The Calories In/Calories Out Myth

The idea that the body works on a simple calories in/calories out (ci/co) model is one of the most pervasive myths that I hear. This particular myth is extremely damning to us fats since the idea is that:

If  you just eat less, exercise more  and create a caloric deficit (ie:  do not give your body the amount of fuel it requires to function), you will lose weight and therefore be more healthy. If you fail to lose weight, it just means that you lack the will-power to create a caloric deficit over a long enough period of time.

I’ve already talked about the conflation of the concepts of weight and health, so today let’s just talk calories in and out.

It sounds really logical, especially if you don’t understand how the human body actually works.

First, it turns out that accurately calculating the calories out side of the equation is at best an awfully indirect science producing questionable results.

The Basal Metabolic Rate (BMR) formula is one of the most popular used to determine how many calories we burn at rest. But  the formula doesn’t account for muscle mass, which utilizes more calories than other body tissue at rest.  Except that there is controversy about just how many calories a pound of muscle utilizes – some reputable scientists say that it burns 35, some say 10.  Also, most methods used to measure muscle mass are fairly imprecise, or really expensive, so very few people have access to a correct measurement even if we could use that number to get an accurate BMR, which we can’t.

Besides which, a BMR-type calculation would be reasonable  if we were a lawnmower.  We can calculate the fuel needs of a lawnmower and then have a reasonable expectation of how much grass it can mow and what will happen when the fuel runs out.

Ready for a blinding flash of the obvious?  Our bodies are not lawnmowers.  The way that we utilize fuel (calories) and what happens when we run out is vastly different and extremely individualized and affected by all kinds of things including:

What concerns me even more is that semi-starvation is advocated based on the idea (really, the desperate hope) that a starved body will burn excess fat for fuel. That’s not necessarily the case.  Your body is really good at surviving.  It is not so good at fitting into a cultural ideal of beauty.  The body doesn’t think of calories as evil things that take it farther from an arbitrary standard of beauty, it thinks of calories as fuel to do its job. When you give your body less calories than it needs to perform its basic function it does not think “look how disciplined you are to underfeed me so that we can become smaller”.  It thinks “Holy shit, I’m starving.  I have to do something!”

Let’s go back to the lawnmower example:

If I give my lawnmower half of the gas it needs to cut my lawn, it will simply stop working half-way through. If tomorrow I only give it 1/2 of the fuel it needs, only 50% of my lawn will get cut. My lawnmower will never adapt to use less fuel,  it just stops working.

If I give my body half the fuel that it needs just to lay in bed all day, and proceed to run on a treadmill it doesn’t stop  – it adapts. My body can’t imagine a scenario in which it needs food, there is food, but I’m intentionally starving it, so it interprets this situation as  “I’m starving, there is no food, and I have to run away from something”.

If I continue to underfeed my body while making physical demands it will likely drop weight at first while adapting to function on fewer calories, even if that means performing those functions (you know: thinking, breathing, heartbeat, walking etc) non-optimally.  If I continue underfeeding for the long-term I will experience negative impacts (see below).  If I stop underfeeding my body there is a good chance that my body will maintain it’s adapted lower level, at least for a while, while possibly also resetting my natural set point to a higher weight permanently while storing anything it can as fat.  My body is trying to help me out – what it has learned is that I live in an environment where sometimes starvation happens at the same time that massive physical labor is required, so it’s storing up fuel for the next starvation/high physical activity period. If I continue to do this over time (as in the case of yo-yo dieting), then the damage to my metabolic rate, my natural set point, and my body’s functions can be severe.

And that doesn’t even touch the psychological toll that underfeeding your body takes on you. In the Minnesota Semi-Starvation Study participants who were restricted to 1,560 calories per day for 12 weeks experienced depression (up to and including serious self-mutilation), hysteria, marked food preoccupation, disordered eating patterns,  guilt about eating, decline is physiological processes, concentration, comprehension and judgment, and a 40% drop in BMR.  For many the disordered eating continued for 5 months or more after the study was concluded.

So while semi-starvation (also known as dieting) seems like a reasonable weight loss technique if you believe in a ci/co equation, I have to judge it on three standards:

Validity of Methodology

Fail.  The fact that I can’t accurately calculate how many calories my body will expend or predict how my body will respond to prolonged starvation makes this methodology invalid.

Probability of Success

Fail.  The use of caloric deficit has a success rate of 5% over 5 years – that’s within the margin of error for most studies and is an unacceptable success rate for me.

Acceptability of Risks

Fail.  I’m risking my current excellent physical and psychological health for a chance at a smaller body.  That, for me, is an unacceptable risk.

Which is why I’m sticking to my plan of engaging in healthy behaviors, giving my body the fuel it needs, and letting it determine what size it’s going to be.

