The Math Behind Weight Loss and Weight Gain

Weight management can be boiled down to a formula — but can it really be that simple?

Every clinician, at some point in their career, has been asked about weight management. This is an issue that plagues populations across the world, not only frustrating these people trying to do their best to manage weight, but also leading to dangerous health issues when not controlled effectively. So often, people turn to fad diets or other “quick fixes,” which are usually unproven, or only temporary options, when what people really need is: A Mathematical Lifestyle Change

The Math

Let’s keep things simple. If you BURN more calories than you EAT, you lose weight. If you EAT more calories than you BURN, you gain weight. 100% of the time. Of course, there is a little bit more nuance to this. Let’s dive a little bit deeper….

In order to burn one pound of fat, you would need to be in a 3500 calorie deficit. To put that in context, if you wanted to lose one pound every week, you would need to be in a 500 calorie deficit every day for all 7 days (because 7 x 500 = 3500).

Now all we need to do is figure out how many calories you can eat in order to stay in that 500 calorie deficit!

The total amount of calories a person burns in a day can be sorted into 4 categories:

• BMR: Basal Metabolic Rate

  • How many calories would your body burn if you were to do absolutely nothing in a dark room for 24 hours

  • Avg 1300-1600 for adult women

  • Avg 1700-2100 for adult men

  • This value can vary DRAMATICALLY with different health conditions

• NEAT: Non-Exercise Activity Thermogenesis

  • How many calories does your body burn from normal, non-exercise daily movements (tapping your foot, typing on a keyboard, shaking your head, etc.)

  • Avg NEAT can vary between 2 people by up to 2000 calories/day

• EAT: Exercise Activity Thermogenesis

  • How many calories does your body burn from exercise every day

  • Based purely on how much exercise a person does every day (can be 0 calories, can be thousands)

• TEF: Thermic Effect of Food

  • How many calories does your body burn from digesting the food you eat every day

  • Proteins burn about 20-30% of their original caloric value

  • Carbs burn about 5-10% of their original caloric value

  • Fats burn about 0-3% of their original caloric value

So maybe this is a little bit more complicated than I originally let on….Let’s simplify further.

The Simplification

While knowing the exact numbers and values to your specific BMR, NEAT, EAT, and TEF would give you the exact number of calories you can eat in a day, it’s almost impossible to accurately find that number for each of those categories. Fortunately, we don’t have to.

The ONLY variables you need to pay attention to are:

• How many calories EXACTLY are you eating every day

• Has your weight gone up or down, and by EXACTLY how much.

  • For this, I like to track my weekly weight changes, while recording my weight at the same time every morning for consistency.

If you eat exactly 2000 calories per day, and lose exactly 1.0 lb over the course of a week, that means your total number of calories burned over the course of the day is about 2500. With this value obtained, you can now modify your caloric intake to mathematically understand the number of calories you want to eat for your specific goals!

Macros vs Micros

You will often hear about people “tracking their macros” when it comes to weight loss strategy. This refers to recording the number of Macronutrients (Proteins, Carbohydrates, Fats, and Alcohols) they eat throughout the day. For context:

• 1g of protein = 4 calories

• 1g of carbohydrates = 4 calories

• 1g of fats = 9 calories

• 1g of alcohol = 7 calories

In order to know how many calories you’ve consumed over the course of the day, you can look at nutrition labels or recipes to know how many of each micronutrient you’ve consumed, OR you can use a food-tracker app (like MyFitnessPal) to track the foods, and that will tell you your breakdown of macronutrients automatically! As mentioned above, these macronutrients have different impacts on the Thermic Effect of Food (TEF), and can therefore also create improved caloric expenditure when optimized. For example, If two identical people, with identical genetics and metabolic conditions, with the same BMR, ate the same total number of calories, but one of them had more protein and the other had more carbohydrates, the person who ate more protein would end the day with higher caloric expenditure than the carb enjoyer.

The recommended amount of each macronutrient a person should consume (per the FDA’s “Acceptable Macronutrient Distribution Ranges”) are as follows.

• Protein should make up 10-35% of your total daily caloric intake

• Carbohydrates should make up 45-65% of your total daily caloric intake

• Fats should make up 20-35% of your total daily caloric intake

Micronutrients are all of the vitamins and minerals your body needs to perform its normal functions and keep you healthy. These are EXTREMELY important, and should be given the same level of attention as macronutrient intake (if not more), however since they do not contain any calories, they do not factor into the mathematics of this article.

That’s it! The mathematics of weight loss and gain simply comes down to caloric intake vs caloric expenditure. In future Posts, I’ll discuss ways of increasing caloric output and decreasing caloric intake, so that you can reach those summer goals, keep those new years resolutions, and get a little bit healthier every day!