That Magic Number 3,500

One of the most cherished “facts” in the obesity field is that 3,500 calories equal one pound of body weight, and consequently, to lose a pound a week, a person has to cut their intake by 500 calories per day. But how did the experts come up with this formulation? What makes them so sure?

In order for this to be accepted, says obesity researcher Dr. Zoe Harcombe, Ph.D.,

There needs to be overwhelming, irrefutable and consistent evidence that each and every time a deficit of 3,500 calories is created, one pound of fat is lost.

She decided to look into that, and went through a hilariously lengthy process of asking various bureaus and agencies where the figure came from. Here is what she ended up with:

The organisations approached have been helpful and accessible, but none is able to explain where the 3,500 comes from, let alone to provide evidence of its validity.

Her solution would be to require that proof of the formula be furnished, and proof not only that it works, but that it works across the board. Or else announce that it is inaccurate, and move on. Why? Because…

We need to tell people that there is no formula when it comes to weight loss and we have been wrong in giving people the hope that starvation will lead to the loss of 104 pounds each and every year, in fat alone.

Of course there was a lot of pushback. The page’s comments section is bursting with arguments telling Harcombe how wrong she is. Anyone interested in the topic can find plenty there to cogitate on.

When researching weight loss myths, journalist Liz Neporent spoke with Diana Thomas, director of the Center for Quantitative Obesity Research, about the generally accepted idea that a person has to burn (or not consume) 3,500 calories to lose one pound of body weight. Thomas said,

Clicking off 3,500 calories to lose a pound may be close enough to the truth for the first 10 to 12 days of a diet as you lose water weight, but when the body weight drops you carry less mass and start to burn fewer calories for the same activities. After a period of time, you stop losing weight even if you continue to cut back by the same amount.

So, in that sense, a calorie is not a calorie. And belief in that formula causes psychological devastation to aspiring weight losers. A more recent exploration of the 3,500-calories-per-pound theory is offered by journalist Amby Burfoot, who says….

[…] the body is an organic whole, and has many reactions to changes in calories, carbohydrates, fats, proteins, metabolism, exercise, hydration, and hormones.

When you’re making a lifestyle change through diet, almost all these interrelated events conspire to lower your daily metabolic rate through a process known as “metabolic adaptation.” As a result, a daily deficit of 500 calories produces slightly less effect on each subsequent day. The difference isn’t big at first, but grows substantially with longer periods of time, producing just 50 percent of the expected weight loss over 12 months.

Burfoot also answers the eternal question: What is the optimal weight loss program? Turns out, it’s “the one you can adhere to over the long term.”

Your responses and feedback are welcome!

Source: “The Calorie Theory — prove it or lose it,”, 06/08/14
Source: “6 Weight Loss Myths Debunked,”, 07/02/13
Source: “How Many Calories Are in a Pound? Well, It’s Complicated,”, 06/10/20
Image by goblinbox/CC BY 2.0

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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