Literature Review

There is not a single study in which the majority of people maintained weight loss long term, and there is definitely not a study wherein the majority of people maintained a BMI-changing amount of weight loss long term. There are plenty of studies that show that ci/co weight loss almost never works











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Published in: on March 6, 2011 at 8:27 pm  Comments (37)  

37 CommentsLeave a comment

  1. I’ve always thought the calories in/calories out thing was good science! I never thought to consider the other factors. I’ve been really curious about that new Jenny Craig system that measures metabolic rate for weight loss.

    I was just in the kitchen counting calories…

    I have a lot to learn…

    THanks for this blog, Ragen!
    xo Susie

    • Hi Susie,

      Yup, this myth has become a part of our cultural fabric, but it’s still a myth. I Googled the Jenny Craig thing. I appears to use a monitor that utilizes some form of the BMR formula to calculate how many calories you’ve burned in a day. It’s subject to all of the inaccuracies I mentioned above with a bonus side of the possibility of being triggering for someone predisposed to eating disorders, and putting you on a diet where you eat only highly processed microwaved food that provides only 8 grams of fiber a day (25g is typically recommended), has a ton of sugar, and according to a nutritionist “The meals are quite low in calories (fewer than 300 calories for most). Without much fat or fiber to keep your blood-sugar levels steady and your appetite in check, you’ll be chewing your arm off 90 minutes after every meal.”

      Sorry to be the bearer of bad news!


  2. Love how you share information and debunk myths so accessibly! Thanks for this!

    • Thanks Anna! I’m such a fan of your work, I’m really glad that you like mine!

  3. I have never dieted successfully for more than a few days. That’s actually got me into therapy for my ED. Since letting go of all restrictions I have gained about 20 pounds. I now eat candy and other sweets almost daily and it works for me. It is so much better than restricting. I still have problems with body image but I am getting better. I am the top end of straight sizes and fear I will continue to gain weight and grow out of them. On the flip side, I have been working with a trainer for the last 18 months and I have never been fitter and I am more comfortable with my own body than ever.

    I am still struggling with my own attitudes about the cultural idea.

    Thanks for listening.

    • Hi JennyRose,

      A lot of people have stories like yours and I really commend you getting help for ED and working through this process. I’m happy that you are fit and more comfortable with your body. Keep rocking!

  4. You know, I think I like the “the body isn’t a lawnmower” metaphor better than the “the body isn’t a bunsen burner” metaphor.

    I’ve had troubles with the idea of calories in/calories out thing for a long time now. Especially when I was actively trying to lose weight and actually ended up gaining instead, even when holding firm to the whole ci/co idea.

    The human body (and really all bodies) are far more complex than we give them credit for. I think sometimes we try so hard to over-simplify how our bodies work, and we end up getting these ideas that don’t actually work but we cling to them as if our lives depend on them.

    Thank you, Ragen!

    • Thanks Karen,

      I think that you are so right about bodies being much more complex that we give them credit for. I think it tends to develop from the “one size fits all” (forgive the pun) approach to health . It’s really frustrating and I think it’s doing everyone a disservice.


  5. Wonderful post, thank you.

    • Thank you! Glad that you liked it.


  6. I have further to go than I thought. Throughout this post I kept thinking to myself, kind of panicky: Then how can I lose weight in a healthy way? I have to answer myself: Losing weight is not a healthy goal for me. Though I am a nerd, I never really thought of the whole notion of calories as being flawed. Obviously it is, and it should have been obvious to me all along.

    I have begun to put higher quality food in my body–slowly adding whole grains, fruits and veggies without cutting out anything I normally eat. I have no idea if my weight has changed at all, because I haven’t stepped on a scale in several weeks, but I can tell that my health has improved. This is more encouraging to me than any arbitrary number.

    • Hi Skyfire,

      It’s no surprise that this one stuck with you – it is an incredibly pervasive myth- repeated and worked into the fabric of our culture. (I just heard it used in the contest of saving money: “If you live on less than you earn, you’ll save money. Just like you’ll lose weight if you eat less.” Doh!

      I’m really glad that you’ve found a path that is helping your health improve. Keep kicking ass!


  7. I really like this post. I am currently giving intuitive eating a go but it is really hard to stop trying to lose weight. I just want to be able to eat whatever I want at that moment and then move on. Dieting sucks.

    • Hi Stacey,

      Glad that you liked the post. I know that when I started intuitive eating I really struggled with letting go of my former dieting habits. Good luck, let me know if I can help!


  8. It took me a REALLY LONG TIME to come to terms with this when I was essentially starving myself to death. Walking that borderline between dieting and anorexia, I ate 1000 calories a day and did an hour of cardio plus weights five times a week. NOT HEALTHY. Eventually, I figured out that I was doing some serious harm to my body, and I read up on the calories in/calories out idea. Like you, I figured out it was bullshit. And so I ate some ice cream and backed off my gym time.

