
"A calorie is a calorie" violates the second law of thermodynamics - krishna2
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC506782/
======
apinstein
tl;dr version:

Calories derived from fat vs protein vs carbohydrates have different
inefficiencies in converting them from their theoretical caloric value to
their useful work in the body.

Fat is the most efficient with a loss of just @ 2-3%, carbs are at 6-8%,
protein 25-30%. [edit Most of] this loss is in the form of heat.

It was not mentioned why this excess heat would not simply be offset by the
body avoiding the normal processes it takes to maintain body temperature.
Presumably the body generates enough heat as a by-product at room temperature
and thus there is nothing the body can back off of to make use of the waste
heat described above.

~~~
kenjackson
Funny, I learned this in nutrition class about 20 years ago. It's something
that clearly has been known for a long time, yet its never been popuar in the
common discourse.

~~~
Udo
Exactly. I also believe it doesn't really matter, because the inefficiencies
of converting sugars to body fat are pretty much irrelevant. Proteins may have
a more significant inefficiency, but it's hard find food where they are the
majority component.

When people overeat grossly, those 5% won't make much of a difference. On my
binge days, I consume upwards of 5000 kcal and it doesn't really matter if
it's actually just 4750 kcal - it's still too much.

So yeah, in practice, a calorie is pretty much a calorie.

~~~
colomon
Huh? Just because one can binge so much that the difference is irrelevant
hardly means that the difference isn't important in general.

The study this cites early on suggests that a low-carbohydrate diet with N
calories a day is roughly equivalent to a low-fat diet with only 70% of N
calories a day. So a 2000 calorie-a-day low-carbohydrate diet is equivalent to
a 1400 calorie-a-day low-fat diet. That result is _huge_. (And makes me regret
having had pasta three times this week!)

~~~
Udo
I allege that it indeed makes very little difference, except in cases where
people indeed manage to eat only one category (most food is a mix, even when
people claim to be on a <insert here> diet).

As other people said, the results of this study are not new. We learned that
in basic biochemistry when the metabolic pathways were discussed.

> So a 2000 calorie-a-day low-carbohydrate diet is equivalent to a 1400
> calorie-a-day low-fat diet.

It is _so_ not.

~~~
colomon
"A low carbohydrate group (LoCHO = 1800 kcal for men; 1500 kcal for women), a
low fat group (LoFat, 1800 and 1500); a third group also consumed a low
carbohydrate diet but an additional 300 kcalories were provided (LoCHO+300,
2100 and 1800). The order of average amount of weight lost was LoCHO = 23 lbs,
LoCHO+300 = 20 lbs LoFat = 17 lbs." That's not quite the same math I used, but
it seems to pretty strongly suggest that a LoCHO+600 group would have have
lost 17 lbs, exactly the same as the LoFat group.

Perhaps there is some reason to doubt this study, but saying "It is so not" is
hardly a rational rebuttal.

~~~
fijal
Provided you assume those effects are linear, then yes. There is however no
evidence for that.

------
run4yourlives
"A calorie is a calorie" is good enough, however.

People aren't fat because they are consuming 2500 calories from a Big Mac and
Fries rather than 2500 calories from carrots. People are fat because they are
consuming 6000 calories and burning off 1300.

The message is simplistic, sure. For a large majority of overweight people
though that's all that is required. Somewhere between reducing caloric intake
and becoming fit, the message that not all calories are created equal sinks
in, if for no other reason that it quickly becomes apparent that you'll starve
only eating one meal of McDonald's a day.

~~~
ugh
Simply counting calories will reduce your weight. I can pretty much confirm
that now. Over the last eight months I tried to stay below 1900 calories per
day and I have lost 17 kilo. As much as I wanted to, I did not manage to
change my diet in any meaningful way, I’m just eating less. I didn’t even
manage to keep up a regular sports routine. But my fallback – mercilessly
tracking my weight and counting calories – saved me. (I would very much want
to eat better. Many of the things I’m eating now have so high calorie
densities that I can only eat very little of them.)

I do know that I will have to track my weight and count calories for the rest
of my life. That’s ok. (As a teenager I already lost a substantial amount of
weight with the same method but I gained it all and more back because I
stupidly stopped tracking my weight and counting calories. I’m confident that
I won’t make the same mistake again.)

