If you feel like you've done everything to lose weight — keto, intermittent fasting, Whole30, fitness plans, counting macros — and still aren't seeing the scale budge, it's understandably frustrating. After all, putting so much time and effort into meal prep and reading up on the latest diet trends can be exhausting, especially if you don't see any results.
In reality, losing weight boils down to a simple science: burning more calories than you take in. This calories-in, calories-out calculation may seem simplistic, but it does get a little more complicated when you realize that not everyone's bodies burn calories the same.
Calculating Basal Metabolic Rate and Total Energy Expenditure
To find out how many calories you burn a day, you need to know your total energy expenditure, or TDEE. It starts with finding your basal metabolic rate (BMR), which you can get measured with a machine like the InBody Test, which sends electrodes through your body and calculates your BMI, body fat percentage, and basal metabolic rate, among other stats.
You can also do a math equation to find your BMR using the Harris-Benedict formula based on your total body weight, height, age, and sex. It's a little more complicated, but it's more accurate than quick-and-dirty formulas found online. For a woman, the calculation is:
BMR = 655 + (1.8 x height in centimeters) + (9.6 x weight in kilograms) - (4.7 x age in years)
For a woman who is 30, 5'6" (167.6 centimeters), and 150 pounds (68 kilograms), her BMR would be: 655 + 301.7 + 653 - 141 = approximately 1,470 calories a day.
From there, you multiply your BMR by your activity level: 1.2 if you're sedentary, 1.375 if you do light exercise one to three days a week, 1.55 if you do moderate exercise six to seven days a week, 1.75 if you're very active (hard exercise every day or exercising twice a day), and 1.9 if you're extra active (hard exercise two or more times per day).
So for that 150-pound person who is moderately active, it would be: 1,470 x 1.55 = approximately 2,280. That's about how many calories your body burns on any given day. To lose weight, you would have to create a calorie deficit.
How to Find Out How Many Calories You Need to Lose Weight
"One pound is equal to 3,500 calories. Therefore, if someone was looking to lose one pound per week, they would need to cut their daily calories down by 500 calories per day," registered dietitian and personal trainer Jim White, ACSM, owner of Jim White Fitness and Nutrition Studios, told POPSUGAR.
If your TDEE is in fact 2,232, to lose one pound a week, you would have to eat 1,780 calories a day to eat in a healthy calorie deficit and see progress on the scale. Ultimately, this formula is just a guideline; you should consult with your doctor or dietitian to determine your exact calorie needs.