The Science of Fat-Loss: Why a Calorie Isn't Always a Calorie


Calorie counting can work, but it’s often based on pseudo-science.

I’ve examined before how people can lose 20+ lbs. of bodyfat — or gain 34 lbs. of lean mass — within four weeks, replete with measurements and photographs, but there is still a chorus: “That’s impossible! You’d need to have a 4,000-calorie daily deficit” or “That’s impossible! You’d need to consume 20,000 calories per day!”

Nonsense. Thermodynamics isn’t so simple, and you can accelerate your body optimization results by understanding the real science…

I’ve invited Dr. Michael Eades, one of my favorite bariatric (obesity treatment) doctors in the US and the first to introduce insulin resistance to the mainstream, to explain the facts vs. disinformation. He is author of one of the few research-driven weight-loss books I recommend, Protein Power.

Take it away, Dr. Eades…

Dr. Eades:

I’ve taken some heat for my writing that weight loss or weight gain involves more than a simple accounting for calories.

The entirety of mainstream medicine and nutrition believe that calories are the only thing that counts and that a low-carb diet is nothing more than a clever way to get people to cut calories. Weight loss on low-carb diets, so they say, occurs only because subjects following low-carb diets reduce their caloric intake. A calorie is a calorie is a calorie they say. But is it?

I could argue that this idea isn’t necessarily true because of a number of recent studies that have shown that subjects following low-carb diets actually lose more weight than their counterparts on low-fat, high-carb diets despite the fact that the low-carbers consumed considerably more calories. But instead of going through these modern day studies, let’s go back and look at a couple of earlier famous studies to see what we can learn.


In 1944 Ancel Keys, Ph.D., decided to undertake a long-term study of starvation. It was apparent that WWII was going to be over soon and that much of Europe was starving. Although word of the mass starvation in concentration camps was just starting to filter out into the world, it was well known the Europeans, especially Eastern European, were not getting enough food. Keys wanted to do a study of starvation to see what really happened during the process so that at war’s end the victors would have a better idea of how to deal with the starving masses they were sure to encounter.

Key’s recruited 36 young male volunteers from the cadre of the conscientious objectors. These were healthy, normal weight men, most of whom were working for the Civilian Public Service (CPS), an entity created to provide jobs of national importance for conscientious objectors. The men responded to brochures and bulletins distributed in the various CPS barracks showing a photo of three French toddlers staring at empty bowls over the question: WILL YOU STARVE SO THAT THEY WILL BE BETTER FED?

The subjects came to the University of Minnesota where they were housed in the cavernous area underneath the football stadium for the course of the study. They were basically kept under lock and key for the study so that Keys and his colleagues could ensure compliance. At the start of the experiment the men were fed sumptuously for the first 12 weeks.

A full-time cook, two assistants and a dietitian monitored the food intake to the smallest fraction. According to The Great Starvation Experiment**, an excellent book about this famous study, during this lead-in phase the men ate well. A typical days food would include

a typical lunch… [that] consisted of fricasseed lamb with gravy, peas, and a carrot and raisin salad. For dinner…the men ate roast beef with gravy, whipped potatoes, tomato salad, and ice cream for dessert.

Although the three meals per day the men received added up to around 3,200 calories, which they were told approximated the normal American diet, the men said that they had never eaten better in their lives.

On day one of the starvation portion of the study, February 12, 1945, the rations were cut substantially.

The group shifted overnight from the three relatively generous meals of the control period to only two Spartan meals per day, a breakfast at 8:30 AM and supper at 5:00 PM.

The meals were designed to approximate the food available in European famine areas, with a heavy emphasis on potatoes, cabbage, and whole wheat bread. Meat was provided in quantities so small that most men would swear in later years that none was included at all.