~~~
keeptrying
If you simply cut out carbs you will lose a ton of fat.

But yeah if you want to eat carbs and be healthy you have to basically count
calories for the rest of your life.

~~~
ugh
Changing my diet never worked for me. Counting calories does. Also: I do love
pasta.

Counting calories is not that hard. I can do it in my head by now. Tracking my
weight (which, I think, is equally important, especially for motivation) is
more or less a reward and not a chore by now.

~~~
teyc
There is also some research that suggests fasting being beneficial in
modulating insulin resistance. I try not to consume food after a certain time
at night. It is not too difficult to do, and definitely stops short any
thoughts of a late night snack.

~~~
ugh
I'm very skeptical that fasting is healthy, it probably is not. The only thing
I do care about is losing weight and that works.

~~~
eru
Read up. Fasting can be quite healthy. (The only actual debate is on how good
it is for you, not on how bad.) Especially intermittent fasting.

------
jvdongen
The car/fuel analogy is a bad one. High-test fuel only makes sense if the
engine in which you intend to burn it is designed to actually make use of its
qualities to reach higher efficiencies (e.g. a higher compression ratio). If
not, you're just burning more expensive fuel at the same efficiency.

That said, what really interests me is the mechanisms behind addictions. Why
do smokers smoke, knowing full well by now that it will kill them earlier than
non-smokers? Why stuff obese people themselves, knowing full well that it will
cause serious health issues down the line.

Bottom-line I tend to agree with those who hold that 'a calorie is a calorie'
and simply cutting down on food intake is a good enough principle, though
perhaps not entirely scientifically correct, for the majority of obese people.

But why don't they do it? What makes it so attractive that they simply ignore
the serious long-term disadvantages - and even in some cases deny the
existence of said disadvantages even though in reality they must know they are
real.

~~~
janjan
> That said, what really interests me is the mechanisms behind addictions. Why
> do smokers smoke, knowing full well by now that it will kill them earlier
> than non-smokers? Why stuff obese people themselves, knowing full well that
> it will cause serious health issues down the line.

Let's take this one step further: Is the reason/mechanism a smoker smokes the
same why I browse reddit and HN all day instead of working on my PhD?

~~~
eru
Probably not completely the same. There's a variable reward schedule behind
browsing HN (and that can be addictive). Smoking seems to give a different
`reward'.

------
rbanffy
This is not be the Richard Feynman you are looking for:

<http://en.wikipedia.org/wiki/Richard_D._Feinman>

------
stcredzero
Here is an example that one of the best "rocks to look under" (as in pg's
"What You Can't Say" essay) is _the misapplication of fundamental laws_ :

<http://news.ycombinator.com/item?id=2254906>

The researchers who wrote this paper looked under that rock. (In this case,
pop-science application of fundamental physical law. It's hard to get more
fundamental than thermodynamics.)

(An example for you entrepreneurs out there, I'd suggest looking under
Kerchoff's Law. Yes, it's a great principle to keep in mind when designing
security tools like ciphers and cryptographic protocols. However, I contend
it's applied in a counter-productive way when people think about real-world
systems -- those have boundaries that are way too complicated for the
application of Kerchoff's Law. Often, this is just an opportunity for someone
to show they understand crypto theory, then throw up their arms and declare
nothing can be done. However, the truth is that security often works or
doesn't work because of the _economics_!)

------
thirsteh
I thought that "Richard Feinman" was just a misspelling of Richard Feynman,
then I noticed the dates. That would be just like him to author something like
this though.

~~~
dmarquis
Its a good first approximation so to a physicist it might as well be true.

~~~
daoudc
Ouch. Yes, I clearly remembering being taught that Physics _is_ approximation.

