summarize: Dietary restriction (DR) represents the land of conventional “diets,” where
90 percent of the attention—and research funding, and energy, and anger,
and, of course, arguing—over nutritional biochemistry is focused. But it is
pretty simple, when you get down to it: identify one or more bogeymen in
your nutrition world, such as wheat gluten (for example), and exclude it. The
more ubiquitous the bogeyman, the more restrictive the “diet,” and the more
likely you are to reduce your overall caloric intake. Even if you decided to eat
nothing but potatoes, you would still lose weight, because a human being can
only choke down so many potatoes in a day. I’ve seen people do this, and it
works. The hard part is figuring out what foods to eliminate or restrict.
This wasn’t an issue for our ancestors. There is ample evidence to suggest
that they were opportunistic omnivores, out of necessity. They ate anything
and everything they could get their hands on: lots of plants, lots of starch,
animal protein whenever they could, honey and berries whenever possible.
They also seemed to be, at least on the basis of the study of the few
remaining hunter-gatherer societies, very metabolically healthy.
Should we do the same? Should we be opportunistic omnivores eating
anything and everything we can get our hands on? That’s how evolution has
formed us, but our modern food environment makes it a little too easy to find
food. Thus, being overnourished and metabolically unhealthy is now
commonplace. We have too many choices and too many delicious ways to
take calories into our body. Hence the need for dietary restriction. We need
to erect walls around what we can and cannot (or should not) eat.
The advantage of DR is that it is highly individualized; you can impose
varying degrees of restriction, depending on your needs. For example, you
could decide to eliminate all sugar-sweetened beverages, and that would be a
great first step (and a relatively easy one). You could go a step further and quit
drinking sweet fruit juices as well. You could quit eating other foods with
added sugar. Or you could go as far as reducing or eliminating carbohydrates
in general.
One reason carbohydrate restriction is so effective for many people is that
it tends to reduce appetite as well as food choices. But some people have a
harder time maintaining it than others. (Even I am pretty sure I could never
go back to a ketogenic diet for more than a few days.) While fat restriction
also limits food choices, it can be less effective at reducing appetite if you
pick the wrong low-fat foods to eat (e.g., high-carb junk food). If you
consume most of your carbohydrates in the form of Fruit Loops, for example,
you will still be very hungry all the time.
A major risk with DR is that you can still easily end up overnourished if
you are not deliberate about it. People tend to (erroneously) assume you can’t
eat too much if you’re just restricting fill-in-the-blank (e.g., carbohydrates).
This is incorrect. Even if done correctly and strictly, DR can still result in
overnutrition. If you cut out carbohydrates altogether but overdo it on the
Wagyu steaks and bacon, you will fairly easily find yourself in a state of
caloric excess. The key is to pick a strategy to which you can adhere but that
also helps achieve your goals. This takes patience, some willpower, and a
willingness to experiment.
We also want to be sure we’re not compromising our other goals along the
way. Any form of DR that restricts protein, for example, is probably a bad
idea for most people, because it likely also impairs the maintenance or growth
of muscle. Similarly, replacing carbohydrates with lots of saturated fats can
backfire if it sends your apoB concentration (and thus your cardiovascular
disease risk) sky-high.
A more significant issue with DR is that everyone’s metabolism is
different. Some people will lose tremendous amounts of weight and improve
their metabolic markers on a low-carbohydrate or ketogenic diet, while others
will actually gain weight and see their lipid markers go haywire—on the exact
same diet. Conversely, some people might lose weight on a low-fat diet, while
others will gain weight. I have seen this happen time and again in my own
practice, where similar diets yield very different outcomes, depending on the
individual.
For example, when my patient Eduardo came to see me a few years ago
with what turned out to be a case of full-blown type 2 diabetes, cutting his
carbohydrate intake was clearly the way to go. Type 2 diabetes is a condition
of impaired carbohydrate metabolism, after all. From the outside, Eduardo
seemed like a pretty healthy guy, with a soccer player’s build and a physical
job in construction. He certainly did not fit the (bogus) stereotype of the lazy,
gluttonous diabetic. But tests showed that he had almost no ability to store
excess sugar that he consumed. His hemoglobin A1c was 9.7 percent, well
into the diabetic red zone. Being Latino meant that Eduardo was at a higher
risk of NAFLD and diabetes to begin with, thanks to his genes. He wasn’t
even forty, but unless we did something drastic, he more than likely was
going to die a painful and early death.
The obvious first step was to wean Eduardo off carbohydrates almost
entirely. No more tortillas, rice, or starchy beans—and no Gatorade, either.
Because he worked outside in the heat, he was pounding about three or four
liters of “sports drinks” each day. I never once described this diet as
“ketogenic,” and Eduardo certainly wasn’t telling the guys on the job site
about his new trendy keto diet. He just wasn’t drinking Gatorade anymore. (I
also put him on the diabetes drug metformin, which is cheap as well as
effective.) Within about five months, Eduardo’s markers had all normalized,
and his diabetes seemed to have been reversed; his hemoglobin A1c was now
a completely normal 5.3 percent, just thanks to dietary changes and
metformin. And along the way he lost about twenty-five pounds. I’m not
saying this diet was the only possible path to this result, but this relatively
simple and achievable form of DR created enough of an energy imbalance
that he lost weight, and everything else improved in lockstep.
In the past, I was a huge proponent of ketogenic diets, finding them
particularly useful to manage or prevent diabetes in patients like Eduardo. I
also like that they have a strict definition, unlike “low carb” or “low fat.” A
ketogenic diet means restricting carbohydrates to such an extent that the body
begins metabolizing fat into “ketone bodies” that the muscles and brain can
utilize as fuel. A ketogenic diet helped fix Not-Thin Peter, and it had likely
saved Eduardo’s life. I thought it was the medicine that every metabolically
unhealthy person needed.
But my patients brought me back to earth, as they so often do. As a
physician, one often receives feedback in a very direct, personal way. If I give
someone a medication or a recommendation, I will find out pretty quickly
whether it is working. It’s not “data” in the strict sense, but it can be equally
powerful. I’ve had more than one patient for whom a ketogenic diet has
completely failed. They didn’t lose weight, and their liver enzymes and other
biomarkers failed to improve. Or they found it impossible to sustain. I’ve had
other patients who were able to stick to the diet, but then their lipid numbers
(especially their apoB) went through the roof, probably because of all the
saturated fats they were eating.
At the time, this confused me. What was wrong with them? Why couldn’t
they just follow the diet correctly? I had to remind myself of what Steve
Rosenberg used to say when a patient’s cancer progressed despite treatment:
The patient has not failed the treatment; the treatment has failed the patient.
These patients needed a different treatment.
The real art to dietary restriction, Nutrition 3.0–style, is not picking which
evil foods we’re eliminating. Rather, it’s finding the best mix of
macronutrients for our patient—coming up with an eating pattern that helps
them achieve their goals, in a way that they can sustain. This is a tricky
balancing act, and it requires us (once again) to forget about labels and
viewpoints and drill down into nutritional biochemistry. The way we do this is
by manipulating our four macronutrients: alcohol, carbohydrates, protein, and
fat. How well do you tolerate carbohydrates? How much protein do you
require? What sorts of fats suit you best? How many calories do you require
each day? What is the optimal combination for you?
Let’s now look at each of the four macronutrients in more detail.