One of the three dinners included the following:


185 grams of bean-and pea soup (made with 5 grams dried peas, 16 grams of dried beans, and 15 grams fresh ham)

255 grams macaroni and cheese (made with 130 grams wet macaroni, 12 grams lard, 108 grams skim milk, 2 grams flour, and 35 grams American cheese)

40 grams rutabagas

100 grams steamed potatoes

100 grams lettuce salad (80 grams lettuce, 10 grams vinegar, 10 grams sugar)

The relatively bulky 255 grams of macaroni made that particular meal an anticipated favorite among the volunteers. The wet macaroni served was roughly the amount required to fill a coffee mug about three-quarters full.

Over the twenty-four week starvation part of the study, the subjects not only lost a considerable percentage of their body weights, but suffered a number of problems as well. As the time wore on the men thought ceaselessly about food, they became lethargic, they were cold all the time, they became depressed, they developed bleeding disorders, their ankles became edematous, and some developed more serious psychological disorders.

Below is a photo of one of the young men in this study (the book shows multiple photographs – this one is typical of all the subjects). The first photo was taken a couple of years prior to the start of the study, the second is with about a month shy of the end of the experiment.


This young man suffered such psychological turmoil from the semi-starvation that he chopped off several fingers of his left hand a month or so after the bottom picture was taken.

The men in this study consumed macronutrients in the following amounts daily: protein 100 gm, fat 30 gm, and carbohydrate 225 gm. If you express these intakes as percentages, you come up with 25.5% protein, 17.2% fat and 57.3% carbohydrate.

Average energy intake of the subjects in the experiment: 1570 calories per day.

Now let’s look at another experiment conducted about 25 years later.


In the late 1960s John Yudkin’s group at the University of London performed a study that is most interesting in view of the Keys’ semi-starvation study. (Click here to get the complete pdf of this study)

For about 15 years Dr. Yudkin and his team had been running a weight loss clinic out of the university hospital using a low-carb dietary approach. Despite the patients’ doing well on the program, he and his staff had received the same criticisms all of us have who treat obese patients by restricting carbohydrates. In addition, because of his academic standing and long list of scientific publications, Yudkin’s peers had given him heat over the fact that his diet didn’t provide enough of all the vitamins and minerals required for health. As a consequence, he decided to do a study to see if there was any substance to their fault-finding.

He recruited 11 subjects aged 21-51 years for his study. He and his staff evaluated the regular diets of these 11 subjects over a two week period. The volunteers were then instructed on the basics of low-carb dieting as it was done in the hospital clinic and followed for two weeks on this regimen. The goal of the study was to determine the dietary intake of the essential nutrients in the low-carb diet to see if there were inadequacies.

Here were the low-carb instructions:

The instructions relating to the low carbohydrate diet were identical to those given to patients attending a hospital overweight clinic under our supervision. Essentially, the subjects were asked to take between 10 and 20 oz milk daily (about 300-600 ml), and as much meat, fish, eggs, cheese, butter, margarine, cream and leafy vegetables as they wished. The amount of carbohydrate in other food was listed in “units” with each unit consisting of 5 g carbohydrate; the subjects were told to limit these foods to not more than 10 units (or 50 g) carbohydrate daily.

As the low-carb portion of the study was progressing, Yudkin and his staff evaluated not only the intake of these subjects, but their mental status as well.

In conformity with our experience with this diet during the last 15 years, none of our subjects complained of hunger or any other ill effects; on the other hand, several volunteered statements to the effect that they had increased feeling of well-being and decreased lassitude. The average intake of calories and of protein, fat, and carbohydrate for the 11 subjects…were remarkably similar to those obtained for the six subjects of the previous study. [Yudkin had published a study in The Lancet in 1960 looking at the caloric and macronutrient intake of subjects on low-carb diets.]

Here is the chart from Yudkin’s paper showing the caloric and macronutrient changes when the subjects shifted from their regular diet to the low-carbohydrate diet.


The macronutrient consumption was 83 grams of protein, 105 grams of fat and 67 grams of carbohydrate. Putting this into percentages of overall intake, we find that diet was 21.3% protein, 60.6% fat and 17.1% carbohydrate. The energy intake was 1560 calories per day, almost exactly the same as the Keys study described above.