------
zecg
I have found the perfect diet (or, rather "weight control algorithm"), have
lost about 60 pounds and haven't gained them back for a couple of years now.
The algorithm is extremely simple: "If you ate yesterday, don't eat today." It
means I fast AT LEAST half days in a year (see: alternate day fasting). On
fasting days, I drink water and green tea (with no sugar, of course). It has
numerous purported health benefits. I can vouch for weight loss, lower blood
pressure, more energy (perhaps paradoxically) and better digestion. It also
frees a lot of time, since you don't have to plan, eat, or acquire food half
the time and it turns out digestion also "needs" sleep, so I can get by with
sleeping less on days I'm empty. The only side effect is that of lower blood
pressure - I sometimes get dizzy if rising up fast from crouching. I started
doing this after fasting for 60 hours every fortnight for a year, I loved the
feeling and wanted more of it. It also makes me appreciate food much more on
the days I do eat. As disclaimer (YMMV), I tend to avoid food additives which
are known to be bad (coal tar-based paintstuffs, artificial sweeteners,
certain emulgators and such) - the lists of those are widely available. And I
try to eat whole-grain cereal products. I also keep kombucha as pets (very
clean and quite pets, fermented tea is best poo ever) and I bake my own bread
with wild yeast that has apparently managed to have aerial sex with my
kombucha scoby.

~~~
shin_lao
Careful with that kind of advice and things like "I have found the perfect
diet".

It's much safer and simpler to lose weight and improve overall health by
simply not eating crap (which is quite hard to do in a typical western
country, I agree) and having regular exercise.

------
terio
I don't think the difference in conversion efficiency between carbs and fat is
relevant in a "normal" diet. The main difference is in how they are
metabolized, and the effect they produce in the body.

I can only recommend everybody to stop loading huge amounts of carbs,
specially sugar. Go for simple unprocessed foods, like fruits, vegetables,
meat, fish, and so on.

The paleo lifestyle works just fine for me. I know it is hard to convince
other people to do it. Even when they see me eat like I do, and they have seen
the change in other people that adopted that practice, most people simply
resist the idea. Check out
[http://www.scientificamerican.com/blog/post.cfm?id=mummy-
say...](http://www.scientificamerican.com/blog/post.cfm?id=mummy-says-john-
horgan-is-wrong-abo-2011-05-19)

------
raleec
Also refuted here: <http://news.ycombinator.com/item?id=1006980>

------
chipsy
Related: I've been adding a bit of white vinegar to meals as a way to lower
the effective GI of carby foods. Seems to work pretty well.

~~~
ghshephard
Results will, apparently, vary. Your metabolism may be blessed as vinegar
reactive. Timothy Ferris used a glucose meter to try and track impact of
Vinegar on the GI, and didn't get positive results:

[http://bodezfitness.com/blog/tasso/post.cfm/post/4841/2-pre-...](http://bodezfitness.com/blog/tasso/post.cfm/post/4841/2-pre-
meal-tricks-to-control-your-blood-sugar-response-and-stay-in-fat-burning-mode)

------
auganov
I cannot comment much on thermodynamics/biochemistry as I don't know a bit
about those, but unfortunetaly it seems like this study has ommited the fact
that a high protein diet will always be more efficient in the beginning. They
should NOT have taken weightloss that occured in the first week or two (to be
on the safe side) into account.

Why? Protein-rich food tends to weight less, doesn't cause as much bloat.
Actually a very high fat diet might cause most loss in the beginning. For
example I eat a very high-carb diet,a lot of raw food that is not too calorie
dense, it bloats you a lot providing few calories at the same time. If one day
I decide to eat only ice cream (keeping ammount of calories the same) then on
the next day there will be a sudden big loss. Of course it will be gone once
back to eating what I eat before.

So when measuring efficienct of a diet you should exclude anything that
happens in the beginning because it's always very very volatile in that stage.
Especially when subjects tested ate a very different diet beforehand. You
could also go on to talk about sodium intake which affects water retention
which translates to changes in weight. That will cause a lot of fluctuation in
weight in the beginning too.

I keep a very detailed log of what I eat and my weight with CRON-o-Meter. When
I eat and drink same food for an extended period of time (and stay home all
the time) my weight loss is almost calorie-perfect, meaning that you could
convert the daily calorie deficit to grams and this is how much I would loose
on each day. Only once every 4-5 days there would be a slight "bump", but if
you look at the 7-day moving average it's virtually a straight line.

