pound of fat loss per week. Over the course of 7 days, that 3500 calorie deficit would divide into a 500 calorie deficit per day. Having covered that vital information, we can now move on to calculate how many calories our example burns in a day. We begin with the base amount—his BMR. From there, it depends on how active he is in his job. An office job will have very little physical demands and will add maybe another 300-400 calories burned to the day (most people can add about 25% to their BMR). A job in construction, carrying roof shingles up a ladder all day, will burn significantly more calories in a day. But I cannot cover everyone in this editorial, so we will assume our example has an office job.
Now we are at BMR + daily activities = total calories burned. The example here is 1600 + 400 = 2000 calories burned per day. Add in an hour of necessary exercise (should be about 500 calories per hour), and he burns 2500 total calories on days he works out and works his job. We can now say he should eat 2000 total calories per day (2500 – 500 calories to maintain the calorie deficit = 2000 calories).
Not enough space here to get into the foods that should be included in that 2000 calories. We will save that for next month. I apologize for some of the technical stuff. But if you’re interested in learning how to change your body—or help others—this is just a starting point!