A Physics-Based Diet Plan

homer-donutThe holiday season is upon us, and for many, this translates into a marked uptick in the consumption of tasty food treats. I’m no different, and can really pack it in on such occasions. For instance, the day after Thanksgiving this year, I stepped on the scale to find myself about 5 pounds (~2 kg) above normal weight. I kicked in my diet plan, and by Monday morning (3 days later) I was back to normal. Resume course. I use a simple formula, backed by physics, that works every single time. The topic is Do-the-Math-relevant for two reasons: it applies quantitative physics to everyday life, and it touches on attitudes relevant to energy/resource conservation.

I’ll spare the suspense and reveal the physics trick (unlike magicians, physicists are all too eager to explain the how and why of nature’s tricks). In this case, your body mass adheres to a simple bookkeeping of mass–in vs. mass–out. Mass comes in by ingesting food and water. Mass goes out by many mechanisms: some obvious, some not. Skipping over the obvious unmentionable forms—often ascribed a numerical sequence of #1 and #2—we also have #3, #4, #5, …

Invisible Weight Loss

A surprising fraction of our weight loss occurs right under our noses—literally. The air we exhale is loaded with carbon dioxide and water that were not present in the intake. Yes, we do grab oxygen out of the air, but these atoms are returned to the air attached to carbon and hydrogen. Our skin also perspires, which is another mechanism for mass loss. So really we’re emitting a constant stream of carbon and hydrogen from our bodies. Brick by brick, these atoms add up to significant mass.

The chemistry is straightforward. Taking a unit block of carbohydrates (like sugars: CH2O), reacting with oxygen (O2) produces CO2 and H2O. Conceivably, all of the carbohydrate mass we ingest could be exhaled by combining it with oxygen. The same applies to lipids, which are comparatively oxygen-free—comprised primarily of carbon and hydrogen. But this is why we also get more energy per gram from fats: because there are more oxygen reductions to reap. By having more on-board oxygen, carbohydrates are already half-reacted.

The math is pretty simple. If we eat a mixture of carbohydrates, proteins, and fats averaging, say, 5 kcal per gram, and have a diet of 2000 kcal/day, this amounts to 400 g (about a pound) of food mass each day (ignoring the non-nutritional and water components of the food). And in steady state, this means we lose a similar amount per day largely by continuing to breathe, perspire, and occasionally “using the facilities.”

Aside: More Weight Loss Math

Another angle on the whole breathing thing: according to Wikipedia, the air we inhale is 21% oxygen, by volume, along with trace amounts of CO2, H2O, etc. Meanwhile, we exhale CO2 at 4–5% concentration, reducing oxygen to 14–16%.

If I assume that each breath is one liter in volume, and that we execute 10 breaths per minute, I calculate an exhalation of 720 L of CO2 per day, which translates to 32 moles at standard temperature and pressure (22.4 L/mol), thus equaling 380 g of carbon atoms at 12 grams per mole. Hey—that’s nearly identical to what we get from the 2000 kcal/day diet calculation!

Water vapor is also an interesting parameter. Saturated air at body temperature contains about 40 g of water per cubic meter. So in the extreme limit of breathing in dry air and exhaling 100% saturated (humid) air at body temperature, our 10 L/min rate would translate to 14 cubic meters per day and 560 g of water each day. This puts water loss via breathing at a level comprable to that of carbon loss.

Two factors reduce the effective mass loss from exhaling water, however. One is that the air we breathe isn’t necessarily bone dry. Air at normal room temperature and 50% humidity contains about 10 g/m³ of H2O—reducing the effect by 25%. But more significant is the question of where the exhaled water originated. If it’s ingested water, count the mass loss at full freight. If it is reacted water from inhaled oxygen, only the part from hydrogen (2 mass units out of 18, or 11%) of the exhaled mass came from ingestion—the rest borrowed from the air as oxygen.