I went on vacations once and decided to binge, big time, 6000 calories a day
(really!), at the end of the day it was very unplesant, but well the food was
worth it, haha. Keep in mind that I weight 110lbs and eat around 1700 on a
normal day. The weight of my body has increased probably by around 5-6 kg, 4kg
was expected, rest was water retention etc. So the first few days back on a
diet were crazy. One the first day a loss of 1.3kg (and that is after a 2 day
fast already!). Next day 0.3kg, then 0.2 kg, 0.15kg, one day of no change and
then a sudden increase of 0.6 kg, after that it gruadually stareted to
approach the expected rate of loss (0.1kg/day).

Many people, when they begin a diet are very much like me going off a binge.
Not as dramatic of course, but similiar. In a choice of different food can
yield a big loss that won't be there long term. A lot of fad diets exploit
that fact and so do high protein diets. People often go on those diets, loose
even up to 5-10lbs purely because of eating a food that digests and affects
water retention in a different way and maybe some other factors that I don't
know of (10 would be a lot, but I guess plausible for a very fat individual).
Some get satisfied with that small loss, go back to the old diet and then we
hear about the mysterious "yo-yo effect", but in fact nothing strange has
happened. Those that last and continiue the diet will often say that the
"starvation mode" has kicked in. No, "starvation mode", the "water retention
effect" is gone (simplification). Some, after hitting the "starvation mode"
will even swtich to more calorie dense food increasing their total intake of
calories but reducing the sheer volume of food and claim to have beaten the
"starvation mode" with more calories. I even consciously use those tricks to
manipulate my weight sometimes (as there it can affect my mood :-) ).

I guess you understand by now. Unfortunately most studies fail to account for
that, so whenever I see a study that tries to prove something with a small
sample size, conducted over a short time frame I'm very very skeptical. But
then again, once your sample size and time frame get bigger controlling those
people gets hard, too hard. You have to make sure they eat the exact ammounts
of food they are supposed to eat. They sometimes give people directions like
eat one cup of this, 2 cups of that, CRAZY! You have to portion the food for
them, unless you explain what a "cup" of any given food is and make sure they
PERFECTLY understand you will have huge errors even with 100% honest people.
Accounting for bias is very tricky with those studies too, not going to work
too good. Psychological effects actually get stronger and harder to control
the longer the time frame is, so large N and a long time frame doesn't solve
the problem either. Physical activity is another thing. Some people burn 200
without noticing. There's very few people that truly have naturally "fast
metabolism", yet a big proportion of people that are thin claim to have that.
"I eat whatever I want and stay lean", yea you do eat whatever you want but
you don't want to eat much. Or they do sports. Or fidget all the time (which
some claim could even burn off 500 in extreme cases).

Do a study with each group having at least 30 people, same gender, similiar
weight, similiar height, healthy, close to no physical activity, not a
fidgeter. Portion food for them, don't let them do it themselves. Measure
everything they put in their mouth, water and multivitamin included. Weight
each day at the same time, same clothes, make sure they pee beforehand. Do
that for 3 months. Discard first 2 weeks of results. Perhaps the last 2 weeks
too (people are more likely to cheat at the end). That's a study that I might
care about, of course probably forgot about 20 other things I'd do.

I think conducting such a study would only be possible if you gathered a large
group of dieting/nutrition enthusiasts like me. Too hard otherwise. I really
sometimes wonder how they find people for those larger studies.

Getting my mom to diet was/is a BIG pain even given the fact that she was
willing to drop some weight. She was also extremely biased in a lot of things
she said even given that she probably knows more about nutrition then the
average person as I give her a lot of lectures :-). Now try that with 100
"normal" people that you probably DO NOT control on a daily basis. I know for
a fact that unless you drug those people, they are BIG enthusiasts or lock in
a cage and monitor the bias will be enormous.

