There's a lot in the book that most LC eaters may never need
to know (pre bodybuilding contest plans which come up late
in the book), but it does a very good job at explaining the
basics of fuel systems and LC.

MEOW ! ~

But the suggestions of misreading the literature are more than a mere
catfight.

Well, there is an essential aspect called "do you know more about the
scientific method than a five year old?"

The book is a massive statement that the medical/nutrition industry is
far from scientific, as have been most of the conventional nutrition
writers.

In her book, she portrayed the massive criticism of Banting as did
Taubes. Yet, she neglected the entire role of poor quality science, I
believe.

Taubes referenced 7 of her works, but not her recent book, which may
have been too recently published to get into the slow book
publishing/printing/distributing cycle.

Taubes lists himself only twice in the bibliography.

I guess they thought Jane Brody would be just too amusing?

A calorie is not a calorie:

BioMed Central
Page 1 of 5
(page number not for citation purposes)
Nutrition Journal
Review Open Access
"A calorie is a calorie" violates the second law of thermodynamics
Richard D Feinman*1 and Eugene J Fine1,2
Address: 1Department of Biochemistry, State University of New York
Downstate Medical Center, Brooklyn, NY 11203 USA and 2Department of
Nuclear Medicine, Jacobi Medical Center, Bronx, NY 10461 USA
Email: Richard D Feinman* - rfeinman@downstate.edu; Eugene J Fine -
efine@downstate.edu
* Corresponding author
Abstract
The principle of "a calorie is a calorie," that weight change in
hypocaloric diets is independent of
macronutrient composition, is widely held in the popular and technical
literature, and is frequently
justified by appeal to the laws of thermodynamics. We review here some
aspects of
thermodynamics that bear on weight loss and the effect of macronutrient
composition. The focus
is the so-called metabolic advantage in low-carbohydrate diets – greater
weight loss compared to
isocaloric diets of different composition. Two laws of thermodynamics
are relevant to the systems
considered in nutrition and, whereas the first law is a conservation (of
energy) law, the second is
a dissipation law: something (negative entropy) is lost and therefore
balance is not to be expected
in diet interventions. Here, we propose that a misunderstanding of the
second law accounts for the
controversy about the role of macronutrient effect on weight loss and we
review some aspects of
elementary thermodynamics. We use data in the literature to show that
thermogenesis is sufficient
to predict metabolic advantage. Whereas homeostasis ensures balance
under many conditions, as
a general principle, "a calorie is a calorie" violates the second law of
thermodynamics.
Review
The recent awareness of an epidemic of obesity coincides
with, and may have contributed to a dramatic increase in
the popularity of a variety of low carbohydrate diets. This
rapid switch in dietary habits of a significant part of the
population, and the virtual revolution in the food industry,
is unusual in that it stands in direct opposition to
long-standing recommendations of the majority of the
nutritional and medical establishment (e.g. [1,2]).
Despite isolated examples, such as a recent editorial by
Walter Willet pointing to the need to understand low carbohydrate
diets [3], there is still little real acceptance by
nutrition professionals or health organizations. One
aspect of these diets that has been especially controversial
is the so-called metabolic advantage – the idea that more
weight may be lost calorie for calorie compared with diets
of higher carbohydrate content.
We recently reviewed the literature on metabolic advantage
[4]. We showed that there is a sufficient number of
reports in the literature to establish the existence of metabolic
advantage and we tabulated results from ten or so
studies demonstrating that low carbohydrate diets can
lead to greater weight loss than isocaloric low fat diets.
The reports we cited have frequently been met with the
criticism that the data could not be right because they
would violate the laws of thermodynamics ([5,6]). An
example is the recent demonstration of metabolic advantage
in a small, pilot study [7] which, despite its preliminary
status, was extremely well controlled. Three groups
were studied: A low carbohydrate group (LoCHO = 1800
Published: 28 July 2004