The Diet Plan

Now understanding that the body will continuously shed mass even if the food supply is shut off, we’re ready to examine my dirt-simple, but extremely effective diet plan. The idea is to cut back on the amount of mass that goes in, and let the numbers take care of the rest to balance the books and put me back on target. How do I limit mass in: skip meals.

That’s it? Yes. Stupid, isn’t it. But the math is equally simplistic. As long as you don’t compensate by eating bigger meals when you do eat, it’ll work itself out. I’m not talking about fasting or total deprivation: just miss a breakfast here, a lunch there. Granted, different people may experience different physiological reactions to ingesting less, but even the stingiest physiology can’t beat the mass balance concept. Just keep breathing! The more you breathe (exercise, for instance) the more mass you’ll shed.

A colleague of mine once asked how I manage to stay trim, puzzling over my freedom to eat “fattening” desserts and the like. I told him that I skip meals when I see my weight creeping up. “Oh, I couldn’t do that,” he said. I probed, “Why? What would happen if you did?” He looked at me with a curiously shocked expression and said, as to an idiot, “I’d get hungry!” Is that all? That’s hardly a barrier.

Okay, let me inject some quantitative context in which to view our eating habits. A human, deprived of food but allowed water, may typically live about two weeks before running out of fuel. I don’t recommend experimentation on this front. But all the same, one may miss some 40–50 meals (at three per day) before going broke. If you think of your body’s store of energy as gasoline in your tank, each meal represents about 2% of the total supply. Think about this: our daily routine has us pulling into the gas station with our “refuel light” on when our tank reaches 98% full. We’re essentially always topped off.

It wasn’t always this way in the history of the human animal, and many in the world today do not have the luxury of three square meals daily. The human body evolved to tolerate dry spells. In this context, the hunger we sense when our tank dips to 98% is our body’s way of expressing a preference that we eat.

Alright, it would not be at all healthy to operate our bodies like cars, pulling in to the feeding station once every couple of weeks on fumes. So while the 98% metric provides some startling context, it’s unfair. All the same, we should recognize that the world won’t end if we miss a meal or two.

Battling Psychology

This brings us to the real challenge of diet: psychology. How one responds to the physiological signal of hunger is vitally important. Hunger is an interesting experience. It comes on strong: the stomach protesting with audible growls. I can only assume that for many people, these alarms displace thoughts of almost anything else but feeding the hunger.

I personally respond to these pangs with detached amusement. I think of hunger as a primitive, low-level part of our constitution—akin to our brains that have a reptilian complex underneath a mammalian complex underneath a cerebral cortex. We’re built from simple pieces tracing back to our evolutionary roots. The lower levels control many of our primal instincts, but the final layer of intellect can override the base functions. Much as a chicken going berzerk when the wind blows a backyard umbrella over (true story), or a cat scrambling out of the room at the innocent sound of crinkling plastic (also true), or a child throwing a conniption when peas touch carrots on their plate, I see hunger as overreacting to a non-threatening situation. “Calm down,” I say with a wink.

Ignoring the hunger, I focus on other items of greater interest. Hunger will periodically reassert itself and demand attention, but it becomes a barely-noticed distraction that can be tuned out. Similarly, a barking dog next door may be annoying, but need not consume all your mental attention. I find that after an initial wave lasting an hour or two, the hunger gives up and stops being so annoying. I wonder how many people in our well-fed society know that hunger will not simply continue to build, if left alone? It comes in waves. I can wake up less hungry than when I went to sleep the night before.

A Broader Context

So ignoring hunger is really not that hard. I think it’s a matter of shifting priorities and emphasis, especially in relation to the internal vs. external world. We all have an internal world pertaining to our individual bodies. And we live in an external world that shares an objective reality. A rumble in my stomach has effectively zero impact on the external world, if I decide to ignore it. Because I value the external more than the internal (the shared rather than the “me”), I prioritize the impact I have there. In my rank-ordering, I consider science the most important, fundamental thing, followed by the physical universe that science describes, then the Earth and its ecosystem, then humans, and then me. Perhaps this is an oddly inverted hierarchy.

