Fat Kids And Thermodynamics

      30 Comments on Fat Kids And Thermodynamics

Dr. Robert Lustig, who became a YouTube sensation with his outstanding speech Sugar: The Bitter Truth, wrote an essay a few years ago titled Childhood obesity: behavioral aberration or biochemical drive? Reinterpreting the First Law of Thermodynamics. I’d try to summarize it, but it’s already so brief, I don’t think I can. So here it is:

Childhood obesity has become epidemic over the past 30 years. The First Law of Thermodynamics is routinely interpreted to imply that weight gain is secondary to increased caloric intake and/or decreased energy expenditure, two behaviors that have been documented during this interval; nonetheless, lifestyle interventions are notoriously ineffective at promoting weight loss.

Obesity is characterized by hyperinsulinemia. Although hyperinsulinemia is usually thought to be secondary to obesity, it can instead be primary, due to autonomic dysfunction. Obesity is also a state of leptin resistance, in which defective leptin signal transduction promotes excess energy intake, to maintain normal energy expenditure. Insulin and leptin share a common central signaling pathway, and it seems that insulin functions as an endogenous leptin antagonist.

Suppressing insulin ameliorates leptin resistance, with ensuing reduction of caloric intake, increased spontaneous activity, and improved quality of life. Hyperinsulinemia also interferes with dopamine clearance in the ventral tegmental area and nucleus accumbens, promoting increased food reward.

Accordingly, the First Law of Thermodynamics can be reinterpreted, such that the behaviors of increased caloric intake and decreased energy expenditure are secondary to obligate weight gain. This weight gain is driven by the hyperinsulinemic state, through three mechanisms: energy partitioning into adipose tissue; interference with leptin signal transduction; and interference with extinction of the hedonic response to food.

Notice that Lustig is calling for the First Law of Thermodynamics to be reinterpreted, not repealed. He isn’t denying that when kids gain weight, they’re taking in more calories than they’re expending. But as an endocrinologist who’s worked with a lot of obese kids, he knows better than to simply blame obesity on consuming too many calories and let it go at that. As he said in his first interview with Jimmy Moore, “No child chooses to be obese. The quality of life of an obese child is the same as a kid on cancer chemotherapy.”

Lustig also pointed out that there’s been a sharp rise recently in the number of obese six-month-olds. Are the obese six-month-olds taking in more calories than they’re expending? Yes, of course. But unless we’re going to start blaming babies for eating too much and exercising too little, the laws of thermodynamics don’t provide an explanation or a solution. Lustig knows that from experience.

Some years ago, he worked with a group of kids who had brain cancer. The cancer treatments were successful, but later the kids became obese. According to their parents, the kids had developed enormous appetites and become sedentary. As Lustig put it, they spent all day sleeping or sitting in front the of the TV and eating Doritos.

They were clearly consuming more calories than they were expending. But luckily for the kids, Dr. Lustig is blessed with the intelligence to distinguish between how we get fat and why we get fat. Consuming more energy than we expend is how. But the how doesn’t explain the why, any more than “your car is burning more gasoline per mile than it did a year ago” explains why you’re getting lousy mileage.

As an endocrinologist, Lustig understood that the change in behavior was being driven by a change in biochemistry. He suspected that as a side-effect of the cancer treatments, the kids were over-producing insulin. Tests confirmed his suspicion.

Now he knew why the kids were becoming obese, not just how. The high insulin was driving a disproportionate share of what the kids ate into their fat cells. With the energy being stored away instead of burned, they were hungry and tired all the time. So they ate more and sat around.Β 

After recognzing the cause, Lustig gave the kids an insulin-suppressing drug. As he told Jimmy Moore:

“When we gave these kids this drug that blocked insulin secretion, they started losing weight. But more importantly, something that was even more amazing, these kids started exercising spontaneously. One kid became a competitive swimmer, two kids started lifting weights, one kid became the manager of his high school basketball team … Changing the kids’ insulin levels had an effect not just on their weight, not just on their appetites, but on their desire to engage in physical activity.”