And, remember, these people were given all the food they wanted to eat. They weren’t forced to drop their calories to 1560 per day – they did it spontaneously because they had eaten until sated.

Here is the data in tabular form.


As you can see, the big difference is in the carbohydrate intake and fat intake. They are just about the reverse of one another in the two studies.

Both studies provided between 1500 and 1600 kcal per day, but with huge differences in outcome. In the Key’s semi-starvation study (high-carb, low-fat) the subjects starved and obsessed on food constantly. In the Yudkin study (low-carb, high-fat), the subjects, who had no restriction on the amount of food they ate, volitionally consumed the same number of calories that the semi-starvation group did, yet reported that they had “an increases feeling of well-being.” Instead of lethargy and depression reported by the Keys subjects on their low-fat, high-carb 1570 calories, those on the same number of low-carb, high-fat calories experienced “decreased lassitude.”

Both groups of subjects were consuming the same number of calories, but one group starved while the other did just fine. One group had to be locked down to ensure they didn’t eat more than their alloted 1570 calories; the other group voluntarily dropped their intake to 1560 calories and felt great. What was the difference? Subjects in both groups ate the same number of calories.

Maybe, just maybe it’s not the number of calories that makes the difference, but the composition of the calories instead.

I know that I’m not truly comparing apples to apples with the Keys and the Yudkin studies. But the Yudkin study does confirm Yudkin’s 15 years of experience before he wrote his paper and they confirm my 20 plus years of experience taking care of patients on low-carb diets. I’ve had many, many patients who have stayed on low-carb diets for much, much longer than the men in Keys’ experiment stayed on their diets of roughly the same number of calories. Most of the papers in the medical literature on low-carb diets show a spontaneous drop in caloric intake that’s about what Yudkin documented when people switch over to low-carb diets. It stands to reason that if someone had replicated Keys’ experiment using the same number of calories, but with much more fat and a lot less carbohydrate, that the outcome would have been much different.

Yet the calories would have been the same.

So, I’ll say it again. It’s not simply a matter of calories, and anyone who says it is should perhaps give the issue a little more thought.

** Gary Taubes’ book Good Calories, Bad Calories devotes a couple of pages to this semi-starvation study as well.

Enter Tim: This is just one of several topics I’d like to explore within the real-world science of body redesign — anything in particular you’d like to hear about?


[If you liked this post, please take a second to Digg and Stumble it!]

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The Art of Letting Bad Things Happen (and Weapons of Mass Distraction)

Posted on: February 25, 2008.

Watch The Tim Ferriss Experiment, the new #1-rated TV show with "the world's best human guinea pig" (Newsweek), Tim Ferriss. It's Mythbusters meets Jackass. Shot and edited by the Emmy-award winning team behind Anthony Bourdain's No Reservations and Parts Unknown. Here's the trailer.

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215 comments on “The Science of Fat-Loss: Why a Calorie Isn't Always a Calorie

  1. Tim,

    As a writer for Men’s Fitness and Men’s Health and fellow training aficionado I have to say you and Dr. Eades hit the nail on the head. There is much more at play than what people think.

    To lose fat, sometimes you have to eat fat. People have a hard time understanding that. Monounsaturated fats and certain polyunsaturates actually speed up the metabolic rate.

    The best of the fat burning bunch are the highly unsaturated omega 3s called EPA and DHA. These omega 3 fatty acids can potentially help burn fat through a variety of different mechanisms. A diet supplemented with something omega 3-rich fish oil promotes losses of body fat with simultaneous gains in lean mass.

    And the importance of protein should be neglected, either. While all macronutrients require metabolic processing for digestion, absorption, and storage or oxidation, the thermic effect of protein is roughly double that of carbohydrates and fat. Therefore, eating protein is actually thermogenic and can lead to a higher metabolic rate.

    What does this mean for the average guy? Eating a diet rich in protein and good fat (high satiety factor)and moderate in “complex carbs” usually yields the best benefit with regard to looking good naked.

