The World Turned Upside Down: The Second Low-Carbohydrate Revolution (6 page)

The Obesity Epidemic

The
Obesity Epidemic

So, what did we eat during the past
thirty
or forty years? What
kind of macronutrients were in our diet? You may know this better than
our
students who probably did not attend to the problem.

3.
 
During the epidemic of
obesity and diabetes, the macronutrient that increased most was:

__ X _ Carbohydrate.

_____ Protein.

_____ Fat.

_____ All about the same. Calories
increased across the board.

Student
Performance on Question 3

Many students know at this point
where I
am coming from and there
are probably more votes for carbohydrate than if this were the first
question.
However, many people, students included, still think that calories were
increased across the board. The epidemic of obesity and diabetes has
been
accompanied by a substantial
de
crease
in the percent fat and, at least for men, the absolute amount also went
down
slightly.

Figure 2-2
shows data from the National Health and Nutrition Examination Survey
(NHANES)
which is conducted at the intervals listed in the horizontal axis. The
vertical
axis is the absolute amount of calories consumed and the large increase
in energy
consumed appears to be due entirely to a dramatic increase in the
consumption
of carbohydrate. The percent change shown along the top indicates the
expected
decrease in fat but, at least for men, the absolute amount of fat
(total
calories) and, notably, the absolute amount of saturated fat went down.

There is a lot of error in these
kinds of
surveys but it is
pretty much excluded that there was any
increase
in fat intake. It is also likely that
if obesity and
diabetes had gotten better, it would have been attributed to the
significant
fall in saturated fat consumption. The clearest conclusion is that an
increase
in carbohydrate consumption compared to fat is associated with greater
total
intake and that a "Western diet," as they call it in the nutrition
literature,
does not mean a high fat diet.

It is widely said that association
does
not imply causality. More
accurate is that association does not
necessarily
imply causality. Few people would deny that the association of dietary
calories
and body mass is causal, however non-linear the association might be.
Whether
the association between increased carbohydrate intake and increased
calories is
causative is one of the themes in this book.

Figure
2-2
. Consumption of macronutrients during the
epidemic of obesity
and diabetes. Inset: number of people with diabetes. The horizontal
axis
represents the period in which NHANES ( National Health and Nutrition
Examination Survey) collected data. The left vertical axis is the
absolute
energy input in kcal. The right axis is the % change in calories. The
ratios of
macronutrient is shown along the top.

We also ask whether the inset showing
the
carbohydrate-diabetes
association in
Figure 2-2
tells us about what causes what. The argument will be that, given the
effectiveness
of low-carbohydrate (high-fat) diets as a treatment (sometimes a
virtual cure)
for diabetes, it would be surprising if carbohydrates were not involved
in some
way in a causative role.

Finally, there is an obvious
association between the
official advice of the USDA, the AHA and just about everybody else to
reduce
fat and increase carbohydrates and what people actually did. They
reduced fat,
at least as a percentage of calories and they dramatically increased
carbohydrates.

Looking ahead, one way to test
whether
there is a causal link
between carbohydrate intake and obesity, is to simply reduce
carbohydrates and
see if total caloric intake goes down or, in fact whether diabetes
incidence
goes down. There are some good experiments that test this. The results
are as
expected and the details of one experiment are described in Chapter 9.
Whatever
else can be drawn from these data, the association between increased
carbohydrate/decreased fat and obesity and diabetes is the single
result that
makes the largest impact on our medical students and remains an
undercurrent in
any analysis of the role of macronutrients.

4.
     