Lustig didn’t tell the parents, “Well, it’s a simple matter of thermodynamics, so we must deal with imbalance between the calories in and the calories out. Tell your fat kid to eat less and move more.” And he didn’t (thank God) tell them, “Your kid is producing a high level of insulin, which according to an article I saw on the internet is actually a fabulous appetite suppressant, so don’t worry, he’ll start eating less any day now.”

Nope. Lustig recognized the actual cause of the problem, so that’s what he treated, not the symptom. When insulin was high, the kids stored too many calories as fat, so they ate more. When insulin was low, they burned more calories, so they ate less. You can correctly apply the laws of thermodynamics to either situation — but they won’t tell you anything useful.


30 thoughts on “Fat Kids And Thermodynamics

  1. Laurie

    Love this astute analysis of yours and Dr Lustig’s. These posts remind me of some of the epiphanies I had while reading GCBC. The picture of the woman with the rare disorder of anorexia and emaciation above the waist and obesity below, and Dr. L’s observation and comment about the increase in obese 6-month-olds- genius.
    Laboratory bomb calorimeter calorie counts from burning sugar (yield 4 cal/g) v burning fat (9 cal/g) apply to those limited conditions in the bomb- closed system that reaches equilibrium. We humans (I’d like to demand) are open systems, exchanging stuff with the environment, and not in equilibrium- which when we do reach equilibrium, we’ve just died. And about those bombs in the lab. You can burn indigestible-to-us fiber and glean 4 cal/g, but we can extract exactly zero, zip, nada calories from fiber. So maybe the bomb cal. results DO NOT APPLY to us. And let’s take a car. When cars take in food/fuel do they spare some of the fuel at every feeding for non-fuel purposes? Do they, for example, rebuild their own engines or transmissions a little at a time, each and every time they eat? I know my car doesn’t, but I know for certain that each time I eat ANIMAL FAT PROTEIN AND CHOLESTEROL, I use some for fuel and some for brain and body maintenance, rebuilding and function.

    I ended up watching Lustig’s speech again last night after posting this. I’d forgotten that he dealt with the misinterpretation of thermodynamics in the speech as well.

  2. dlm

    Yes. Diabetes 2 makes you fat and lazy. Not the other way around. You and you body don’t suddenly decide to be lazier and become fatter than you were. Something slows you and your body down, then the diabetes becomes apparent when looked for.

  3. Brian

    When you start the comedy tour for this (ahem), you can ratchet up the reasons for attending by offering CEU’s. πŸ™‚ All the trainers, doctors, nutritionists and other experts will be entertained and best of all, they get to keep their certification. This would have a better and bigger impact than anything the so-called celebrities have done in Haiti, for example.

    There you go! I’ve noticed how professionals can only seem to get their continuing education credits in places like Hawaii … this would give me an excuse to go.

  4. Dave Dixon

    The First Law of Thermodynamics is a constraint, something you know will be true of any physical system regardless of how it works. Gasoline-powered cars and electric cars operate by very different mechanisms, but both will “obey” the first law. As such, the first law doesn’t help you if your car is broken, since it is true no matter what kind of car you have and regardless of what is wrong with it. See also my latest blog on how the First Law of Thermodynamics applied to toilet repair.

    Love it. Here’s a link for others who don’t regularly read your blog:


  5. Isabel

    I am now smart enought to know that you can have good glucose control and still have high insulin levels. Many MDs only check for glucose levels and fail to consider insulin levels. Do you know what kind of drug was prescribed to block insulin secretion in the study?


  6. Kicking Carbs to the Curb

    Fascinating. My toddler is a chunk despite being fed a low glycemic diet so this is an area of interest for me (I suspect my insulin resistance had some negative impact on her even in utero). We limit carbs and push activity and yet her body insists on being built like a tank.

    I’m curious, what was the drug he used? Metformin?


    It was octreotide.

