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Resting bmr and and squishy math

I run into a lot of issues when trying to prescribe diets to my clients. Clients often ask me what to eat, how often to eat, how many calories to eat, etc as if there is a magic formula for a perfect set of abs or a tight booty. And the truth is, it depends. It’s an un satisfying answer and there’s a lot of room to fudge the numbers.

So BMR or basal metabolic rate is an ESTIMATE of how many calories you’d burn if you didn’t do anything during a given day. If you laid around in bed, awake, this is roughly how many calories you’d burn. The keyword here is roughly. Bmr takes into account a few different things. Age (older means slower), gender (sorry ladies, men burn more), height as well as your weight to come up with an estimate of how many calories you’d burn if you were basically a vegetable that blinks.

So, to keep the math simple, let’s say that for a 200 lb man, we get a bmr of 2000 calories. Now most people, outside of certain government bureaucrats, don’t just sit on their ass all day technically constituting as alive. Some people are going to have higher or lower activity levels and this is going to affect your metabolism. This is calculated by something called an activity multiplier.

The activity multiplier tries to estimate your total calorie burn to give you a tdee or total daily energy expenditure. Now a sedentary individual (pretty much anyone not in a coma) is going to have a multiplier of about 1.2, so that person burns about 2400 calories a day. Think of a desk worker and you have a good idea. One level up is “lightly active” at 1.375. Lightly active is defined as light exercise 1-3 times per week. Hopefully by now you are starting to see some issues with this system by now. I’ll skip a couple levels and go all the way to highly active, meaning someone who works out strenuously twice a day, their multiplier is 1.9, which gives us about 3800 calories in our example.

So the glaring problem with this model is the activity level. Let’s assume there is no much thing as hyper or hypo-thyroidism and assume that anyone who actually exercises and eats correctly will lose a defined amount of weight. He do we define very active? Exercising vigorously 2 times a day for 6 out of 7 days. But what is vigorous exercise? Weight training? Hill sprints? Sweating on an elliptical?

What about a severely obese person? Is their idea of strenuous exercise different than a heavyset power lifter? Each level has a difference of roughly 300 calories in this model which multiplied over 7 days is 2100, or over a half a pound of fat for anyone trying to lose fat. So someone trying to safely lose a pound a week might only see 1/2 lb which doesn’t even register on most scales!

Another flaw with this model is the idea of muscle damage. Take two athletes of similar mass, build, and fat percentages but that practice different sports, let’s say a marathon runner and a flyweight boxer. Now if both these athletes run 10 miles, who do you think is going be more sore afterwards? The boxer obviously, he will suffer more muscle damage and thus require more calories to repair.

Another thing to consider is that if someone is dieting, they tend to be tired. So daily activity starts to go down. You take the elevator instead of the stairs. You forgo a hiking trip and decide to watch tv and let your body recover. Little things here and there to avoid exertion because you are dieting.

All these little factors contribute to the inaccuracy of tdee. Tdee is only useful if it’s closely monitored against weight loss or weight gain. When you decide to go on a calorie counting diet, you have to match it up against a your actual results. If you’re losing weight, good. If you’re not, drop another 200 calories a day and see what happens in a week.

Or you can do what I do. Focus on eating more vegetables and leans meats and lift a Mack truck every morning. Eat when you’re hungry. Drink a lot of water. And follow a sound lifting program that amps up intensity over time.

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