    And that’s not even talking about the training aspect of caloric expenditure and the EPOC (Excess Post Exercise Oxygen Consumption) Effect.

    Keep up the good work!


  2. Nice Post! I think this is true. I have noticed many people on low carb diets drop fat like crazy and those on on low fat not so much. I myself have experimented with both, and the low carb diet seems most effective.


    Jose Castro_Frenzel


  3. Until nutrigenomics is fully realized, lowering carbs by way of starch elimination seems to be a better dietary choice for most of the population. I especially like this study where, in spite participants being fed nearly 5000kcal/day (4000kcal from fat) for 45 days and refused to gain fat:

    The research is clear: have carbs when you’ve earned them…after a workout!


    Excellent point, Skyler. Nutrient timing is another topic I hope to explore very, very soon. Thanks for the reference!



    • I just started this diet. I am on day #2. I already feel better. I take supplements and I’m wondering if that is acceptable on this diet. I take omega 3, biotin, D, and Gaba Calm. What are your thoughts on these?


  4. I meant to say “the importance of protein should NOT be neglected either.”

    From a personal training stand-point, the compliance rate is much higher with clients who are put on an eating plan where the fat is equal to or slightly higher than the carbohydrates.

    It’s easier on the stomach but it’s hard information to swallow.


  5. Great comparison! It’s certainly intriguing to see results like that.

    I remember reading about how strict Lance Armstrong was with his diet and how he weighed his food, but like you said, that’s not the whole story.


  6. Great post.

    Ever heard of Vince Gironda? He was a trainer of pro bodybuilders in the 50s & 60s. He was a strong advocate of high protein & fat, low-carb diets for losing fat while minimizing loss of muscle mass.

    Coincidentally, he also believed in FAST workouts. He recommended starting out with 30s rest between sets, and working down to maybe 10s or less.

    Compare that to most of the people you see in the gym that spend more time walking around or talking than they do lifting.


  7. Hey Tim,

    This is very interesting, currently I’m trying out what your diet in your lose 20 lbs article does to my body. Although I agree with this article I do want to point out; cutting calories did make the people in the first study lose weight. Although I don’t have scientific proof backing me up I’m pretty sure that the basics of calorie deficit equaling losing weight still stands. Yes it is less maintainable but I think people need to remember you can’t use the excuse that “cutting calories doesn’t work for me.” Unless physics have changed since I’ve taken them (and since I’m just about to graduate I doubt they have) mass doesn’t just appear and since your body uses some food for energy if you eat less calories then your body needs to maintain weight you will lose weight.

    Also I just read your book after following your blog for a few weeks. It was a great read and has changed my plans for the future. Like I said above I am getting close to graduating with my B.S. in computer science and now I’m not looking forward to getting a good job as a means of career growth but I’m looking forward to getting a good job as a means to finance the personal growth that I think will stem from me achieving my dreams.

    Thanks for such a good read!


    • This post makes some really valid points. I myself also agree that calories play a huge role in weight loss. However, it can definitely get out of hand when people become obsessed and this is what leads to the health problems you see in connection with losing weight.

      I truly believe that you can lose weight and maintain it simply by eating controlled portions of healthy foods combined with a good exercise regimen.


  8. Just started following Chuck Norris on Twitter. Tim – I think you should make an exception to your low information diet for him. ; )

    I don’t really know what I think about this. I wonder how much impact the psychology of volunteering for a starvation experiment had vs. volunteering for a weight loss experiment. As Dr. Eades mentions – not quite apples to apples.

    I’ve never experimented with a high protein / low carb diet. I eliminated grains completely while I was a raw foodist (apart from the occasional sprouted grains – which are almost vegetables at that point) – but eliminated all animal products (meat and dairy) at the same time. I had good results – though I think my body temperature was low (raw fooders will say it’s because there are fewer microorganisms introduced to the body and so the higher temperatures required to kill them are unnecessary). Plenty of healthy fats and lots of carbs but qualitatively different carbs, I believe.