    Thanks for writing all this out in an easy to digest format. I can only hope that other people find this and get some help from it.

  9. When someone comes at me with the ci/co thing, I look at them with my “bad science” face and say, “That’s true. It’s also tautological, useless, and irrelevant. Because unless you are living in a very expensive lab where they weigh the very air you breathe, you cannot know how many energy you take in or how much you use.”

    The only healthy way to lose weight, IMO, is if you gained it as a result of not being healthy and you are in better health now.

  10. One thing I think is a constant failure of those who tout the calories in/calories out line of thinking is the inability to accept that a living organism is not the same as a machine.

    Bodies are not machines. They are not created by engineering and science. They are beings grown organically by nature, specifically designed as they live and grow for the environments they inhabit. As those environments change, the living organism changes with it to adapt.

    For all the “it’s a simple concept” talk of ci/co, there is an even simpler concept that so many fail to grasp.

    • In fact, even when it comes to engineering, humans are noticably bad at handling even simple feedback loops that include a time delay. Nested feedback loops with time delays will spin out of control if someone so much as looks at a lever sideways. However, “nested feedback loop with time delays” describes many natural systems perfectly.

  11. There’s also the fact that when losing weight, your body loses muscle. Strength training while losing weight can reduce the amount of muscle lost (not sure about cardio), but you WILL lose muscle. Your body’s not like, “I want to have a bikini body and show off my six-pack!” Your body’s thinking, “Hey, I better jettison this metabolically expensive muscle and hoard my energy in this fat!”

  12. Thank you for explaining this in such depth. I had heard that the CI/CO theory was incorrect, but most people just said that it was incorrect, I never saw it truly explained. You did a great job here.

  13. Writing an article that contains only one cherry picked reference to a study from 1950 is in itself bad science.

    • Hi Taylor,

      Sometimes people mistake this blog for a scientific article and it seems like you might be making that mistake. The people who tell us the calories in/calories out myth are often doctors and news sources. I am neither. My goal wasn’t to write a scientific article, it was to give people an opportunity to rethink a commonly stated concept that I think is erroneous. The amount of research I do for a blog is always massive. How much I choose to cite depends on a number of factors including how easily the info is available online (often I’m reading things in journals etc.), how much time I have to complete the blog (I’m a corporate CEO and dance professional so I don’t have a ton of free time) and how much I feel like citing sources. Hope that clarifies things!


  14. Well of course establishing a calorie deficit is not the only thing to attend to. That said, ALL of my obese trainees presented a sedentary lifestyle and calorie intake far above BMR. No exceptions. And all of my obese trainees who are steadily shedding fat have establshed calorie deficits and have increased general activity. No exceptions. Either I just hit the lottery or you’re making it too complicated.

    • Well, BMR is “if you’re staying in bed all day”, so even if they’re sedentary, if they’re moving around to do normal activity such as housework, I would think that anyone with a stable weight WOULD have a calorie intake far above BMR.

      If people come to you because they are inactive and not sure how to start being active, you don’t exactly have a representative sample. Here’s another non-representative sample that showed 39% of overweight and obese people exercised regularly, and another 29% had been exercising for 6 months. But I guess any fat person who claims to be exercising is lying? Are all Ragen’s dance videos just computer-generated hoaxes?

      And all of my obese trainees who are steadily shedding fat have establshed calorie deficits and have increased general activity. This doesn’t prove the converse–that reducing intake to what “should” be a calorie deficit and increasing general activity will without exception cause people to steadily shed fat.

      And note that all your trainees (I’m guessing you’re a personal trainer?) are currently active, not sedentary, no exceptions.

  15. Wow! Great post!

    I’ve added your blog to my bookmarks after noticing that all the interesting links I click on bring me to it.

    I have to admit that until recently, I believed this myth too. I went on several diets where calories were restricted, only to be disappointed when the scale didn’t show me the results I wanted. When I stopped the diet, I would gain back what little I had lost and then some. For years I convinced myself that I was doing something wrong, and that maybe I was unintentionally sabotaging my weight loss goals. None of it mattered. According to BMI, I was obese and no amount of calorie restrictions helped me shed those pounds.

    Last year, I joined a gym. I went 3 times a week for 2 hour workouts. I also watched what I ate (not dieting, just good things in moderation). I did lose some weight and kept it off for months. I’m nowhere near my goal weight though. What I am interested is if “calories in/calories out” doesn’t work by itself, then what does? It makes some sense that CI/CO would be a part of the whole equation (where other factors should also be considered), but I have experienced first hand that it is not THE solution. I’m not interested in the short term fix (and subsequent weight yo-yo’ing) that happens with all the popular diets that use the CI/CO model.

