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Obesity Myth #1: The 3,500 Calorie Rule


Yesterday, the New England Journal of Medicine published a paper that addresses common myths, presumptions, and facts about obesity.

As the authors note in their introduction,

“Passionate interests, the human tendency to seek explanations for observed phenomena, and everyday experience appear to contribute to strong convictions about obesity, despite the absence of supporting data. When the public, mass media, government agencies, and even academic scientists espouse unsupported beliefs, the result may be ineffective policy, unhelpful or unsafe clinical and public health recommendations, and an unproductive allocation of resources.”

In this paper, the authors address seven myths, six presumptions and nine facts, which I hope to address individually in upcoming posts.

The first myth addressed in the paper is the common misconception that a continuous daily excess of a few calories per day will result in continuous weight gain.

This myth (also referred to as the 3,500 Calorie Rule) is often presented in a way that numerically adds up the number of excess calories you may be eating per day (say 100) and translates this into weight gain by simply equating 3,500 extra calories to one pound weight gain.

Thus, even academic publications often suggest that a 100 extra calories per day over a year (say about 350 days) would result in 35,000 extra calories or a ten pound weight gain.

You will also often find the converse, where simply burning an extra 100 calories a day is equated to losing 10 lbs.

This, as explained in the paper is a myth because such simplistic calculations do not take into account the physiological mechanisms that result in compensatory energy conservation or expenditure, thereby limiting changes in body weight.

Thus, although a pound of body fat may well represent about 3,500 calories (which it roughly does), an extra pound of body fat is not simply the numerical result of ingesting an extra 100 calories per day for 35 days.

Nor does a daily caloric deficit of 500 calories result in a weight loss of one pound a week, week after week after week, till you finally disappear.

As I have previously explained, significant and ongoing weight gain or weight loss actually requires a substantially greater level of daily caloric excess or restriction that may have to incrementally increase over time to sustain continued gain or loss.

It is therefore safe to ignore statements that are commonly found both in academic publications and in popular media presenting simplistic statements like, “an extra potato chip a day over 20 years can lead to a 50 lb weight gain or an extra can of pop a day can lead to a 20 lb weight gain in one year”.

In reality, ingesting 3,500 extra calories does not simply translate into an extra pound of body fat – nor does burning 3.500 extra calories result in a pound of weight loss.

Or, as I say in my talks, “This is not physics, this is physiology!”

For a detailed discussion of how many calories it actually takes to lose or gain weight click here.

AMS
Edmonton, AB

11 Comments

  1. I am always amazed that people think that metabolizing 3,500 calories is the same for everyone, and totally the result of their behavior.

    I might be comparing notes on my Buick with another Buick owner of the same model and year. If I share that my gas milage is 3 miles per gallon better than hers, she doesn’t immediately jump to the conclusion that my driving habits are superior to hers. She would explore that possibility, but also look at a broad range of other potential causes — clogged mechanisms, potentially worn-out parts, etc. And, the thing is, a Buick is a limited machine by comparison to the human body. How efficiently or inefficiently the human body processes its fuel depends on mechanics PLUS dozens, hundreds, maybe thousands of additional genetic, environmental and hormonal variables! And yet, two women, same age, different weight will leap to the assumption that the fat one is lazy and gluttonous. If she would simply cut 500 calories a day from her diet or burn an extra 500 with exercise, she’d soon be trim for life. Lah-de-dah.

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  2. Incidentally, as an addendum to this myth, it also implies that the commonly heard advice that, “Small changes, over time, can lead to big changes in body weight”, are essentially nonsense. Losing (or gaining) a large amount of weight requires substantial, persistent and often incremental changes in caloric intake or expenditure to sustain. Thus, for e.g. even completely giving up the one teaspoon of sugar in my daily cup of tea, although adding up to 1000s of fewer calories over the years, may do almost nothing in terms of reducing my body weight. But, if I drink 10 cups of tea each day, and cut out sugar in all of them, thereby saving hundreds of calories per day, I will definitely expect to see some weight loss. I guess what you consider a “small” change is a matter of perspective.

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  3. The study of obesity is, for the first time, exploding with new information and new treatments. “Myths, Presumptions, and Facts About Obesity” is another game changer. I’m sharing your post with me readers and patients as headline news.

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  4. bravo, and well-expressed, Dr. S!

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  5. Yes, many of the authors of the paper have ties to food, pharmaceutical and commercial weight loss companies – this neither validates nor discounts the paper for what it is. I tend to worry more about people who have no conflicts to declare – it is usually these “holier-than-thou” ideologists that I tend to mistrust – it is the ‘hidden agendas’ of these folks that I worry about. Let him, who truly has no ‘conflict’ cast the first stone.

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  6. I don’t buy the first myth. I do believe that we don’t eat an exact amount overage, but if one does develop a new habit (say, getting a cola for the ride home from the brand new vending machine outside work or school), there is a good chance the body won’t change physiologically, nor that the person will have enough energy suddenly to burn those extra 100 to 180 calories.

    We see so many people at average weights becoming obese by their thirties that aren’t suddenly overeating one day to become obese, and the weight gain seems gradual. To suggest that the minimal over-consumption of calories is only a myth is to wreck the potential for stopping potential roads to obesity and metabolic syndrome before people get there.

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  7. Great post Arya!

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  8. It is very naive to dismiss the conflict of interest of authors of a study, especially with such strong ties as being board members of drug , food companies and food lobby organizations. There are many people in the nutrition and health field with no business/industry affiliation and to worry more about these, as you put it ‘holier than thou ideologists’ is to ignore the reality of bias in studies by people who represent industries that would profit from their findings.

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  9. Yes, the calorie system is not accurate in many ways, as explained in this post. Still, since I’ve been watching calories, the weight is going down faster than ever. It still is a good tool to use, at least for me.

    :-) Marion

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  10. I learned the hard way, a long time ago, that you can throw all the best metabolic research at the public, but if it doesn’t fit their internalized moral paradigms, it’s completely useless. Thank you for this post and for stressing these issues. If enough experts bring up and stress these issues on a regular basis, they will seep very slowly into the public consciousness, and will take root within a few generations.

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