    In re-scanning the “geek to freak” article I noticed Tim’s cholesterol drop. I find that interesting, since one of the chief statistical benefits of veganism is lower cholesterol. I also wonder how the high quantities of protein are handled by the liver, as I have heard it can cause strain.

    Tim – you mentioned somewhere about your mom’s struggle with food allergies – I’d like to hear more about that. Her journey, how your family joined her on that journey, how it did or did not inspire your study of nutrition, etc. Though I have never had allergies of any sort, one of the most influential dietary books for me was Nicollette Dumke’s 5 Years Without Food. It stresses the benefits of rotating one’s diet – as opposed to relying so heavily on wheat, corn and soy as the Standard American Diet does.


  9. Tim, I love these types of post that you do. Being a kind of gym rat myself, I’ve always been interested in the anatomy/bodybuilding area, and you do some of the best posts about this stuff (besides of course.)

    I dugg, stumbled, and delicioused this post ;-)


  10. Hi Tim,

    It’s my first time posting but I’ve been a loyal reader for a couple months now, and I have to concur about your sentiments about eating less carbs and eating better proteins and fats. I myself, am experimenting with your slow carb diet that you posted a while back. It is my 3rd week in and I gotta say that I really don’t miss the rice or heavy meats that we Filipino’s love to eat (no rice for Filipino’s is like no water for fish). I’m chronicling my experiment/adventure with this weight loss technique on my blog … inspired by yourself and by my friend Alejandro who dropped a whopping 45 lbs. in the course of a couple months by decreasing carb intake.

    Anyone can feel free to take a look at how I do through the duration of my weight loss. I started at 160 and am trying to get down to 140 lbs.

    On this post itself…the results of both studies are fascinating to say the least. It is true that what matters most is not necessarily how much calories you take in, but rather where those calories are taken from.


  11. Tim – as usual – you are right on. I wrote an essay for a class I took last semester about the fallacies of the USDA food pyramid, which I chose to target because it is an “icon” that people trust. I honestly think that the epidemic of depression in Westernized nations has a lot to do with the push of low-fat diets, and the majority of our other “non-communicable” causes of death (heart attack, stroke, cancer, diabetes to name a few) have a lot to do with the refined grains and sugars that make up the “core” of the old pyramid. There is a revised one, but most people don’t know about it, and it still has its flaws.

    My essay is posted here, if anyone is interested:

    Then on to foods that heal – our bodies really need fresh (local) foods that are pesticide-hormone-antibiotic free, and (getting off my soapbox in a second :)) animal meat (if you choose to eat it) that is fed all of the above. We are what we eat. Eat fresh produce, as raw as possible as often as possible. This is what we *evolved* eating.

    I think what I would like to hear more about (and get more info out there about) is the true causes of depression and other diseases (as mentioned above) being preventable simply by diet. To include ADHD and the like in children. I truly believe it’s that simple, but we are a nation consumed by what we are *told* to eat, and what is readily available; the statistics of causes of death in Westernized nations tells the tale.

    @ Nate: I really like what I have been seeing in Men’s Health. Kudos to you & that magazine. I wrote a little bit about eating fat to lost fat here:

    I happen to know there is a book by the same name, I haven’t had a chance to review it yet. Comes from the same publisher as Nourishing Traditions

    which I have read. A great place to start (with recipes) to learn to eat how we evolved eating, and stay healthy.

    Enough for now :)


  12. Dr. Eades, Tim, fellow readers,

    As a graduate in exercise sciences with experience in coaching people who want to lose fat, I can attest the validity of Dr. Eades’ remarks.

    There really is a growing current in the scientific community that’s recognizing the potential for high-protein and low-carbohydrates diet to help fat loss above and beyond simple the thermodynamics “calories in minus calories out” approach (as Dr. Eades’ pointed out).

    I’d add that your mileage may vary: it seems that the individual response to a low-carb diet differs a lot from one person to another (I’m saying that out of my scientific and practical background). For example, I know for sure that losing weight (for a photo shooting) is terribly easy for me on a high-protein and low-carbohydrate diet. I feel full, my moods stabilize even more than when I eat a regular-carb diet, and my fat % drops.