    I am much healthier now than I was before. My eating habits have significantly improved and I’ve noticed that that alone helped other areas in my life (like sleep and concentration). I know this may not be everyone’s experience, but I do want to lose weight. I want to be healthy and fit (and fit into my clothes!). I know I still have some self-image issues to work out, but who doesn’t? I applaud anyone who is happy in their own bodies, whatever its size. It’s not an easy thing to do in our “skinny is ideal” society.

    Thanks again for the great blog Ragen!

    • Hi Nathalie,

      Thanks for the comment. As far as what is the way to lose weight, I don’t know. I do know that every method that has been scientifically tested has had only a 5% success rate so nothing that we’ve tried so far works for long term weight loss. As far as being healthy and fit and fitting into your clothes, I’m not sure that I can help you. it’s sounds like you’ve found a path that’s lead you to health and fitness. My solution to fitting into my clothes has always been buy clothes that fit the body I have now. That’s not to say I don’t respect your desire to lose weight, I absolutely do, I just don’t have any way to help you with that part of your journey.



  16. Great post, Ragen! I can’t seem to convince even my alternative health care professionals that, for me, cutting calories just makes my metabolism drop. I can lose about five pounds of water, at most, but even if I stay on the diet it comes back within a few weeks. As for exercise “where you get you heart rate up for at least 20 minutes,” that may make some people’s metabolism go up, but with me, I think what happens is that my body interprets that as extreme stress, and an indication that it has to conserve as much fat as possible. This was true even when I was in my teens and ’20’s (when I tried extreme dieting that probably permanently slowed my already sluggish metabolism). Remember the protein sparing fast? I got sick on it very quickly – no energy and extremely tired no matter how much sleep I got – but lost no weight! My body seems to refuse to burn its own fat for energy in the absence of enough food. I am the only person who gained weight and inches after four weeks of low cal dieting and nearly daily aerobic and weight-bearing workouts at Women’s Workout World in the 90’s! As someone said on another blog, why is it so easy for so many people to believe that someone can consume enormous amounts of food and stay thin, but they can’t believe that others can consume much smaller amounts of food and not lose weight? I do not know that this is a universal phenomenon, but it is true for some people, just as some can eat in quantity and stay thin.

    • YES.
      Same with exercising being part of the equation.
      My friend who recently received her certification (certification, or training or badge, whatever) as a personal trainer will admit that she knows people who are skinny but unhealthy in their lifestyle, but just cannot seem to see the possibility that the converse could be true.


    Wonderful, succinct explanation of something that’s always frustrated me in the past. (Also, your description makes me feel really happy about my body’s adaptability and tenacity! We’re pretty tough creatures, as it turns out!)

  18. I suspect that a body which can maintain a constant temperature in various conditions can also modulate the amount of food energy it uses. Ii would be surprising if it didn’t.

  19. Oops, this commenter is a jackass. To read this comment you’ll have to check out my hatemail page There you can read my hatemail, my responses to it, and see how I use comments like this to fund my work around self-esteem, body image, and Health at Every Size.


  20. Thank you for pointing this out. I hate that myth, though it affects me for the opposite reason to you.

    I’m about 5’7 and 53kgs and I just don’t put weight on. People’s usual response is ‘You don’t eat enough!’ No matter how much I am eating it’s always magically not enough.

    I once tried forcing myself to eat once per hour…once per hour. Result? I lost 2 more kilograms and suffered nonstop overheating. I just don’t use that fuel to gain weight, it gets burned as heat.

    Try telling anyone that and they’ll say ‘Eat MORE once per hour! Oh, you puked? Well, eat anyway!’

    Thank you for pointing this out. I love your writing. Please keep being awesome.

    • Hi Kaliane,

      I’m so sorry that this happens to you, and I’m glad that you are finding a path to health that works for you. Thanks for pointing out that it happens to all sizes, I’m so sorry if you felt left out, I absolutely should have pointed that out as well. Thank you for your kind words about my writing.


  21. WOW. I just came across this blog this morning. I believe you are right on the money. I couldn’t agree with you more. I am glad you had to courage to post this since it goes against what “fitness” and “nutrition” “experts” tell us. Yesterday on CNN a fitness “expert”, I forgot his name, said that calories in/calories out is a MYTH and deficitis are never good. We need to fuel our bodies not starve them. I too am “obese” now but I am healthy on the inside I used to weigh 135 from age 14 thru 30. I was in the Navy, I did not count calories, I ate healthy most of the time. I started gaining weight in 2007 due to what I consider a change in the way my body metabolized food as a result of a medication I was taking.
    Long story Short, I am so glad that you take the time to understand how the human body works instead of just buying what “experts” are selling

  22. Hi Ragen,
    I know this is an old post but I have to ask: do you have any idea how to restore your metabolism after a moderate period (3-4 months) of low calorie intake (sub1200)?

  23. Super glad I found this in the top page of my google search about cal in/out. Keep preaching the truth. It’s good to know it’s out there – people need it so much.

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