And here is where the psychology of dieting ties into many other Do the Math themes. My success at vastly trimming down my energy footprint in this world can be tied to an attitude that my personal comfort/enjoyment is comparatively unimportant. I prioritize the “us” over the “me.” I’m just one individual, and my very existence—let alone the fullness of my belly—is hardly important in the grand scheme. But I can have a big positive influence by being less selfish about grabbing goodies just because I am able.

As highlighted in previous posts, my wife and I basically don’t heat or cool our house, tolerating 55°F (13°C) in winter and (occasionally) 85°F (29°C) in summer. We line-dry clothes, limit gratuitous lighting, limit discretionary travel, avoid energy-intense foods (like meat), don’t have kids, etc. These are sacrifices of a sort, and often invite ridicule by those (threatened individuals) who find such practices repellent. I expect similar reactions to my diet technique. But just like I know that huge energy savings may be realized by exercising choice, I know that weight gain is very easily controlled by what you put into your mouth (and how often). The math, physics, and chemistry are on my side. The barrier is in the will. My question is: do we have the constitution to exercise the requisite will to trim down our energy appetite as well as our physiological analog? Show me. Please.

43 thoughts on “A Physics-Based Diet Plan

  1. Excellent post as usual! I will share this with my wife. I once fasted ten days as a teenager and didn’t have any problems. My health improved considerably and the benefits lasted a long time. My wife and I sometimes go without food for 36 hours, and it feels like recharging your batteries. We just drink lots of water to stay well hydrated.
    Keep up the good work!

  2. Finally! Someone who gets it: body weight is a result of running a calorie surplus, and hunger isn’t the end of the world.

  3. Of course, eating smaller regular meals and exercising a bit more works too. Without the hair shirt, mood issues and reduced intellectual performance.

    • I suppose it was somewhat arbitrary: 175 lbs (80 kg) is the target, but I don’t take action until I creep near or above 180 (I am 6’4″, or 193 cm). Less than this and I look skinny; more than this I start showing a baby gut.

  4. It’s worth noting that people have varied physiology; and that no matter how rational we are, we are ultimately slaves to our physiology. For instance, for some people hunger is not just a dull gurgling of the stomach, but can escalate to headaches and non-specific stress (even if not debilitating, such symptoms certainly hamper productivity). For others, not eating on a regular schedule (and skipping meals certainly qualifies) exacerbates underlying digestive issues (with associated unpleasantness).

    My point is just to note that your tactic of skipping meals won’t work for everyone. Of course, the underlying math is correct, so alternate strategies are available: e.g. instead of skipping one meal, eating 50% of your usual amount for the next two meals will also work. (The challenge, as you note, is more one of discipline.)

    • > For instance, for some people hunger is not just a dull
      > gurgling of the stomach, but can escalate to headaches

      That’s me. I used to have frequent migraines, and one sure way to trigger it was being hungry. Sometimes this hunger attack came after two hours of eating lunch, and in a lot of cases, it was unpredictable. The attack was pretty fast (5-10 minutes), and I started sweating and felt as if my stomach as being dissolved in acid. And sure, a strong and debilitating headache — with usually a bonus throw up thrown in — came within tens of minutes. I really had to eat a lot in order to ensure that the headache didn’t become completely debilitating. However, there was one sure way to end this horrible headache: A Burger King Double Whopper Meal, and I am not kidding. Whenever I was on the road and started to feel a migraine (irrelevant how it started), I immediately started looking for a pharmacy – er, Burger King. (other stuff like Big Mac Meal didn’t have this effect).

