Metabolism, Math and Calories… Making sense of it all

Most of us have at least a rough idea of what a metabolism is - the rate at which your body burns energy. When it comes to losing weight, one of the first things we think of is restricting calories. With fewer calories to burn, your metabolism can work on fire bombing fat instead. Well, something like that anyway.

But in reality, there’s more to your metabolism than that. And understanding how your metabolism works will help you get a better handle on this whole healthy lifestyle thing. Beyond the dreaded calorie restriction (ugh).

Ready for your crash course in why crash diets are a weight loss no-no? Here we go!

your basal metabolic rate

Guess what! If you lie on the couch without moving a single muscle (Netflix binge, anyone?), your body will still burn calories. The amount your body burns in 24 hours of inactivity is called your Basal Metabolic Rate, or BMR, and can represent 80% of the energy you burn a day!

Why are you burning so many calories if you’re not moving? Because you’re still breathing. Your heart is pumping. You’re regulating your body temperature. You are digesting. Your kidneys are functioning. The list goes on! Simply maintaining life in your body requires energy, in the form of calories.

Usually, when trying to lose weight we try to restrict our intake as much as possible on the account of not doing enough activity, completely disregarding our BMR... Big mistake! Giving your body fewer calories than it needs to function on the most basic level can actually slow down the weight loss process, since your body won't be able to spend the energy required to maintain itself.

So how do we know what our BMR is?

calculating your BMR

Most health professionals use an equation to calculate your BMR. I know. Calorie restriction and math. Double ugh! Don’t worry. There’s no quiz at the end.

One frequently used equation is called the Harris Benedict equation:

  • For men: BMR= 66 + (13.7 x kg) + (5 x cm) – (6.8 x yrs) Or BMR= 66 + (6.23 x lbs) + (12.7 x in) – (6.8 x yrs)

  • For women: BMR= 655 + (9.6 x kg) + (1.8 x cm) – (4.7 x yrs) Or BMR= 655 + (4.35 x lbs) + (4.7 x in) – (4.7 x yrs)

Equations take into account gender, weight, height and age, but none of the many other factors that influence BMR. For that reason, these equations cannot be 100% accurate and, in practice, follow-ups are necessary to adjust to your requirements.

Remember, BMR is only the amount of calories your body burns in order to function at the most basic level. It doesn’t consider any physical activity. So unless you are a diaper-wearing couch potato with a fridge at arms length, you are likely burning more calories in a day than your BMR.

why this matters

You never want to restrict calories to lower than your BMR when trying to lose weight. You need to eat. Even if you do nothing but watch the grass grow, you require calories to literally keep your blood pumping. Over-restricting your intake can negatively impact your overall health and long term ability to lose weight.

Ideally, you want your body to function at its full potential and burn as many calories as it can. Cutting out a whole food group (such as carbs) cuts out all the nutrients that come with that group. Not only is this unhealthy, it can actually decrease your metabolism, making it harder to lose weight down the road. We definitely don’t want that!

Essentially, to achieve healthy, long term weight loss (with minimal math homework) you want to stay above your BMR and nourish your body with all the macronutrients, vitamins and minerals it needs to thrive.

Remember, cutting back is one thing. Restricting yourself so much that you’re barely keeping the lights on is something else entirely. So go ahead. Eat carbs;-)

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