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December 23, 2022

The Myths About Calories In – Calories Out: You Will Be Shocked

calories inWeight loss is more complicated than simply being a mathematical equation. We’ve all heard that there are 3,500 calories in a pound, and that if you want to lose one pound a week you need to create a calorie deficit of 500 calories a day either by eating fewer calories or burning more calories through exercise, or some combination of the two.  This recommendation is based on the calories in – calories out concept as if losing weight is purely a mathematical endeavor.

But does calories in – calories out really work?  Well, if it did there would be fewer overweight people in this country than what we have, because nearly everyone who has ever attempted to lose weight has restricted their calorie consumption, and some have even tried to burn more calories.  Some weight loss is possible initially, but over 90% eventually regain the weight.

Why Calories In – Calories Out Doesn’t Work

Certainly if you eat more calories than you burn you will gain weight and you must create a calorie deficit to lose weight but the concept doesn’t always work. Here’s why. There are three reasons why calories in – calories out doesn’t always work when it comes to losing weight.

You Cannot Accurately Measure Calories Consumed and Calories Burned. Reality Trumps Theory.

First, there’s a practical problem. It’s not possible to accurately determine how many calories you consume each day, and how many calories you truly actually burn each day. Do you really know how many calories you eat in a day and how many you burn? If you don’t then how can you determine if you are creating a calorie deficit?

You don’t have to be off much to realize the limit of making weight loss a simple mathematical equation.  If you consume 10 calories more each day than you calculate, and you burn 10 fewer calories each day than you calculate, you are off 20 calories a day.  Multiple that by 365 days and you are off 7,300 calories, or nearly 2 pounds. Over one decade of life, say from 40 to 50 you will have been off the equivalent of 20 pounds. How’s that for a weight loss plan?

In theory calories in – calories out makes sense, but not in practice.

Calories Consumed and Calories Burned Are Dependent Variables – One Affects the Other

Secondly, how many calories you consume and how many calories you burn are not independent variables. They are dependent variables. The minute you try to change one the other one changes off-setting some of what you were hoping to achieve.  For instance, if you restrict you caloric intake each day eventually your metabolism slows down limiting the number of calories burned.

The body senses its being short changed calories so it conserves energy, therefore conserving calories by reducing metabolism. This puts you in a situation of having to restrict calories even further to create that 500 calorie a day deficit.  Conversely, if you start to exercise or if you already exercise and kick it up a notch you will stimulate a greater appetite and start to consume more calories.

Try these experiments on yourself.  Keep your exercise program the same, but reduce your calorie intake.  You will find that you will struggle with your exercise program, or find that you’re less active during other parts of the day from a lack of energy.  Then, keep your calorie intake the same and increase your activity level.  You will find that you are more hungry. You might be able to resist at first, but sooner or later you will increase your intake of calories.

But, burning more calories makes it easier to create a calorie deficit. The real reason to exercise for weight loss is to bring about hormonal effects that persist long after the exercise is over enabling you to burn more calories while at rest.

When it comes to consuming and burning calories, it’s difficult to change one without changing the other.

Not All Calories Are the Same

Thirdly, not all calories are the same.  The source of the calories is important. The source of the calories (fat, protein, carbohydrate) and the glycemic index of the carbohydrates greatly influence the secretion of hormones which determine if calories are stored as fat or are burned for energy.  See Not All Calories the Same When it Comes to Weight Loss.

Fewer calories are burned when a low-fat diet is consumed (another name for low-fat diet is a high carbohydrate diet) compared to low-glycemic diets and very low carbohydrates diets with more emphasis on protein. High glycemic foods and diets that are high in carbohydrate produce more insulin which is a fattening hormone and prevents the burning of calories from fat stores.

A calorie is not a calorie; some are better than others.

Increase your activity level, consume a balanced low-glycemic diet, optimize your hormones, and you will increase the odds greatly that you will achieve a healthy weight that you can maintain as you age. In the end, this the best and safest way to lose weight.

Article updated 12/23/22.  Originally published on 8/11/12.


Good Calories, Bad Calories: by Gary Taubes

Why We Get Fat: And What To Do About Itby Gary Taubes

See related articles.

“High Intensity Interval Training: Short and Sweet”

“Low Glycemic Foods”

“Achieve Weight Loss With These Hormones”


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Dr. Joe Jacko

Dr. Joe is board certified in internal medicine and sports medicine with additional training in hormone replacement therapy and regenerative medicine. He has trained or practiced at leading institutions including the Hughston Clinic, Cooper Clinic, Steadman-Hawkins Clinic of the Carolinas, and Cenegenics. He currently practices in Columbus, Ohio at Grandview Primary Care. Read more about Dr. Joe Jacko

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