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A calorie is a calorie violates the second law of thermodynamics'

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Title: A calorie is a calorie violates the second law of thermodynamics'


1
A calorie is a calorie violates the second law
of thermodynamics.
When is a calorie a calorie? A thermodynamical
treatment of dietary macronutrient composition
Richard D Feinman, Eugene J Fine.
Nutritional Journal 2004 39.
Mike Wininger. Rutgers BME. 9november2004.
2
abstract.
The success of popular diets (Atkins, for
example) is based on the principle that an
isocaloric intake of variable macronutrient
composition will generate variable weight loss as
a function of underlying metabolic advantages.
Carbohydrates metabolically disadvantageous. Fats
Proteins more conducive to weight loss.
But common sense suggests that a calorie is a
calorie. A calorie of carbohydrates should be
equally contributory to weight gain and loss as a
calorie of fat or protein.
3
nutritional principles.
The human diet is composed of 3 macronutrient
elements
  • Carbohydrates A low-carb diet features less than
    50 of dietary in-take from carbohydrates 1
  • Fats Intake not to exceed 30 2
  • Proteins Intake not to exceed 20 2

-Abbreviate carbohydrates, fats, and proteins
herewith as (CFP)
McGovern Select Committee on Nutrition and Human
Needs (583012)13 Professional Distance
Runner (701020)14 Arnold Schwarzenegger
(late 1970s) (402040) 13
4
nutritional principles.
  • Body consumes macronutrients in quantities in
    excess of physiological need
  • What is not used is stored as fat
  • Energy expenditure funded by carbs first, then
    fats and proteins (in parallel) 3
  • When carbohydrate reserves run out, metabolic
    pathways reroute to utilize fat stores
  • The principle behind low-carb regimens is that
    without these carbohydrate reserves
  • to interfere, we eliminate the middle-man,
    and fat will be the immediate fuel source.

5
nutritional principles.
The Gibbs free energy is defined as the enthalpy
(internal energy) of the system minus the product
of the temperature times the entropy (energy
which can not be used to do work) of the system.
G H (TS)
  • G is a state function
  • Either calculated as a function of
    product/reactant concentrations (?G-RT ln K
    Kproducts/reactants or measured empirically
    via a calorimeter
  • In a dynamic system we rewrite

?G ?H - T?S
6
nutritional principles.
Caloric value measured in terms of kCalories,
equates to ?G
?
Food O2 CO2 H20
A quantity of food is represented by its caloric
values
1gCHO4kCal 1gFat9kCal 1gProtein4kCal
Values instituted by USDA-regulated foods and
restaurant foods 2.
…Which spurs the argument that a calorie is a
calorie a protein-rich diet is the same as a
carbohydrate-rich diet.
7
metabolism.
  • ATP is the energy currency of the body.
  • The goal is to ingest food, metabolize it into
    energy
  • Some macronutrients produce ATP easier than others

8
carbohydrate metabolism.
  • Glucose is broken down into pyruvate by
    glycolysis.
  • Pyruvate becomes Acetyl CoA, joins in the Citric
    Acid cycle to generate ATP.
  • Most of the metabolic energy derived from glucose
    comes from the entry of pyruvate into the CAC and
    oxidative phosphorylation (aerobic).

9
fat metabolism.
  • Fat metabolism is performed by ?-oxidation,
  • degrades the carbon chain 2 carbons at a time,
    releasing
  • 1 Acyl CoA shortened by 2 carbons
  • 1 Acetyl CoA
  • 1 FADH2
  • 1 NADH
  • Acetyl CoA goes into Citric Acid Cycle
  • Each molecule that goes through
  • the CAC generates 10ATP
  • FADH2 and NADH go enter oxidative
  • phosphorylation

10
protein metabolism.
  • Proteins are cleaved into their composites an
    ?-amino group and a carbon skeleton
  • Skeletons are degraded to precursors used in
    biosynthetic reactions
  • The C-3 family of amino acids forms pyruvate (CAC
    precursor)
  • In the absence of glucose, amino acids can form
    CAC intermediates
  • KWASHIORKOR.
  • Insufficient protein intake under otherwise
    normal caloric conditions. Characterised by
    edems, fragile hair and skin, reduced healing of
    wounds, depressed cellular immune function.
    Common in underdeveloped countries and can happen
    in nursing homes or hospitals where insufficient
    attention has been paid to nutritional
    considerations. 3

Figure Effect of path on the energetics of
oxidation 1
11
gluconeogenesis.
  • The purpose of gluconeogenesis is to synthesize
    glucose from non-carbohydrate precursors.
  • Pyruvate carboxylase, a biotin containing enzyme,
    catalyzes a key reaction in the mitochondria.
  • The enzyme glucose 6-phosphatase is found in the
    liver and key to the release of glucose
  • Alanine and pyruvate are used gluconeogenesis in
    liver