Nutrition Journal 2004, 3:9 doi:10.1186/1475-2891-3-9
Received: 21 April 2004
Accepted: 28 July 2004
This article is available from: http://www.nutritionj.com/content/3/1/9
© 2004 Feinman and Fine; licensee BioMed Central Ltd. This is an
open-access article distributed under the terms of the Creative Commons
Attribution
License (http://creativecommons.org/licenses/by/2.0), which permits
unrestricted use, distribution, and reproduction in any medium, provided
the original
work is properly cited.
Nutrition Journal 2004, 3:9 http://www.nutritionj.com/content/3/1/9
Page 2 of 5
(page number not for citation purposes)
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. This work received a
good deal of attention in the popular press. Media reports,
however, included comments of experts that "It doesn't
make sense, does it?" "It violates the laws of thermodynamics.
No one has ever found any miraculous metabolic
effects." ([5]). If this is an accurate quotation, it is odd
indeed. Miraculous, or otherwise, a metabolic effect was
found. In the absence of an identifiable methodological
error, experimental data has to be accepted and numerous
investigations, in fact, serve as precedents for Greene et
al.'s findings (Reviews: [4,8]).
In our previous review of metabolic advantage [4] we
showed that there is, in fact, no theoretical violation of the
laws of thermodynamics, and we provided a plausible
mechanism. In general the pathways for gluconeogenesis
that are required in order to supply obligate glucose (e.g.
to brain and CNS), in combination with increased protein
turnover, could account for the missing energy. Here, we
simplify the thermodynamic argument and review some
of the relevant principles. We show, moreover, that wellestablished
data in the traditional nutritional literature
predict metabolic advantage and no one should be surprised.
The ironic conclusion is that the principle that
weight gain on isocaloric diets must always be independent
of macronutrient composition would violate the second
law of thermodynamics.
What do we mean by "a calorie is a calorie?"
Because it is a colloquial phrase, it is important to understand
exactly what it is meant by "a calorie is a calorie."
The most common meaning is that is it impossible for two
isocaloric diets to lead to different weight loss. Frequently,
the concept is justified by reference to the "laws of thermodynamics",
but an explicit connection has never been
spelled out. More recently, Buchholz & Schoeller [10]
appear to identify "a calorie is a calorie" with the first law
of thermodynamics. They also admit that high protein /
low carbohydrate diets can lead to greater weight loss than
isocaloric low fat diets in agreement with our assessment
[4]. Nonetheless they maintain that "a calorie is a calorie,"
now justifying it by their connection of the phrase to the
concept of energy conservation. It is important to point
out that no study of isocaloric diets has ever claimed that
the first law of thermodynamics is not true. Buchholz &
Schoeller [10] have limited themselves by only including
the first law and, therefore, do not understand how the
differential weight loss could occur and think it "deserves
further study." Our major point here is that there is more
than one law of thermodynamics and that a more accurate
understanding of the role of the second law shows that
differential weight loss is not inconsistent with any physical
principle.
Thermodynamics
The idea that "a calorie is a calorie" comes from a misunderstanding
of the laws of thermodynamics. There are two
laws of thermodynamics. (The zeroth law that establishes
the concept of temperature and the third law that
describes absolute zero are not relevant here). When
speaking of "the laws of thermodynamics" it is important
to be sure that one is including the second law. The first
law is very different in character from the second law
[9,11,12]. The first law is a conservation law: it says that
the form of energy may change, but the total is always
conserved. The second law is a dissipation law: it defines a
quantity, the entropy, S, which we traditionally identify
with disorder or high probability. The second law says
that in any (real) irreversible process, the entropy must
increase (ΔS > 0); balance is not expected. Entropy is, in
fact, identifiable with irreversibility.
It is important to understand that it is the second law that
drives chemical reactions. The first law is a bookkeeping
law and tells us that the total energy attributed to work,
heat and changes in chemical composition will be constant.
It does not tell us whether such a reaction will occur,
or if it does, what the relative distributions of the forms of
energy will be. To predict the tendency of the reaction to
occur, we must employ the second law that says the
entropy must increase. In a chemical reaction, at constant
temperature and pressure, the entropic and energetic
effects are combined into the change in the Gibbs free
energy, ΔG, whose sign predicts the direction of reaction,
