Basal Metabolic Rate

I was pondering the mysteries of the BMR and plateaus in weight loss recently. As I had blogged recently, the weight loss trend, though negative still, was easing in the slope of the trendline.

I shared this with my wife and she said a line that I've heard from others before...exercise is needed. You need to exercise to lose the weight.

Let me first make it clear that what I'm saying here isn't a criticism of my wife or what she was telling me; I've heard this line several times from different people and sources.

But it doesn't add up to me.

The basal metabolic rate is basically a rough estimation of how many calories your body burns if you just sat on a couch all day. It's the calories your body burns to keep you alive...calories to maintain everything from heartbeat to brain function to even the amount of filled fat cells in your body.

If you have a surplus of calories over that amount, you gain weight. If you're below it, you lose weight. Fat contains 3500 calories per pound...a surplus or deficit of 3500 calories over a period of time means you gain or lose a pound of fat, more or less...of course, certain things dictate if you're losing or gaining fat or muscle tissue and water, etc., but overall that's a basic five thousand foot overview.

Right now the online fitness site on which I keep track of my weight and food intake has an estimate of my BMR at about 3,300 calories/day. Yes, the heavier you are, the higher the BMR. The site estimates that at my weight this morning...376 lbs...if I wanted to weigh about 360 by April 30th, I'd need to restrict my calories per day to 1,697 to lose .47 pounds per day.

Okay. That's the basic math and basic estimates.

Now for plateaus ... it doesn't add up. BMR numbers are estimates that are taken from your age, weight, height, gender, and activity level (I tell it that I don't do anything...that way I don't have to factor in X hours per day of exercise to hit a certain number. If I exercise, it's a bonus.) There are factors that can't easily factored in, like variations in our metabolism. That's why I said it was a simplified overview.

But I'd have to be a mutant to have an estimated BMR of 3300 calories, take in about 15 to 16 hundred per day, and not lose weight. There are variations, but that difference is huge, by a factor of two!

The body, when it comes to weight, is like a rubber bag. We can't "generate" food. You gain weight by taking matter in and processing it. You "excrete" energy by sweating, breathing, giving off body heat, going to the bathroom...you can't simply generate matter magically from thin air. The *closest* I can think of to having that happen is your skin absorbing water when you're sitting in the tub too long, and even then your body excretes it relatively quickly.

Gaining weight means your body has processed food and retained it, usually in fat in the case we're trying to avoid. You retain water also which can make you look like you gained more weight; when I eat four pickle slices or a lot of mustard, the sodium content gives me a one or two day sudden pound and a half weight gain that then disappears just as quickly (if I don't have more pickles or mustard).

If you are taking in fewer calories than your body needs in order to maintain basic life functions, it must tap energy reserves...fat or muscle...to compensate.

A popular bit of wisdom is that you must exercise because after awhile your body adjusts to your reduced caloric intake. But again...if you're way under your BMR, it can't generate energy from nothing. Your body may slow intake, it may retain water for awhile, but it must eventually continue losing weight if you aren't taking in a surplus of energy.

I never found a definitive reason the body plateaus other than the body apparently has set points where it likes trying to hold a weight level. Advice like exercising, or even making a significant boost in caloric intake for a day, more or less seems to do something goofy to your brain chemistry to alter it's behavior through a plateau so it decreases the time it takes to begin...hopefully...losing weight again.

If someone has a definite way to explain this phenomena feel free to share. Otherwise, I'm going to stick to what a different doctor many many years ago told me. "You're fat because you eat more than you burn. Eat less or burn more. That's the only way to lose weight."

All the diets out there advocating things like eating for your body type, avoid fats, eat fats but avoid carbs, eat soup for a week then peanuts and beer, these berries will turn your metabolism into a fat-burning machine, the bible diet...all these things...are fancy ways of making money by getting people to eat less in what is usually an unsustainable manner. I might even be able to make money by marketing a chainsaw diet. A few moments with a chainsaw and one leg later, you've lost twenty pounds or more!