I could go on talking for a very long time. The conclusion is pretty simple.
Most studies about weight loss are simply useless. There are many smart people
in the field of nutrition I'm sure, unfortunatelly it's very very hard to find
these amongst legions of incompetent people. I mostly see 2 kinds of the
incompetent. One group is those that are simply stupid/lazy/don't care. They
do a study to seem smart, probably because they need it to get some kind of a
credential. They study something that 100 people already did, change two
things, come up with a conclusion that is not too controversial so there's not
too many people questioning (when you're findings are interesting everybody is
going to point out even a slight flaw in the study, if you say what people
want to hear you might get away with a large, fundamental flaw, because you
state "the obivious" anyways). Another group of incompetent people are
something I'd call the "ideology-driven", those are scientists that will do
anything to prove their thesis. Actually I think those are a little better
than the first group of the incompetent. You see, the stupid/lazy ones, they
have almost a zero chance of comming up with anything interesting. The
ideology driven ones can actually find something interesting.

Ok, well I'm tired writing that long rant on the field of nutrition (but I
guess it applies to so many more fields of science). If you was bored enough
to read the whole thing please also keep in mind that I admittedly have no
education in that field, or any whatsoever, so everything I wrote is basically
based on my personal experience and what I read on the Internet. But I do not
think I have said anything that is far from the truth.

So as to that particular study, their reasoning might be right, but I wouldn't
use that data to substantiate it. They are honest people though as they do
explicitly say "one can't predict that the ratios will stay the same over a
long term dietbut the calculations show that the possibility of metabolic
advantage should not come as a surprise." And I'm afraid that the advantage
would wear off. Also note that I'm not saying that I know from my experience
that it does, because I have never really went long term on diet that's not
high carb, I hate low-carb stuff. I only have tons of experience with short
term effects and what I see in most studies are those short term effects that
I know a lot about.

------
hackermom
This is entirely besides the point of the study and the article, but why are
the Americans the only ones who, in terms of human energy intake/consumption,
say calorie when it should be kilocalorie? Why do they insist on being one
thousand times off? "It's easier"? From where does this come from, and why
does the rest of the world insist on being accurate?

~~~
woobar
Americans use term 'Calorie', not 'calorie'. 1 Cal = 1000 cal

<http://en.wikipedia.org/wiki/Calorie>

~~~
hackermom
...and the case-sensitive nature of this confusion is exactly the point I'm
trying to get across - people just don't know the difference. A Calorie is a
calorie! Just read the nutritional declaration on a few American food products
and you'll find an equal amount of both. MB, Mb or mb, anyone?

~~~
woobar
I've reread you original post and don't see any mention of case sensitivity.
In fact you insisted that americans use inproper unit (1000 times off), which
is not true at all.

Also, I always pay attention to food labels and never noticed any confusion.
As far as I can tell the units on Nutrition Facts label are always correct.[1]

[1]
[http://www.google.com/search?q=nutrition+label&tbm=isch](http://www.google.com/search?q=nutrition+label&tbm=isch)

------
cschneid
The other big thing that people end up missing is that most of your weight
isn't from the food you eat. That's just where the energy came from. Your
weight is oxygen / carbon / water / etc.

Also note: a giant tree doesn't dig out a giant hole where it grows in the
ground. The dirt isn't the bulk of the tree's wood.

~~~
acon
The fact that a tree builds itself out of thin air is one of my favorite
tidbits of knowledge. However, this kind of metabolism is only used by plants.
Humans, as all animals, gets their building blocks from what they eat and
drink. All the oxygen we use from the air we breathe is exhaled as carbon
dioxide.

~~~
Geee
This is actually pretty interesting point of view. In essence, you should try
to breath out all the carbon you ingest. Measuring the carbon dioxide output
would be a pretty accurate measure of the actual energy consumption in the
body.

~~~
saalweachter
I wonder if you could proxy your carbon dioxide output off of your breathing,
with some calibration? When I run, I breathe harder; am I expelling more or
less carbon dioxide per breath than when I am sitting in a chair? Counting
breaths seems pretty technically feasible.

Maybe your heartbeat could also work; that's also pretty easy to collect.

It'd be awesome to have a running total of how many calories I'm burning at
all time.

~~~
Geee
Polar heart rate monitors give you an estimate of the burned calories based on
your pulse. That can't be too accurate though, because some people have bigger
hearts which pump more blood per beat.