    If you’ve been trying to lose fat, I encourage you to try it.


    Tim, to answer your question, I’d like to read more on the mechanisms of muscle growth and the best training methods to do that.

    Cheer everyone,



  13. So, which literature do you recommend about low-carb diets (apart from Dr. Eades’ book, of course) that has done it’s homework? bonus points if there’s a spanish edition since my mom is interested in the topic and she never quite learned english


  14. Tim,
    Having read your post, and the related posts, I am left with a conundrum. I am currently training for a 1/2 marathon and marathon, which would lead me to believe that I would need to consume plenty of carbs for my training runs (I am averaging about 25 miles a week, with more to come). Reducing carbs does not seem to be an option.
    I am also a vegetarian, which means my protein sources are limited. I realize that I am a fringe case, but any suggestions for those of us who don’t eat meat? How about for those training for endurance sports?


  15. One possible alternative explanation is that in the Keys study, all food was provided and thus measured by the investigators. In the Yudkin study, it was not.

    There is a pretty big scientific literature showing that self-reported food intake is generally inaccurate, even after training.

    So one alternative reason the participants in the Yudkin study didn’t suffer any effects is that they were not really eating only 1560 kcal/d.

    Also, the Yudkin study was only 2 weeks long, while the restriction in the Keys study lasted 24 weeks. Even if they were eating only 1560 kcal/d, they knew it was only for a couple of weeks. The Keys participants got starved for an extended period of time. How can you even begin to equate the psychological effects of these two studies?


  16. Excellent post Tim! I’d like to hear more about weight GAIN. And I guess it’s not as much about the actual weight as it is increased muscle strength and size. (I want to be strong and look strong, not just weight a lot…haha) Also, I know a few younger people (high school age) that are trying to gain weight and there doesn’t seem to be any consistency to the information we get. According to what you posted and the comments, weight gain powder and other supplements may actually increase your metabolism and make it more difficult to gain weight…even thought that is specifically what it is designed for? And if that really is the case, I can’t imagine what many of the other foods may be doing to decrease our abilities to gain weight. Common sense and conventional wisdom says eat lots of protein and calories and workout and you’ll get bigger. I’ve done that and it hasn’t worked (at least not in any significant amount). You’re good at throwing out conventional wisdom and getting to the point, which is something I really like to see on the subject.

    Very interesting post…I’ve got lots more to research now.


  17. I’ve been in the nutritional cleansing industry for a while and have witnessed hundreds of people lose 20-30 pounds in a month very easily. What I’ve learned is that if your body is being fed all the nutrients it need, which by the way you absoutely cannot get without supplementation nowadays, you don’t need a ton of calories. We don’t crave tons of food if we’re being satisfied with quality nutrition. On my website you’ll read (and see) people who successfully lost 30 pounds in a month and have kept it off for years.

    Thanks for your post Tim. What’s up with all the violent winners this past weekend? I’d love your opinion on the state of our media and where you think it’s headed.



  18. Great read Tim thanks. I believe in low carb diets but I still think those studies show that the people lost weight based on calories ultimately even though they didn’t feel hungry. However that study pointed at by Skyler is very interesting and it seems to indicate that certain fats can boost metabolism levels high enough to lose plenty of weight while taking in high levels of calories. I’ll have to look into that more.

    Also as for Tim’s cholesterol dropping in the Geek to Freek article much of that may be due to the supplements and wine he was taking in as all but possibly the chromate are known to have cholesterol lowering effects.

    Thanks for these types of posts though I really enjoy them.


  19. LOL!

    Dr. Eades,

    This post didn’t have anything to do with the comment I left under your calming video blog post—the one about Tim’s Experiment—did it?

    In any case, it’s great to see this post.


    If you want to laugh your ass off, just have a look at Eades’s blog and look at some of his responses to dumb comments. A funny guy he is…