and whose magnitude indicates the maximum amount of
work realizable from the reaction.
PFaigthuwreay 1s for oxidation of macronutrients
Pathways for oxidation of macronutrients.
Nutrition Journal 2004, 3:9 http://www.nutritionj.com/content/3/1/9
Page 3 of 5
(page number not for citation purposes)
Application of ΔG'
To understand the implications of "a calorie is a calorie,"
that energy yield could be path-independent and the same
for all diets consider that it implies that carbohydrate and
protein are equivalent fuels as shown in Figure 1. The diagram
indicates that, because it is a state variable, the free
energy (ΔG') for Path 1 must be equal to that for path 2 +
3. If the ΔG' values for path 1 and path 2 are taken to be
their calorimeter values, they will be approximately equal
(~4 kcal/g, path 1 corrected for ureagenesis). This means
that ΔG' for path 3, the conversion of protein to carbohydrate
(also corrected) must be about zero. There exists at
least one condition where this is not true, the standard
state; it is generally considered that gluconeogenesis from
one mole of alanine requires about 6 ATP [13,14]. Of
course free energies are concentration dependent, so in
vivo values will differ from standard state values but they
are continuous functions of the concentrations and there
will be numerous conditions under which ΔG' is not zero.
In other words, assuming that protein and carbohydrate
are energetically equivalent leads to a contradiction.
Inefficiency
The second law was developed in the context of the industrial
revolution and the attempt to understand the efficiency
of machines. The law describes the theoretical
limits on the efficiency of engines and applies as well to
living (irreversible) systems. The second law says that no
machine is completely efficient. Some of the available
energy is lost as heat and in the internal rearrangement of
chemical compounds and other changes in entropy. In
other words, although the first law holds even in irreversible
processes – energy is still conserved – the second law
says that something is lost, something is unrecoverable.
The efficiency of a machine is dependent on how the
machine works and, for a biochemical machine, the
nature of the fuel and the processes enlisted by the organism.
A simple example is the inefficiency of low-test gasoline
in high compression gasoline engines. If a "calorie is
a calorie" were true, nobody would pay extra for high test
gasoline. (The calorimeter values of a gasoline will be the
same whether or not it contains an antiknock compound).
In weight loss diets, of course, inefficiency is
desirable and is tied to hormonal levels and enzyme
activities
TFhigeu dreep 2endence of effective calories on % carbohydrate in a 2000
kcal diet
The dependence of effective calories on % carbohydrate in a 2000 kcal
diet. Effective calories were determined by subtracting
the losses due to thermogenesis as described in the text.
Nutrition Journal 2004, 3:9 http://www.nutritionj.com/content/3/1/9
Page 4 of 5
(page number not for citation purposes)
Efficiency and thermogenesis
In nutrition, one component of inefficiency is measured
in thermogenesis (thermic effect of feeding), or the heat
generated in processing food. There is a large literature on
this subject and the general conclusion, as summarized in
a recent review by Jéquier [15], is that thermic effects of
nutrients is approximately 2–3 % for lipids, 6–8 % for carbohydrates,
and 25–30% for proteins. It is interesting that
this data itself might be enough to explain metabolic
advantage. Here we took the average of Jéquier's values
(2.5, 7 and 27.5 % for fat, CHO and protein) and calculated
the effective energy yield for a 2000 kcal diet. If we
assume a diet composition of CHO:fat: protein of
55:30:15, within the range of commonly recommended
diets, the calculated effective yield is 1848 kcal. We now
consider the effect of reducing carbohydrate progressively
and substituting the calories removed equally between fat
and protein. Figure 2 shows that the wasted calories due
to thermogenesis increase as carbohydrate is reduced and
reach 100 kcal at 21 % carbohydrate. This value of 100
kcal is recommended by several professionals as the goal
for daily weight reduction (e.g. [16]). Notably, at 8 %
CHO, the value for the early phase of the Atkins [17],
South Beach [18] or Protein Power diets [19], 140 kcalories
are lost as heat. Now, there will be metabolic accommodations
and one can't predict that the ratios will stay
the same over a long term diet, but the calculations show
that the possibility of metabolic advantage should not
come as a surprise.
Recommendations for fighting obesity frequently call for
small reductions in calories [16]. In fact, given the resistance
of steady state systems to small perturbations it is
doubtful that this is a promising strategy. Nonetheless,
taking the goal at face value, if it could be achieved by a
simple change in macronutrient composition, such a
method would seem worthy of serious consideration. The
arguments above show that such a phenomenon is possible.