      Then for completely unrelated reasons, I very severely restricted my diet: I became a complete vegan (diet-wise, not mentally, and enjoy your steak), went gluten-free, and I also avoided starchy foods. I did this since I have a lot of small miseries, and I wanted to see if I was sensitive to something. However, I also kind of expected that the diet would last 2-3 full days, and one of the aforementioned hunger attacks would strike, and the diet would be over. But no, the hunger attack didn’t come. Not only that, I lost over 20 kg, and my headaches became much less intense (barely register now) and rare. Obviously, I am sensitive to something found in animal products. Now I eat gluten foods since I am clearly not sensitive to that, and although I restrict starchy foods, I don’t eliminate them.

      So back to Justin’s statement, hunger pangs can be very terrible and don’t work for all people. (Hey, since I have this diet, I can actually stand hunger).

      Vilmos

    • Justin, any nutritionist is going to tell you that same thing. Eat less per meal and do not freak cause you overate at one meal. Skipping a meal is a bit “radical”. To make a bumper sticker out of this “Do More or Eat Less”. LOL

      • I recently made an amazing discovery, thanks to Facebook of all places…. yes, I know, but please keep up…

        These days, people eat a lot of wheat, and that wheat is very different to that which people ate even 50 years ago. ‘Modern’ wheat contains far more of a protein called Gliadin. Gliadin makes you hungry. People who eat wheat, on average take in 400 kCal MORE energy per day than people who don’t. JUST because they feel hungry….

        So my wife and I tried it. And it works. I’m not exactly on a diet, I put cream in my coffee, have lashings of butter on my veggies, and am prone to chocolate…. which is just about my only source of sugar these days.

        In three months, I have lost almost 5kg (~10 pounds) without trying. I just don’t feel hungry anymore. Well worth a try if you ask me.

  5. Thanks for an excellent post.

    “A rumble in my stomach has effectively zero impact on the external world, if I decide to ignore it.”

    While I have tried the diet method you outline with great success twice, losing 17 lbs once and 9 lbs later in a matter of a few weeks, I have noticed that my mental output as a scientist drops if I eat less. Physically there is little concern but it is harder to work on complex mental tasks. So just nitpicking here that there is some impact on external world that depends on how long one diets and how different bodies and professions are wired. And as you said, it is easier to do if one focuses on something grander.

  6. A hypothetical re your hierarchy of priorities: Let’s say that someone proposed an experiment, and convinced you beyond a reasonable doubt – I mean really CONVINCED you – that by participating in the experiment you would contribute vastly more to science than you possibly could through your continued practice of physics through the remainder of your (likely) years on Earth. Now for the obligatory catch: you will almost surely die in the experiment. Would you kiss your wife, your cat, and your PV solar system goodbye and jump into the experiment?

    • In another instance of allowing the cerebellum (ahem: cerebrum) to overrule the more primal instincts, I would not shy away. I’m not saying it would be easy, but doing trumps being, for me. Such people are not unknown in this world (wartime often brings about sacrifices of similar magnitude, for less apparent gain).

      • Thanks. Tip o’ the hat.

        By the way, I suspect both the rising obesity rate, worldwide, and the history of the last 30 years of hydrocarbon usage suggests that the answer to your closing question is most likely an emphatic “No.”

  7. For the first time my favorite blogger is wrong about something. Yikes. Your diet plan would work perfectly if our bodies were perfect machines that did not vary their output in response to a varied input (i.e. if all of the internal mechanisms ran the same way on two meals a day as they do on three). But that is not the case (and if it seems to be the case for you, just wait a few years :-) A body will change its metabolism based on input, and change its storage efficiencies based on the content of that input. For just one example, I can eat a 1300 kcal/day balanced diet and not lose weight (just feel hungry), or a 1300 kcal/day unbalanced diet (because it contains much protein and zero fat) and lose a pound a day (and feel like stupid crap). What it comes down to is: it’s complicated.