12
protein as a substitute.
All functions can be sustained on a low
carbohydrate in-take, but adjustments must be made
For instance, on a low-carb diet, there may be
insufficient glucose to form citrate, but amino
acid residues can jump in as succinyl-coA
Figure See B/L 40-4
13
outlaws?
Proponents of the low-carb diet suggest that they
provide a metabolic advantage.
Low carbohydrates moderate weight loss High
protein maximal weight loss..
And there is experimental precedent to support
the claims….
Volek, Westman Very Low Carbohydrate weight-loss
revisited Cleve Clin J Med, 200269,
Baba, Sawaya, etal High Protein vs High
Carbohydrate Int J Obes Relat Metab Disorders
199923
Westman, Yancy, etal Effect of a 6-month
adherence to a low carbohydrate diet program Am J
Med 2002113
But the pundits say all calories are created
equal!!
14
first law of thermodynamics.
Energy in a closed system is conserved
EinEout
Einstein energy is proportional to mass
Energy ? mass
  • Energy that does get used will be converted to
    mass and stored as fat.
  • Weight loss principle Energy expenditure gt
    Energy in-take

Ein-Eoutnet weight gain/loss 2000kCal-2100kCal-1
00kCal
15
ceteris paribus.
  • Healthiest, most direct means of weight loss is
    exercise.
  • But this precedent of low-carb weight loss has
    been demonstrated in experiments where activity
    levels have been tightly controlled,
  • advantage is internal, intrinsic and completely
    metabolic.

Samaha, 20035 6months weight loss(kg) (n132)
Low Carb 5.8, High Carb 1.9
Lean, 19976 6months weight loss (kg) (n46)
Low Carb 7.7, High Carb 4.7
Young, 19717 9weeks weight loss (kg) (n8)
Low Carb 16.2, High Carb 11.9
Figure Summary of Studies on Isocaloric Reducing
diets 4
16
so what does Feinman propose?
  • First law is important, but dont ignore the 2nd
    law
  • Difference between macronutrients is in the
    pathways and metabolic cycles.
  • A calorie is a calorie until it needs to be
    processed for utilization or storage.
  • Macronutrient effects on thermogenesis show a
    greater effect of protein compared to
    carbohydrate and fat.
  • Rationale Thermogenesis makes protein turnover
    energetically inefficient and thus more
    expensive

17
thermogenesis.
Define Thermogenesis (the thermic effect of
feeding). -Refers to the heat generated in
digestion and metabolism after feeding.
widely variable
60-70
  • 90-95 of ingested calories are available for
    oxidation or storage
  • Depending on lifestyle, Task-Labor can require
    between 0 and 70 of total metabolic output
  • We consider fixed-activity subjects here
  • Thermogenesis accounts for up to 15 of total
    energy expenditure 3

5-15
20-30
Figure The energy distribution of caloric intake
3
18
second law of thermodynamics.
A process at maximum- can be 100 efficient
  • Define a change in energy dE, relating to heat
    change, dQ, and change in work dW

dE dQ dW.
  • For a reversible process, in we may rewrite work
    in terms of pressure, volume, temperature and
    entropy
  • dE TdS PdV.
  • where T is the temperature, dS the entropy
    change, P the pressure, and dV volume change.

19
second law in chemodynamics.
  • The two-term expression applies to closed
    systems, close to equilibrium, with no chemical
    interactions.
  • Need a viable approximation in living organisms
    accounting for chemical reactions- change in
    quantity by moles, ni over a chemical potential
    ?i

?i
  • Thus, our 2nd law becomes

?E T?S - p?V ??i?ni
dE TdS PdV
20
?G non-zero by inspection.
  • That energy yield could be path-independent over
    isocaloric diets implies that protein and
    carbohydrates are energy equivalents.
  • (?G) for Path 1 must equal
  • (?G) Path 2 (?G) Path 3.

Figure Pathways for oxidation of macronutrients
  • However this is not so in the standard state
    gluconeogenesis from 1mol Alanine requires about
    6ATP (?Go180 kJ?0).

Figure Gluconeogenesis
21
?G non-zero by contradiction.
  • So ?G ? 0 standard state,
  • but what about at physiological conditions?
  • Show (by contradiction) that ?G 0 is not
    possible for a meaningful set of physiological
    conditions.
  • By inspection we see that ?G is constant and
    monotonically decreasing.

