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What Is A Calorie Deficit?

Let’s start at the beginning- how do you lose weight? If you ask 100 people you may get 100 different answers to this question. Some will suggest keto, one will say that a juice cleanse worked for their neighbor, another will mention the South Beach Diet, and yet another will suggest endless hours of cardio. All these answers are correct, but not in the way you think.

The only way the body can mobilize fat for energy (burn fat) is if the body is in a calorie deficit. This deficit can be created by diet, exercise, or ideally a combination of the two.

At rest, the body burns a certain number of calories to maintain all the processes that keep us alive; this is your basal metabolic rate (BMR). You will expend these calories each day regardless of what you eat or what activities you perform. For simplicity purposes, let’s say your BMR is 1,500 calories. If you were to eat exactly 1,500 calories you would net 0 calories for the day. If you eat 2,000 calories you would net 500, and if you ate 1,300 calories you would be in a deficit of 200 calories.

To burn a single pound of fat requires a cumulative calorie deficit of 3,500 calories. From our previous example, if you are in a calorie deficit of 200 calories every day it would take 17 days to burn a pound of fat. We can speed this process along in a few ways: prescription medications that increase your BMR (such as Adipex), deepening the calorie deficit by burning additional calories through exercise, and slowly bringing calories down to further the deficit.

There are many ways to determine your individual BMR, some of which are superior to others. The gold standard would be a body scan; this is invaluable when you are beginning a weight loss journey. A body scan not only estimates your BMR but it breaks down your scale weight into fat, muscle, water, and more. The body scan will calculate your BMR fairly accurately and follow up scans will help show where your weight loss is coming from. If you’re interested in getting a body scan, shoot me an email at janey@afteroursobgyn.com and I can help direct you to a facility that offers them. While less specific, online calculators for BMR are also useful (I’ve linked my favorite one below).

Now that we’ve determined your BMR, let’s begin creating a calorie deficit. If you’ve never counted calories before, start with tracking 3-4 completely normal days of eating. The easiest way to do this is by using a free app (MyFitnessPal, Chronometer, LoseIt!, Lifesum, etc.). Tracking a few days will help you understand where you currently are and give us a good idea of how best to get you into a deficit. Let’s say your 4 days looked something like this: 1780, 2120, 1690, 1840. The average of these 4 numbers is approximately 1850 calories; this will be our starting point. Set this as your calorie goal in your app and try to get as close to this number each day as possible. As you feel able, decrease your goal each week by 100-200 calories until you get near your BMR. Add in some activity and you have your deficit!



TL; DR

Basic formula for weight loss: calories in< calories out (calorie deficit)

For the body to use fat for energy you must be in a calorie deficit

Diet, exercise, or a combination of both can be used to create a deficit

To determine how many calories you need to eat to create a deficit, begin with calculating your BMR and tracking a few days of normal eating, adjust from there according to your goals


BMR Calculator: https://legionathletics.com/tools/bmr-calculator/


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