  7. David

    Nice post, Tom. I am still stymied by the lack of understanding among health professionals on this issue. A co-worker’s 40 year old son was diagnosed with type 2 diabetes last week. He was placed on a 2000 calorie/day diet. 1/2 of the diet was carbohydrates. NOOOOOOO! I met with his wife yesterday to relate my experience with diabetes and low carb. She was very receptive, so we’ll see what happens.

    I hope you get through to them. Perhaps Dr. Bernstein’s book would be useful:


  8. Lori

    Given the cycles, feedback loops and lack of direct control over metabolism, it seems to me that if you were going to apply an engineering discipline to metabolism, control systems would be more useful than thermodynamics. Of course, if you don’t apply endocrinology, your model will be nothing but garbage in, garbage out.

    Re: weight gain and medications, one reason some people with diabetes II are overweight is their medications. I have an aunt and a cousin who had unexplained weight loss shortly before their diagnosis of diabetes II. According to one theory, diabetes II can cause cells to starve, causing you to burn your own fat and lean mass. Once they started taking medications, they gained the weight back. As Gary Taubes said in one of his podcasts on Jimmy Moore’s site, sending excess nutrients to fat cells may actually protect you from diabetes.

  9. Brendan

    Thanks for the summary of Dr Lustig’s essay. I think it will take some time before other experts realize the root of the obesity problem:


    β€œThe guidelines are about controlling caloric intake, increasing the calories you burn by moving more and sitting less, and eating more fruits and vegetables and cutting down on sodium, sugar and fat,” Secretary of Agriculture Tom Vilsack said during a briefing to launch the report.

    The USDA will probably be the last organization to get it right.

  10. Katie @ Wellness Mama

    Glad to see doctors finally acknowledging the cause of the problem, and not just telling parents to eat more. I would say, that just medicating the kids is not the only answer, as parents should focus on changing diet as well, not to reduce calories, but to provide better sources of healthy foods (good fats, proteins, veggies) and cut back on the foods that are sparking the insulin reaction in the first place. At the very least, dietary changes should accompany any medication to make it more effective, and because these foods (healthy fats, proteins and vegetables) are excellent sources of nutrition for kids.

    Lustig pointed out that this was a rare situation, kids suffering side-effects of cancer treatments, and he wouldn’t prescribe the same drug for weight loss.

  11. Sarah

    Isn’t that a little dangerous to block insulin secretion? It is after all a protective hormone to prevent high blood sugar from killing you. Were the parents told to reduce the child’s carb intake as well to prevent high blood sugar? Or did they spontaneously just exercise to burn it off before high blood sugar could have an effect?

    Did you see Jimmy Moore’s video about the USDA refusing to the believe there’s sufficient evidence behind carbohydrate restriction? I flipped.

    Their bodies were producing much more insulin than was necessary biologically. Dr. Lustig no doubt monitored their blood sugar.

  12. Jason Sandeman

    To Lori: As a type 1 diabetic recently (almost a year ago) diagnosed, I can tell you what happens with the cells as an uncontrolled diabetic. They are literally starving, so they turn to the only source of energy they have, and that is protein and fat. That is why you have the unexplained weight loss. Also, as soon as your body starts to listen to insulin, (or you give it via shots) you gain weight back. I found this out the hard way, gaining almost all of the 60 pounds I lost.
    I also got the whole spiel of the “carb” diet. In fact, my diabetes “training” was to look at a piece of bread as 3 sugar cubes. I needed 15 or so cubes a day.
    What hogwash!
    I second the Dr. Bernstien book advice, it has been a godsend to me!

  13. Isabel

    Just looked up Octreotide. This is an IV drug that “acts like somatostatin; inhibits multiple hormones including growth hormone, glucagon, insulin, LH, and VIP.” It is used to treat acromagaly and certain cancerous tumors. I suppose it won’t be used on the general public anytime soon.

    No, Lustig was clear that it’s not a weight-loss drug for the general public.

