This RD Explains What Your Basal Metabolic Rate Is and How It Affects Weight Loss
To lose weight, you may have read that you need to burn more calories than you take in. This basic math, calories in vs. calories out, seems easy enough to comprehend — until you realize that everyone's calorie needs are different. Just how many calories do you burn in a day?
Although the exact answer is hard to pinpoint, you can make a pretty good guesstimate based on your daily activity level and how many calories your body burns on its own. It all starts with your basal metabolic rate.
I recently got my body assessed using an InBody Test, which sends electrodes through your body and calculates your BMI, body fat percentage, and basal metabolic rate, among other stats. Confused by what my 1,386 basal metabolic rate number actually meant, I asked personal trainer and registered dietitian Jim White, ACSM, owner of Jim White Fitness and Nutrition Studios, to break it down for me.
"Basal metabolic rate is the amount of energy a person needs to keep their body functioning at rest," he said. "Therefore, if you were to sit all day long and keep your body in a rested state, you would burn 1,386 calories." This number accounts for your body's caloric needs to perform its life-sustaining duties, such as brain function, heartbeat, digestion, and so on. It doesn't include the basic daily activity I perform that burns calories: walking to and from the subway to work, my workouts, standing at my standing desk, etc.
To figure out how many calories I need to eat a day to lose weight, I must first understand how many calories I burn a day on average, which is called total energy expenditure. Total energy expenditure is calculated by taking an activity factor and multiplying it into your basal metabolic rate.
My activity factor is about 1.4-1.6, which accounts for someone who is moderately active: moderate exercise four to six days a week. And since I have no injury factor, that means my energy expenditure is around 2,079 calories a day.
"To translate this number to weight loss, consuming less than 2,079 calories would be negative energy balance, which could potentially lead to weight loss, and likewise consuming more than 2,079 calories would be positive energy balance, which could potentially lead to weight gain," Jim explained. "Consuming around 2,079 calories a day would help keep this person at the exact same weight."
If I want to lose a pound a week, I need to eat at a 500-a-day calorie deficit since one pound equals 3,500 calories. So for me to lose weight and eat in a healthy calorie deficit, I need to shoot for about 1,579 calories a day. Now, time to bust out my food journal and get to tracking!