The Simple Math of Weight Loss

 Many people say they have counted their calories for years and it doesn’t work. A lot of people go on diets, meaning they restrict the amount of calories they are eating. Even when people restrict their daily intake to 1,200 calories, they don’t lose weight at any significant rate. Eating only 1,200 calories a day should have most people feeling very hungry. When weight loss doesn’t happen with such extreme sacrifices, it can feel frustrating and like dieting and counting calories doesn’t work. After all, who wants to feel like they are starving day after day without losing any significant weight?

Calories In Versus Calories Out

Putting the quality of food aside, I want to talk about the simple science and math behind weight gain and weight loss. Think of fat simply as stored energy. Then think of calories (cal) or kilojoules (KJ) in your food as units of energy. If we eat more energy than we burn in a day, we will store that energy as fat. This storage of fat results in weight gain. It is important to note that calories don’t just magically appear in our bodies. We have to eat more than we burn off in a day in order to store that excess energy as fat. So in order to loose weight, you have to eat less and move more. 

It ultimately comes down to calories in versus calories out. One pound equals 3,500 calories. So in order to loose one pound, you must burn 3,500 MORE calories than you consume.  

First Step: Calculate Your Basal Metabolic Rate (BMR)

I’m going to explain how this works using a little bit of math. In order to do this we must determine one’s Basal Metabolic Rate (BMR). BMR is in essence telling you how many calories you burn by doing absolutely nothing. It’s the energy you burn in a day just by pumping your heart, breathing, and basic metabolic functions that keep you alive.  You can find great BMR calculators online. These calculators will ask you to enter basic information such as your height, weight, age, and gender. They will then give you a pretty good estimate of your BMR. 

Second Step: Calculate Your Activity Multiplier (AM)

Another thing we must calculate is your level of physical activity. This will allow us to determine the activity multiplier (AM).

Level 1: AM = 1.2 

Sedentary all day long. You may have a desk job or participating in little to no exercise daily. 

Level 2: AM = 1.375

Lightly active. You’re moving around on your feet all day but you aren’t extremely physical. Perhaps you’re walking around and working at a grocery store. You might be doing light exercise or sports 1-3 times per week. 

Level 3: AM = 1.55

Moderately active. Examples may include being a personal trainer demonstrating exercises all day or a garbage man hoisting bins. Perhaps you are participating in exercise or sports 6-7 days per week. You’re pretty physical. 

Level 4: AM = 1.725

Extra active. Perhaps you are a construction worker. You are super physical and performing hard exercise two or more times per day. Maybe you are training for a marathon or triathlon. 

Third Step: Combine your BMR and AM

Now for the next piece of math. When you multiple the BMR by the AM you get the Active Metabolic Rate (AMR). The AMR gives us roughly what a person burns over the course of one day.

Ex. Lindsey is a 50 year old female, 160 lbs and stands at 5’5”. She has a Level 2 activity score. She is consuming 1,400 calories a day. Using the BMR calculator, her BMR is roughly 1,400 calories. This means Lindsey burns 1,400 calories a day if she does absolutely nothing all day long.

BMR = 1,422

AM = 1.2

AMR = 1,422 x 1.2 = 1,706


 Using this math, Lindsey burns roughly 1,700 calories in one day. 

Fourth Step: Calculate Net Calories

In order to calculate your net calories burned or gained, you have to subtract your AMR from the amount of calories eaten in a day. Now when we take into account she is eating 1,400 calories a day:

This means Lindsey only has a net loss of 300 calories in a day. Remember, one pound equals 3,500 calories. This means it will take Lindsey 12 days to lose one pound (3,500 / 300).

Using Lindsey as an example, here is what most people are not acknowledging when they are trying to lose weight: 

  • Lindsey is no longer gaining weight. She wants that scale to go down and therefore feels like she is failing.
  • The scale is slowly going backward. Lindsey is actually slowly loosing weight and the scale is going backwards. However it is not fast enough for her to feel like the diet is worth her time or that it is accomplishing anything. Perhaps when she goes to get on the scale it is that time of the month or she’s had a meal high in sodium (think water retention). Not only may she not see the scale go down, she might see it go up a pound. After a month, maybe she sees the scale go down one or two pounds. This can be infuriating after all that hard work and make a person want to quit. Small incremental change over a period of time is hard to feel.


The Key To Losing More Weight 

Here is the key: We have to get the calories burned HIGHER in order to accelerate weight loss so it can be seen and felt. Otherwise it doesn’t feel like it's working. How do you do that? Exercise! This is why a large part of weight loss has to include exercise. You don’t want to starve the weight off nor is it healthy, as it can be incredibly damaging to your entire body, organs, and well being. You have to exercise!

So let’s use Lindsey as an example again. But this time, let’s say she is burning 400 calories a day via exercise. This also means her activity level has increased. Her calorie intake is still 1,400 per day. 

BMR = 1,422

AM = 1.375

AMR = 1,422 x 1.375 = 1,955

AMR + 400 calories burned via exercise = 2,355 

1,400 - 2,355 = 955 calories burned a day! 


This means Lindsey will burn roughly one pound every 4 days (3,500 / 955). This is pretty close to two pounds a week.

So you can see calorie-counting does work but in order to see the results at the rate you want you have to exercise to boost your calories out. There is no way around this. Ultimately it comes down to calories in versus calories out! 




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