Note In vivo, the values are subject to change
according to body conditions, but bears no
consequence on function behavior, only on
magnitude.
Figure ?G Gibbs Free Energy is a monotonically
decreasing function for all ratios of
productsreactants
22
?G non-zero by contradiction.
So ?G is a monotonic and constant function with a
non-negative derivative. Thus we can conclude
that there exist multiple values of K for which
?G-RT ln K
is non-zero.
Proof Suppose not. Suppose that there were
multiple values of K for which ?G was zero at
constant physiological conditions. ie for K1 ?
K2, suppose ?G held a 0-value,
?G(K1) ?G(K2) RT ln K1 RT ln K2 0.
(1)
But, ?G-RT ln K is a monotonic and constant
function. Therefore in order for (1) to be true,
without a change in sign of the derivative, and
under constraint of constancy, K1 must equate to
K2, violating our supposition K1 ? K2. Thus there
are many non-zero values for ?G. In fact, there
can be at maximum one value for which ?G0.
23
synthesis.
  • 1st law of thermodynamics work is a conservative
    force, work done is path-independent
  • Path 1 Path 2 Path 3 ?G3 0
    contradiction

Equal work equal efficiency
high-carb low-carb (weight loss applications)
24
synthesis.
But we have shown ?G to be non-zero in most
instances, so we see that work done is not
path-independent.
  • Thus, proteins and carbohydrates are not
    identical energetic revenues,
  • There exists an efficiency gradient
  • Protein metabolism is a more inefficient process

…so where does the difference lie?
25
the genesis is the exodus.
  • Protein metabolism inefficiency lies in the
    thermogenesis
  • All macronutrients produce some heat in their
    metabolism, protein happens to produce much more
    than carbs or fat
  • 200kCal bolus requires 6kCal of processing avg
    macronutrient distribution
  • 3 inefficient, so a calorie is .97calorie
  • 200kCal bolus requires 6kCal of processing high
    protein composition
  • 6-8 inefficient, so a calorie is .93calorie

26
thermogenic effects.
  • Low-carb diet makes demands on protein turnover
    for gluconeogenesis.

Effects of macronutrients on Thermogenesis data
from Karst 8.
2MJ Starch 268mL/min to 279mL/min
2MJ Protein 278mL/min to 353mL/min
Ratio O2 consumption before, after meal
(ProteinStarch) 278/2681.0373
353/2791.2652
1.2652/1.03731.2197
So isocaloric ratio of Oxygen utilization is
1.22x greater for protein than for carbohydrates.
Figure Data from Karst 9. Indirect Calorimetry
data over 6h.
27
protein inefficiency.
1.54 kcal/g
3.68 kcal/g
1.32 kcal/g
Figure Effect of path on the energetics of
oxidation 1
1 kcal/g
3.45 kcal/g
1.46 kcal/g
inefficiency 6.2
inefficiency 18.2
inefficiency 5.3
28
for example.
Jequier 7 proposes a more drastic thermic
effect
7 Carbs, 2.5Lipids, 27.5Protein
  • Setup a macronutrient distribution vector
    (defined as CHOfatprotein) and a thermic
    effect vector (defined above)
  • Take dot-product to generate the inefficiency
    factor.

(.55, .30, .15?.07, .025, .275)
(0.0385 0.0075 0.0413) 0.0872.
  • Taking the difference of this factor from a
    thermally perfect operation, (with 100
    efficiency, represented by the unit 1), net
    caloric balance is

2000kCal(1-.0872)1826kCal.
29
but, MIKE!!!.
…that figure doesnt agree with MY PAPER!
Youre, right. It doesnt agree with the paper.
Richard Feinman miscalculated. In order to
generate the printed value, youd have to switch
the efficiencies
7 Carbs, 2.5Lipids, 27.5Protein 2.5 Carbs,
7Lipids, 27.5Protein
…which will generate the following net caloric
in-take
(.55, .30, .15?.025, .07, .275) (0.0138
0.0210 0.0413) 0.0761.
2000kCal(1-.0761) 1848 kCal.
So, Feinman actually misrepresented his data, but
to his detriment. Had he calculated without
error, he would have generated the mathematically
valid (and thermodynamically LESS EFFICIENT ie-
more favorable) outcome.
30
model.
Using the correct Jequier figures we generate the
following simulations comparing isocaloric diets
of variable CHOProtein (left) and
CHOProteinFat composition (right).
Figure Resultant caloric intake for variable
CHOProtein with 28, 32, 36, and 40 of calories
from fat.
Figure Resultant caloric intake, variable
CHOProteinFat, note that efficiencies bear
greatest weight at lowest carb in-take
31
conclusion.
  • By simple mathematical reasoning and empirical
    evidence, we can conclude that there is a
    metabolic advantage in a protein-rich diet.
  • Feinman produces a lucid argument that a calorie
    is a calorie violates the second law of
    thermodynamics.
  • Different macronutrients are characterized by
    different efficiencies as a consequence of their
    intrinsic metabolic pathways.