  14. Margaret Wilde

    Little children are often fed salty food and this can cause salt sensitivity and sodium retention/fluid retention. Children are especially vulnerable to salt because of their small size and small blood volume, and because their blood vessels are weaker than those of adults. Salt, and the water it attracts to it, can more easily distend weak blood vessels than fully mature ones. The resulting increase in blood volume and other fluid retention results in weight gain, as well as higher blood pressure and many other undesirable consequences. The smaller the child, the less salt they should have – and a baby, of course, should have no added salt at all. Children made fat by being fed salty food will lose weight fast if they eat less salt.

  15. Lori

    Re: thermodynamics again, if you went on a trip and drove your car at a slow, even speed and shut off all the accessories, and low and behold, you saved gas compared to making the same trip with the A/C blasting and racing to the next red light, this shouldn’t surprise anyone. Only a knucklehead would say that violates the laws of physics.

    That’s right. Same thing when a well-tuned car gets better mileage. No laws of physics are violated.

  16. Galina L.

    Poor children! I wonder, why their cancer treatment caused them to secrete abnormal insulin amounts in the first place? The answer may help us to understand better the insulin resistance development.
    When I think about the rise of the obesity, children looks like true victims here. We can make our own decisions and pay for it, they will pay for our mistakes. It is the first reason why I am so disappointed with the USDA guidelines. It will affect children more then adults.

    Lustig speculated that the cancer treatments may have damaged the vagus nerve in the brain, which resulted in their brains being unable to sense leptin, which in turn caused the pancreas to produce more insulin. I don’t pretend to fully understand the biochemical pathways, but that was his explanation.

  17. Howard

    Why can’t they use that insulin-blocking drug for obese adults?

    Dr. Lustig told Jimmy Moore there are too many side effects for use as a general obesity drug.

  18. js290

    @Sarah: Dr. Rosedale points out lowering blood sugar is only a side effect of insulin release. Insulin tells the cells to take in nutrients, glucose being just one of them. Low insulin levels encourages .ipolysis (fat burning) which is healthy. Regardless of the diet, the goal should be hormonal balance so that fat is the primary source of fuel.

    @Lori: Distributed, adaptive system. As Dave Dixon pointed out as well, energy will be conserved in such a system.

    @Dave Dixon: Speaking of toilets… Calorie counters, if they were actually counting correctly, would have to also have to collect the fecal content of their toilets and burn it in a calorimeter for the “calories out” part of the equation.

    I posted a reply to Jimmy Moore’s podcast episode with Gary Taubes. In doing so, I finally remembered how heat (calories) is related to mass (fat or lean or otherwise): E=mc^2.

    Dr. Kurt Harris has a series of new blog posts trying to change the language we use when talking about food and nutrition. It’s amazing how stupid talking about calories in this context is.

  19. Laurie

    Off-topic, have you seen this from the BBC?

    “World ‘failing to treat high cholesterol’ ”
    I normally ignore such stuff, but please help me keep the faith here. My daughter (who generally believes me and has read The Vegetarian Myth, and watched Fat Head) is struggling with questions like, how can ALL the people be misinformed on this topic? Statinators are greatly and dangerously misinformed, and it’s spreading.

    Oh my lord … head-slap … head smack on desk … tossing the nearest object across the room … have these idiots never heard of the Cochrane review showing that statins are ineffective for people who don’t actually have heart disease?

  20. Leta

    Tom, your posts lately have been fantastic. This was a debate that we had in my last year of undergrad, Kcal-in/out vs. acknowledging metabolism. I wish your site was around then.

    Oh, and, BTW, what was the name of the drug… I kid, I kid. I read all the comments. πŸ™‚

    Did you hear that Weight Watchers has changed their system? It’s still not a low carb diet, but it has turned unprocessed fruits and veggies (except for really starchy stuff like potatoes and corn) into freebies, and upped the points value of starchy/sugar simple carb stuff. They based this move on “cutting edge research from Europe that indicates that fiber and water filled processed foods are metabolized differently by the body and increase satiety”. The really funny part about this is that this was regarded as common sense before the lowfat revolution happened. I’ve heard from my grandparents and read stuff from the ’20s that all says pasta, bread, potatoes, and desserts should be avoided to lose weight. Really, that’s less low carb and more low starch, but the point remains.