    I’ve written a bit more about why simple formulas like this fail here: http://brent-noorda.blogspot.com/2013/02/calorie-counters-suck.html

    • It’s true that my experimentation is limited to a single corporal instance. And I can believe that bodies adjust to the extent that they can when caloric intake is reduced. But there are some aspects of staying alive that require non-negotiable machine-like performance. The amount of energy it takes to maintain body heat does not change depending on whether or not you skip meals. The mechanical effort to breathe, walk, etc. are set by physics rather than diet. So while you are no doubt right to some extent, there are also very mechanistic aspects to living that are not impacted. So at some point eating less (while continuing to breathe) is guaranteed to reduce weight.

      • Tom, the problem is that neither all foods nor all body mass are created equal.

        Imagine you maintained your exact same caloric intake, but got it all in the form of sugar water plus a multivitamin supplement. Now, start substituting out other extremes — only butter, only celery, only beer, and so on. Different foods are metabolized in different ways, with different metabolic outcomes.

        One of your UC colleagues, Robert Lustig at UCSF, has an excellent lecture online on sugar metabolism. It will give you a good idea of the types of complexity involved:

        http://www.youtube.com/watch?v=dBnniua6-oM

        The other problem with the equation…we often use “excess weight” as a shorthand for “excess fat.” Almost all Americans have much too little lean body mass — muscle, tendons, bone, etc. — and too much fat. Indeed, many “overweight” Americans are below their true ideal weight; what they need to do is gain muscle and lose fat. And muscle is much denser than fat, which is how you can be obese yet under-weight.

        That points to another way that the overly-simplistic physicist diet misses the mark: lean body mass is much more metabolically expensive than fat. The way that exercise burns fat is not through the calories burned while exercising; a single piece of fruit has all the calories you need for a vigorous workout. Rather, exercise prompts the building and maintenance of lean body mass, and that takes a *lot* of calories. Take two people, both the same height and weight, but one an athlete with 5% body fat and the other overweight with 20% body fat; just sitting there, doing nothing, the athlete is burning significantly more calories than the overweight person.

        May I suggest?

        Eat more smaller (but healthy and balanced!) meals; the body reacts to the stress of skipping meals by hoarding carbohydrates as body fat. And regularly do muscle-building exercises.

        The good news is that it only takes about an half an hour a few days a week or so to get adequate exercise, and that you don’t need any special equipment or gym memberships or whatever; your own body is already the best exercise equipment available. There aren’t any secrets to bodyweight exercises, but Mark Lauren, a retired Special Forces fitness instructor, has a well-organized book that lays out simple regimens for any healthy person, regardless of current condition:

        http://www.marklauren.com/

        Again, you don’t have to have any special talent, knowledge, equipment, or anything else; just the dedication to work (very) hard for a few minutes a few days a week; your body will take care of the rest.

        Cheers,

        b&

  8. I like the post and I appreciate your logic. There is a distinct peril to ends up prey of the crazy-dieters debates though, already mildly showing in some comments.

  9. Thanks for helping me understand better mass intake and output in human chemistry. However, this is probably your weakest argued post, your point is old and tried. There are numerous over feeding studies that have called into question this simple calories in calories out math you do. Yes, under feeding will cause you to loose weight, but weight loss is NOT the goal. Health is. The body treats different quality calories differently, even if the total calories are the same. Given the right quality foods people can eat until satisfied, not skip meals, and more their bodies closer to health. Look to our evolution for understanding of human diet and nutritional needs.

    Thanks for this blog.

    • He doesn’t really do any calorie math, it’s all mass based. Your points on how the body treats different types of calories may be valid, but totally misses the point of the post. MASS in = MASS out in a steady state.

      • I will accept your correction: “He doesn’t really do any calorie math”, but to dismiss my point on the body treating different calories differently would be a mistake.

        I will also agree to “MASS in = MASS out in a steady state”, however such a claim is a tautology MASS in = MASS out IS a steady state of mass. A steady state in mass IS MASS in = MASS out. This tell us nothing.