Thus, it is evident, that a calorie is indeed
not a calorie, but merely a fraction thereof,
and a differing fraction depending on
macronutrient content.
32
reality check.
The premise is attractive because the CAC is the
primary site for fat metabolism and because
glucose is usually needed to replenish the
intermediates in the TCA cycle, if carbohydrates
are restricted in the diet, dietary fat should
merely be converted to ketone bodies and
excreted. This diet appears to work at first
because low-carb diets result in initial water
(weight) loss. Glycogen reserves are depleted by
the diet, and 3g of water of hydration are lost
for every gram of glycogen. The rationale is
problematic for two immediate reasons first,
ketone body excretion by the human body usually
does not exceed 20g per day. Second, amino acids
can function effectively to replenish the CAC
intermediates, making the reduced carb regimen
irrelevant.9
33
ketosis.
The premise is attractive because the CAC is the
primary site for fat metabolism and because
glucose is usually needed to replenish the
intermediates in the TCA cycle, if carbohydrates
are restricted in the diet, dietary fat should
merely be converted to ketone bodies and
excreted. This diet appears to work at first
because low-carb diets result in initial water
(weight) loss. Glycogen reserves are depleted by
the diet, and 3g of water of hydration are lost
for every gram of glycogen. The rationale is
problematic for two immediate reasons first,
ketone body excretion by the human body usually
does not exceed 20g per day. Second, amino acids
can function effectively to replenish the CAC
intermediates, making the reduced carb regimen
irrelevant.9
34
ketosis.
  • Following a high-protein / low carb diet is not
    safe for the body to metabolize and burn fat.
  • Ketosis is the result of carbohydrate
    deprivation. Your body requires adequate amounts
    of carbohydrates in order to properly metabolize
    body fat. As the saying goes, "fat is burned in
    the furnace of carbohydrate."
  • Ketosis characterized by the appearance of
    ketone bodies. Ketone bodies are the product of
    the incomplete burning of fats. Ketones can be
    used in place of glycogen for energy production
    but they are not nearly as efficient in fueling
    exercise as glycogen.
  • Prolonged ketosis sluggishness, dehydration,
    water-weight loss, not fat loss.
  • In the absence of carbohydrates metabolism is
    predicated increasingly on amino acids (protein)
    for additional energy. This is highly
    counterproductive for anyone trying to build or
    maintain muscle mass. Loss of muscle mass means
    fewer calories burned, a decrease in metabolism
    and obvious fat gain. (from Schwarzenegger
    The Modern Bodybuilding Encyclopedia)

35
citations.
  • Feinman, R, Fine, E Thermodynamics and Metabolic
    Advantage of Weight loss. Metabolic syndrome and
    related disorders 13, 3November2003.
  • USDA Dietary Guidelines
  • Physiology Berne Levy 5/e
  • Michaelsen, KF Are There Negative Effects of an
    Excessive Protein Intake?
  • Samaha FF et al. A low-carbohydrate as compared
    with a low-fat diet in severe obesity. N Engl J
    Med 2003,348.
  • Lean, ME et al. Weight loss with high and low
    carbohydrate 1200 kCal diets in free living
    women. Eur J Clin Nutr 1997 51.
  • Young, CM et.al. Effect of body composition and
    other parameters in obese young men of
    carbohydrate level of reduction diet. Am J Clin
    Nutr 1971 24.
  • Karst H et al. Diet-Induced thermogenesis in man
    thermic effects of single proteins, carbohydrates
    and fats depending on their energy amount. Ann
    Nutr Metab 198428.
  • Biochemistry, Garret Grisham 3/e.
  • James O. Hill, Holly R. Wyatt, George W. Reed,
    John C. Peters Obesity and the Environment Where
    Do We Go from Here? Science, Vol 299, Issue 5608,
    853-855, 7 February 2003
  • Feinman, R, Fine, E A Calorie is a Calorie
    violates the 2nd law of thermodynamics. Nutrition
    Journal, 39, 28July2004
  • Karst H et al. Diet-Induced thermogenesis in man
    thermic effects of single proteins, carbohydrates
    and fats depending on their energy amount. Ann
    Nutr Metab 198428.
  • The Encyclopedia of Modern Bodybuilding,
    Schwarzenegger, Simon/Schuster 2/e
  • Runners World, August 2004
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