The World Turned Upside Down: The Second Low-Carbohydrate Revolution by Richard David Feinman
Authors: Richard David Feinman
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saturated fat → unsaturated fat
Answers
The calorie. The
calorimeter.
1. The most energy dense food
(most calories/gram) is:
_____ Carbohydrate.
_ X __ Fat.
_____ Protein.
_____ Alcohol.
Student
Performance on Question
1 .
Our first year medical students do
surprisingly poorly
considering that question is so basic. Typically only 80 % of our
incoming
class gets this right. Although they have not yet been through the
metabolism
course, this is a very highly educated group of people and we had
assumed that
everybody knew that fat was the most energy dense macronutrient. The
explanation, which contains some information, is that they were not
curious
about nutrition because they didn't see it as part of medicine and
because they
are mostly young, healthy and thin.
Figure
2-1 . Modern Calorimeter
The operational numbers in
kilocalories/gram are 4, 4, 9
and 7 for carbohydrate, protein, fat and alcohol. Calories are a
measure of
energy. The definition of energy in physics is not too different from
the
common idea, it is a measure of the ability to do work. Heat is one
form of
energy and the calorie is defined in terms of the amount of heat
required to
raise the temperature of water one degree. Note that the dietary
"calorie" is
equal to a physical kilocalorie (kcal), that is, 1000 physical
calories. Use of
"kcal" in nutrition is increasing and in this book we use kcal when
actually
referring to the quantity. It is one small step to help nutrition
become
scientific. The calories in food are measured in a device known as a
calorimeter. Food is placed in a small container in an atmosphere of
oxygen
under pressure and then ignited. By measuring the amount of heat
generated from
the change in temperature in the water bath, we can determine the
energy for
oxidation which can be assigned to the food. This is the real
definition of the
nutritional calorie. It all looks obvious but there are a couple of
very
important points:
The calories assigned to a food
represents
the energy for
complete combustion of that food in oxygen. Calories refers to a
chemical
reaction (not to the food):
Food + oxygen → carbon dioxide + water
Food + O 2 → CO 2 + H 2 O
(said: "food plus oxygen goes to
CO-two and water").
Heat produced in the calorimeter
measures
the energy for the
specific reaction .
Again, the energy is in the reaction, not
in the food . It is not like particle physics
where the mass of a
particle is given in electron-Volts, a unit of energy (because of E = mc 2 ).
We will come back to this point when we consider what is wrong with the
idea
that a "calorie is a calorie," that the amount of weight you gain or
lose on a
diet depends only on how many calories without regard to the specific
food. It
will turn out that the composition of the food is important because,
again, the
calories associated with a food is the energy obtained in the course of
complete
combustion of that food as measured in the calorimeter. If you do
anything
else, make protein, make DNA, make any kind of new cell material, then
the
calorimeter value does not apply.
Fat is the most energy dense
macronutrient
at 9 kcal/g and, for that
reason, it is considered inherently fattening by nutritionists. This is
the
basis of traditional recommendations for low-fat diets for obesity. But
there
is more to the problem than caloric density. And, it turns out that
there is
more to getting fat than total calories. To see how this all plays out
in a
real situation, consider the next question.
2. For a slice of buttered bread,
which is
more fattening?
_____ The butter.
_____ The bread.
_____ Both are equally fattening.
__ X_ Cannot tell from the
information
given.
Student
Performance on Question 2
aa
This is a trick question. It doesn't
really have an answer, that
is "you cannot tell" is the answer. An argument could be made that 9
kcal/g is
inherently more fattening but you really need more information. If you
put a
lot of butter on the bread
Answers
The calorie. The
calorimeter.
1. The most energy dense food
(most calories/gram) is:
_____ Carbohydrate.
_ X __ Fat.
_____ Protein.
_____ Alcohol.
Student
Performance on Question
1 .
Our first year medical students do
surprisingly poorly
considering that question is so basic. Typically only 80 % of our
incoming
class gets this right. Although they have not yet been through the
metabolism
course, this is a very highly educated group of people and we had
assumed that
everybody knew that fat was the most energy dense macronutrient. The
explanation, which contains some information, is that they were not
curious
about nutrition because they didn't see it as part of medicine and
because they
are mostly young, healthy and thin.
Figure
2-1 . Modern Calorimeter
The operational numbers in
kilocalories/gram are 4, 4, 9
and 7 for carbohydrate, protein, fat and alcohol. Calories are a
measure of
energy. The definition of energy in physics is not too different from
the
common idea, it is a measure of the ability to do work. Heat is one
form of
energy and the calorie is defined in terms of the amount of heat
required to
raise the temperature of water one degree. Note that the dietary
"calorie" is
equal to a physical kilocalorie (kcal), that is, 1000 physical
calories. Use of
"kcal" in nutrition is increasing and in this book we use kcal when
actually
referring to the quantity. It is one small step to help nutrition
become
scientific. The calories in food are measured in a device known as a
calorimeter. Food is placed in a small container in an atmosphere of
oxygen
under pressure and then ignited. By measuring the amount of heat
generated from
the change in temperature in the water bath, we can determine the
energy for
oxidation which can be assigned to the food. This is the real
definition of the
nutritional calorie. It all looks obvious but there are a couple of
very
important points:
The calories assigned to a food
represents
the energy for
complete combustion of that food in oxygen. Calories refers to a
chemical
reaction (not to the food):
Food + oxygen → carbon dioxide + water
Food + O 2 → CO 2 + H 2 O
(said: "food plus oxygen goes to
CO-two and water").
Heat produced in the calorimeter
measures
the energy for the
specific reaction .
Again, the energy is in the reaction, not
in the food . It is not like particle physics
where the mass of a
particle is given in electron-Volts, a unit of energy (because of E = mc 2 ).
We will come back to this point when we consider what is wrong with the
idea
that a "calorie is a calorie," that the amount of weight you gain or
lose on a
diet depends only on how many calories without regard to the specific
food. It
will turn out that the composition of the food is important because,
again, the
calories associated with a food is the energy obtained in the course of
complete
combustion of that food as measured in the calorimeter. If you do
anything
else, make protein, make DNA, make any kind of new cell material, then
the
calorimeter value does not apply.
Fat is the most energy dense
macronutrient
at 9 kcal/g and, for that
reason, it is considered inherently fattening by nutritionists. This is
the
basis of traditional recommendations for low-fat diets for obesity. But
there
is more to the problem than caloric density. And, it turns out that
there is
more to getting fat than total calories. To see how this all plays out
in a
real situation, consider the next question.
2. For a slice of buttered bread,
which is
more fattening?
_____ The butter.
_____ The bread.
_____ Both are equally fattening.
__ X_ Cannot tell from the
information
given.
Student
Performance on Question 2
aa
This is a trick question. It doesn't
really have an answer, that
is "you cannot tell" is the answer. An argument could be made that 9
kcal/g is
inherently more fattening but you really need more information. If you
put a
lot of butter on the bread
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