        Yes if you lower your mass (calories) intake enough you will loss weight (not a steady state). Take a look at the twinky diet here: http://www.cnn.com/2010/HEALTH/11/08/twinkie.diet.professor/

        Question is are we just worried about weight loss or about over all health? If we ONLY care about weight then this post is mostly right. Cut back enough and you will loose mass. However his recommendation of a meal or two every so often (or even weekly) might not be enough for some. They may need to cut back very severely to see the effects. Question still is: “Is missing meals healthy?”

        None of that deals with the real question of does this mass in = mass out idea work the other way? If I eat too much will I gain mass? The answer to that seems to be very complex.
        I will once again reference these OVER feeding studies: http://www.proteinpower.com/drmike/metabolism/overfeeding-and-metabolic-advantage/#sthash.4A72i4bR.dpuf

        These studies indicate that mass intake is NOT a predictor of weight. That indeed that body does shed more mass as mass intake increases. The degree of this shed is variable by individual. The important thing to remember is that our bodies are hormonally self regulatory; we stay about the same temperature, our ph is narrowly regulated as is our salt content, iron, and pretty much every part of our bodies. However, any disruption of these hormones leads to a disruption in the homeostasis described above. Weight is also regulated by hormones, also kept in homeostasis.

        The thing about our modern diets is that we eat historically novel foods, in historically novel quantities. This mismatch leads to hormonal disruption! Leads to great pressure on our bodies homeostasis. Sometimes this mismatch leads to weight gain, sometimes heart disease, or diabetes.

        Of these evidence seems to be massing that our bodies treat simple carbohydrates much different than fats, proteins or even more complex carbohydrates. See the youtube video “Sugar: The Bitter Truth”: http://www.youtube.com/watch?v=dBnniua6-oM

  10. Very interesting as always. I would recommend you read Gary Taubes’ book “Why We Get Fat”. He has many stunning examples of problems with the energy balance model of weight gain.

  11. Where I live in the desert we tolerate 0-40 C without heating or cooling. You just stay indoors and wear proper clothing (you look like a marshmallow in the winter and wear a wet shirt in the summer). I’m surprised how reluctant people are to giving up their isothermal living conditions. However, I do need to consume more calories to maintain my body’s homeostasis.

  12. The amount of thermal energy you dissipate from your body changes a lot. I recall you have an IR camera. Try it and see how the temperature of your skin changes, especially in limbs.

  13. I have to agree with many other posters, Tom I think you are oversimplifying the math on this one.

    While you are correct that ultimately starvation will lose weight, physics demands it, the path to getting there does depend on the individual. For example, does a person’s breathing slow down when you are fasting? Does their body temperature drop, even just a little? Do they perspire just a little less?

    I for one notice a dramatic reduction in my perceived energy level when I fast. Is that simply psychology, or does it reflect a decrease in available energy for certain tasks in my body?

    Secondly, I think you vastly underestimate the power of the hunger drive present in many people. You have mentioned before that you believe people can learn to live with more energy frugality if they just give it a strong try. I completely agree with you. However, when it comes to diet, millions upon millions of people have tried every diet scheme you can think of….and the vast majority fail. So the strong try is there, but it hasn’t worked. That indicates to me the drive is a lot stronger than you give it credit for.

    • For me Tom is right on the button. Yes as you say millions of people have tried every diet in the world and failed, but.
      If you want to lose weight there are three ways to do it.
      1, eat less and maintain your current exercise levels,
      2, eat the same and increase your exercise levels, or
      3, for some a form of medical intervention is required.

      I am currently somewhat invalided (injured and immobile to a large extent) and have not cut my intake of food to the extent required. I have put on around 15kg above m normal weight.
      I am still cutting my intake and have lost a kilo in two weeks, xmas will test my resolve. When fit again I will lose the excess kilos and get back to a normal size/shape.

      However there are people with hormonal/glandular/organ type medical conditions that require drugs or surgery to enable them to lose weight in any fashion.