The
macronutrient most likely to raise blood glucose in people with type 2
diabetes
is:

__
X
_
Carbohydrate.

_____ Protein.

_____ Fat.

_____ Alcohol.

This is, or should be obvious. The
correct
answer was chosen by
83 % of our students. The surprise is probably that anybody got it
wrong.
Diabetes is fundamentally a disease (really several diseases) of
carbohydrate
intolerance. People with type 1 diabetes cannot produce the hormone
insulin in
response to blood glucose. People with type 2 have progressive
deterioration of
the insulin-producing beta cells of the pancreas. They do produce
insulin but
their cells respond poorly. They are said to show insulin resistance.
Insulin
has effects on many tissues, particularly adipocytes (fat cells).
Diabetes is
as much a disease of fat metabolism as of carbohydrate metabolism: the
primary
effect of insulin is on synthesis and breakdown of fat and a person
with type 2
diabetes may have excessive fatty acids in their blood. Nonetheless,
the most
obvious characteristic and the major risk for other symptoms is the
hyperglycemia (high blood glucose). Different carbohydrate-containing
foods
raise blood glucose to different extents but the general principle
holds.

The dietary requirement
for carbohydrate

5.
      
The
dietary requirement for carbohydrate is:

_____ approximately 130 g/day

_____ approximately 50 % of calories

_____ as much as possible

__
X
_
there is no dietary requirement for carbohydrate

Student
Performance on Question 5

There is no requirement for dietary
carbohydrates as there is for
the so-called essential amino acids or essential fatty acids. This does
not
mean that anybody recommends doing without them altogether even if this
were
possible (even meat has a small amount of carbohydrates).

That there is no dietary requirement
for
carbohydrate means, in a
practical sense, that if do want to reduce carbohydrate, there is no
biological
limit on how
much you can restrict intake. The extent to which you actually do so
will
depend on your personal reaction and taste but you do not
need
to consume any at
all. It is always emphasized that the brain needs glucose but your body
is
capable of making glucose from protein from the process known as
gluconeogenesi
s
and supplying glucose from storage as
glycogen
.
There are also alternative
fuels in the form of
ketone
bodies
. You more or less knew this. If you
did need dietary
carbohydrate, you would die if you went without food for a week; you
store a
lot of fat but not much carbohydrate. More on glycogen and
gluconeogenesis in
Chapter 7
.

6.
      
The
amount of carbohydrate recommended by the American Diabetes Association
(ADA)
and other health agencies:

_____ approximately 130 g/day

__X_ approximately 50 % of calories

_____ as much as possible

_____ as little as possible

Student
Performance on Question 6

It is hard to believe that a diabetes
agency would
recommend
any amount of
carbohydrate but this is it. Their 2008 dietary guidelines contain the
rather
remarkable advice:

Sucrose-containing foods can
be substituted for
other carbohydrates in the meal plan or, if added to the meal plan,
covered
with insulin or other glucose-lowering medications. Care should be
taken to
avoid excess energy intake. (A)

To many people this seems to be
saying
that it is okay to make
things worse so that you can take more drugs. The (A) mark indicates
that they
consider this advice to be based on their highest level of evidence.
They don't
cite that evidence but it is surely not experimental. While this book
was being
written, the ADA quietly dropped this passage from their 2013
guidelines [10]
but have not explicitly indicated that it was wrong. It is unknown
whether the
rank and file of ADA membership ever read those statements or and, if
so,
thought that they were of high quality or simply political statements
with
which no one has time to fight.

Although brain fuel needs can be
met on lower-carbohydrate
diets, long-term metabolic effects of very low-carbohydrate diets are
unclear.

In fact, the long term effects
are
clear. Very clear – there are trials going out to one or two years, and
internet sites and forums make apparent that it is a way of life for
many
people with diabetes. Although personal stories are hard to document,
we would
know if there were any indication of long term problems. More
important,
there is no reason to suggest that there
would
be any long term effects. In science, you don't start from scratch. You
don't
assume that there is harm unless there is a reason to. Nothing in
reducing
carbohydrate suggests harm. And "unclear" implies conflicting
data.  There
is no conflicting data and no reason to expect any. I suggested to a
spokesperson for the ADA that they were stronger on what they were
opposed to
than on anything positive that they had to offer. She admitted that
that was a
fair criticism. So, why are they opposed to carbohydrate restriction?