There are plausible arguments for how it could take
place and substantial experimental evidence for its occurrence
[4].
Conclusions
A review of simple thermodynamic principles shows that
weight change on isocaloric diets is not expected to be
independent of path (metabolism of macronutrients) and
indeed such a general principle would be a violation of
the second law. Homeostatic mechanisms are able to
insure that, a good deal of the time, weight does not fluctuate
much with changes in diet – this might be said to be
the true "miraculous metabolic effect" – but it is subject to
many exceptions. The idea that this is theoretically required
in all cases is mistakenly based on equilibrium, reversible
conditions that do not hold for living organisms and an
insufficient appreciation of the second law. The second
law of thermodynamics says that variation of efficiency
for different metabolic pathways is to be expected. Thus,
ironically the dictum that a "calorie is a calorie" violates the
second law of thermodynamics, as a matter of principle.
The analysis above might be said to be over-kill although
it is important, intellectually, not to invoke the laws of
thermodynamics inappropriately. There are also, however,
practical consequences. The seriousness of the
obesity epidemic suggests that we attack it with all the
means at our disposal. Metabolic advantage with low carbohydrate
diets is well established in the literature. It does
not always occur but the important point is that it can
occur. To ignore its possibilities and to not investigate the
precise conditions under which it appears would be cutting
ourselves off from potential benefit. The extent to
which metabolic advantage will have significant impact in
treating obesity is unknown and it is widely said in studies
of low carbohydrate diets that "more work needs to be
done." However, if the misconception is perpetuated that
there is a violation of physical laws, that work will not be
done, and if done, will go unpublished due to editorial
resistance. Attacking the obesity epidemic will involve giving
up many old ideas that have not been productive. "A
calorie is a calorie" might be a good place to start.
Competing interests
None declared.
References
1. Saltos E: The Food Pyramid-Food Label Connection. [http://
vm.cfsan.fda.gov/~dms/fdpyrmid.html].
2. American Heart Association guidelines for weight management
programs for healthy adults. AHA Nutrition
Committee. Heart Dis Stroke 1994, 3:221-228.
3. Willett WC: Reduced-carbohydrate diets: no roll in weight
management? Ann Intern Med 2004, 140:836-837.
4. Feinman RD, Fine EJ: Thermodynamics and Metabolic Advantage
of Weight Loss Diets. Metabolic Syndrome and Related
Disorders 2003, 1:209-219.
5. Rolls BJ: . quoted in October 13, 2003 CBS News [http://
www.cbsnews.com/stories/2003/02/15/health/main540776shtml] .
6. Bray GA: Low-Carbohydrate Diets and Realities of Weight
Loss. JAMA 2003, 289:1853-1855.
7. Greene P, Willett W, Devecis J, A. Skaf: Pilot 12-week feeding
weight-loss comparison: Low-fat vs. low-carbohydrate
(ketogenic) diets. Obesity Research 2003, 11:A23.
8. Westman EC, Mavropoulos J, Yancy WS, Volek JS: A Review of
Low-carbohydrate Ketogenic Diets. Curr Atheroscler Rep 2003,
5:476-483.
9. Kondepudi D, Prigogine I: Modern Thermodynamics. From
Heat Engines to Dissipative Structures. Chichester, John Wiley
& Sons; 1998.
10. Buchholz AC, Schoeller DA: Is a calorie a calorie? Volume 79. Am
J Clin Nutr; 2004:8995-9065.
11. Caplan S. Roy, Essig A: Bioenergetics and linear nonequilibrium
thermodynamics. The steady state. Cambridge, MA, Harvard
University Press; 1983.
12. Carter W. Craig: About Thermodynamics. [http://pruffle.mit.edu/
300/Syllabus_web/node5html] 2002.
13. Voet D, Voet JG: Fundamentals of Biochemistry. 3rd edition.
New York, John Wiley & Sons; 2004.
14. Devlin TM: Textbook of Biochemistry with Clinical
Correlations. Fifth edition. New York, John Wiley Sons, Inc.; 2002.
Publish with BioMed Central and every
scientist can read your work free of charge
"BioMed Central will be the most significant development for
disseminating the results of biomedical research in our lifetime."
Sir Paul Nurse, Cancer Research UK
Your research papers will be:
available free of charge to the entire biomedical community
peer reviewed and published immediately upon acceptance
cited in PubMed and archived on PubMed Central
yours — you keep the copyright
Submit your manuscript here:
http://www.biomedcentral.com/info/publishing_adv.asp
BioMedcentral
Nutrition Journal 2004, 3:9 http://www.nutritionj.com/content/3/1/9
Page 5 of 5
(page number not for citation purposes)
15. Jequier E: Pathways to obesity. Int J Obes Relat Metab Disord 2002,
26 Suppl 2:S12-7.
16. Hill JO, Wyatt HR, Reed GW, Peters JC: Obesity and the environment:
where do we go from here? Science 2003, 299:853-855.
17. Atkins RC: Dr. Atkins' New Diet Revolution. New York, Avon
Books; 2002.
18. Agatston A: The South Beach Diet. New York, Random House;
2003.
19. Eades MR, Eades MD: Protein Power. New York, Bantam Books;
1996.