      The hunger drive is only an issue if you are not serious about losing the weight and need an excuse to have that next snack, chocolate or cream bun. I work with someone who loses 15kg every year to keep his licences etc and once the doctors have cleared him it goes straight back on.
      A lot of it is to do with what you eat unless you have a physical issue, and even then what you eat is important.

  14. First time visitor, interesting blog.

    Just wanted to point out the post totally ignores the impact of hormones on weight gain/satiation as well as the effect of different macros on the body.

    Agree with the guys arguing the energy balance equation is too simple to be useful.

  15. I am super skinny and no matter how much I eat I am always skinny. Just a little bit of exercise keeps me trim. So I agree that everyone’s metabolism is different. I found that when I did a lot of juicing and ate really healthily I could go all day without eating and not get tired or hungry. If I eat less healthily then I get hungry every few hours, so I think what you eat plays a big part in how your body accesses energy, and how comfortable going without food will be.

    Apparently people who starve or are anorexic have metabolic changes so that when they do finally start eating the body hoards calories and they become fat much more easily.

  16. This is an interesting one, I’ve done much the same thing but more slowly this year. I’ve been skipping occasional meals (usually lunch) for semi-valid financial reasons – i.e., I’m not too broke to eat, not by a long way, but I’m trying to be disciplined about my food shopping. So if I’ve run out of the sort of things I like to have for lunch, *and* there’s no leftovers from the previous evening’s meal, and I have some days to go until the next planned shopping trip, I don’t eat lunch. For the same reasons I’ve cut down on snacks/treats and beer. Not much, mind, because my beer is home-brew and hence very cheap :)

    Anyway, the result is that I’ve lost about 20 pounds over the past year-and-a-bit (I didn’t really weigh myself from mid-2012 until last week…) without really trying, although it’s certainly not unwelcome.

    That said, I can second the comments that skipping meals does seem to affect my mental performance, but since I’m unemployed because of unrelated health issues, that’s not usually a problem…

  17. “My question is: do we have the constitution to exercise the requisite will to trim down our energy appetite as well as our physiological analog? Show me. Please.”

    In all the complaining about the oil companies and the coal companies and capitalism and empire and all that, as the basis of our on going destruction of the environment, the example of Tom’s household energy consumption stands in sharp contrast.
    We could cut our CO2 emissions in half tomorrow….. if we chose to.
    We make the choices at what levels to heat and cool our homes, and what mileage our vehicles get and how much we drive them.
    The oil and coal companies can only sell that stuff if someone buys it.

    Miss a meal?…… Put on a sweater and turn down the thermostat?…..
    Why?….. The American way of life is not negotiable.

    • But one of the fundamental problems with economics is that there are 6.9 billion other people on the planet who don’t share your concern for the environment or our future who would be more than happy to take the place of your voluntary reduction in consumption.

      And unfortunately our societies are hammered with media propaganda that is designed to get people to consume consume consume, even if it means getting into too much debt, because that is the only way our economies can avoid collapse, as the financial system is a ponzi scheme that must continually grow. If everyone started consuming half what they do now, unemployment would skyrocket and everyone’s investments that return a positive return as a result of economic growth would all tank.

      The system is flawed to its very core and it will only get fixed with a complete rework from the top down. I am afraid that this will not end until it is forced to in the final collapse, at which point it will be too late, because almost all economists still believe that economic growth is a good thing that must be maintained. They seem to take no interest in learning the fundamentals about how economies work, i.e. how energy powers it all, yet doesn’t even get a mention in any of their textbooks. Just look at all of the bizarre arguments they have come up with in comments on this blog in previous posts trying to justify and rationalize how growth can continue, when it clearly can’t. Their attitudes will not be changed.

      This will all end very very badly. That, I think, will be how the story of modern humanity plays out.