    I sort of beat the thermodynamics topic to death, but I really want people to understand that calories in vs. calories out doesn’t explain why we get fat.

  21. Ricardo

    Our body weight is determined by our hormones Key players include Insulin Growth Hormone Thyroid Hormone and Testosterone and to some degree DHEA

  22. dawn

    Interesting that he references the same 7 country study that you mentioned in fat head as being faulty- only has the 7 countries that fit the pattern- and he also doesn’t include the countries that didn’t fit.
    I will miss my coke!

    Yup, he was more interested in the fact that Keys didn’t bother to analyze the numbers to see if sugar might be the problem.

  23. Lori

    @Laurie, to my mind, it’s not a matter of being misinformed so much as not digging deeper, thinking harder or reading with a critical eye.

    @Tom, may I humbly submit the idea that frustration is possible only when expectations exceed reality. (Hat tip to Alain De Botton.)

  24. -V

    Keep beating the thermodynamics topic to death (at least occasionally)– the last couple of weeks have been really good stuff. Not that your blogs aren’t typically RGS…

    Thank you.

  25. Bobby

    wouldn’t a reduction in insulin levels require a low-carb diet? Because without proper levels on insulin, wouldn’t the blood be poisoned by an overly-high blood sugar? I’m probably just missing something. Also, is Metformin included in this list of insulin reducing drugs? Because I know that Metformin is supposed to be an insulin sensitizers, not an insulin reducer per say, but perhaps it is the same idea.

    Their bodies weren’t producing excess insulin in response to carbohydrates or insulin resistance, as would happen with your or me. It was caused by changes in the brain, a side-effect of cancer therapy. So Dr. Lustig chose to suppress the insulin. He did notice, by the way, that as a result of the drug, the patients spontaneously consumed fewer carbohydrates. Since excess insulin wasn’t pushing blood sugar down, they stopped carving glucose-producing foods.

  26. Richard Tamesis, M.D.

    I found a good comment by Andrew Hoffman in http://tinyurl.com/4756qz6 about the misuse of thermodynamics. As he says:
    “According Bray’s thermodynamics argument, wearing sweaters makes you fat. This illustrates the greatest fallacy of trying to apply the 1st Law to a human: it makes the implication that living organisms consume kilocalories for the purpose of generating heat rather than perform useful work (i.e. breathing, contracting cardio and skeletal muscle, generating nervous action pulses, etc.). In reality heat is the waste product of basal metabolism. The first law does not distinguish between different types of energy. Heat, work are all equal under the First Law of Thermodynamics.”

    Good points. I guess according to Bray, I could lose weight by turning down the thermostat in my house.

  27. Matt

    Excellent post, the only objection I had throughout was the anecdote about the boy with ADD.

    Though diet is certainly a factor in everything, I think ADD is one of those things (like cholesterol) that was created by the drug industry, and is now taken way too seriously. Teacher can’t handle a kid: ADD, kid wants to be outside and can’t sit still: ADD. Kid ate some sugar for lunch: ADD.

    I agree that diet certainly contributes to hyperactivity. But I think hyperactivity is hyped by the drug company to be way more than it actually is. Also, in the bottom half of the post you explain how a high sugar diet/high insulin release leads to less excercise, but then you also claim that it causes hyperactivity.

    As I said, I agree that it could be a part of the problem, but not as large a part as the pharma companies that rep ADD as an actual disease.

    I agree that ADD is over-diagnosed for the purpose of selling drugs. In some districts, schools also receive extra money for students labeled as ADD or ADHD, which can tempt them to put a lot of kids in those categories.

    Sugar sends kids (and adults) on a blood-sugar rollercoaster, hyper and unable to concentrate, followed by a crash. True hyperactivity (by which I mean chronic instead of a temporary sugar buzz) is, paradoxically, apparently a result of chemical depression. That’s why hyperactive kids are given ritalin, which is a stimulant. Of course, I believe we should look to the diet first and only use the drugs as a last resort.


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