  18. Reading this entry reminds me of watching the documentary film Supersize Me, where the guy and his partner are both vegetarians, and (after the guy experimenting with a fast food diet for a period) they both are back eating a veg-only diet, both expressing the general sentiment “mmm…god I love veg. veg is good. veg. veg.” etc.

    Recently while browsing the guys documentaries on IMDB, I found out his partner had secretly been eating meat the whole time, and was even (if I recall correctly – may be mistaken) a nutritionist or life coach or such at the time, advising others to go on a veg diet, and actually felt seriously guilty about this the whole time. Found that quite funny.

    So, the connection to your blog post:
    You have less control over your mind than you think ;) (and this goes for everyone else too – some even less than others as well)
    What you’ve got to remember, is that when you skip meals, you also change how your body gains energy to utilize in powering your mind as well, and gaining this energy totally from ‘reserves’, rather than also from food that is being digested, seems to be less efficient and means your mind will not run at full capacity for the day.

    For a scientist, this is bad and unproductive. I do a lot of programming work, and this is precisely what I experience:
    If I skip meals and try to let the hunger pass, I can not be doing work at the same time, otherwise I will be at sub-par performance, and will be battling with myself to get enough work done.

    So, this is an interesting post and the physics of it all make sense – but if you’re going to skip meals for losing weight, be prepared to also not be at your best intellectually as well :)

    ~ John

    • Someones earlier point, that missed meals can lead to headaches, is especially relevant to me as well – I can get migraines if I don’t manage my diet carefully, and one of my triggers can include skipping meals.

      Headaches (migraines in particular), seem to be sensitive to the digestive system.

  19. Whether it’s the cerebrum or the cerebellum or what, it sure looks like a lot of people’s brains aren’t working right. Some how they aren’t making the connection that actions in the present have consequences in the future. They don’t know debt from income. Back years ago it dawned on me that as we get older our systems don’t work as well and we get weaker. I couldn’t do anything about getting older. But I could do something about how much weight my weakening body had to carry. In the last ten years I have lost a hundred pounds attempting to do what I can to address the physiological facts of entering the medicare years. We have a choice about what we put in our mouths just as we have the choice of where we set the thermostat. Several previous comments brought up the issue of different people having different metabolisms. We might assume that these individual metabolic difference that we see manifested in the expanded waist lines of our citizens are being paralleled with differing individual brain functions that manifest as the changing composition of our environment. We are rapidly creating a set of conditions that are not human friendly. The ability to see the facts and the will to take action based on those facts is missing. The good news is that we live in an infinite universe so all the drama and tragedy that humans come up with isn’t all that big a deal. People come and people go. Species come and species go. Planets come and planets go. Stars come and stars go. Galaxies come and galaxies go.
    While we’re here, making good choices feels better.

  20. TM, I always enjoy your posts but this time I believe that the physicist eagerness to simplify as much as possible overrun you. I’m also a physicist and I like this kind of experiments. Essentially, If I need to eat (in calories equivalent or which ever definition you want ) 500 g per day and I don’t eat for 1 day a reduce my weight in 0.5 kg. In 2 days 1 kg. But you cannot go like this for ever, obviously. The reasons have been outlined by other participants.
    Anyway the may objection is that your theory is correct, but only in first order. The gain /loss coefficient varies with weight, it is not constant as you post suggests.

  21. In a TedX talk “The mathematics of weight loss”, former physicist Ruben Meerman calculates that body fat turns into 84% CO2 and 16% H2O by mass. I didn’t follow his reasoning exactly, but it’s at 16:45 of http://youtu.be/NGKLpYtZ19Q

  22. Intermittent Fasting is what this post describes, google it.

  23. Hi guys,

    …if you get the chance check out Dr. Michael Mosely’s Horizon called “Eat, Fast and Live Longer” and the resulting 5:2 diet.

    Headaches usually associated with insufficient water intake; when you skip food you also lose their %bulk fluid. Need to correct for that with plain water; that will really help.

    :)
    Merry Xmas all!

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