Nutrition Performance - Nutritional & Metabolic Aspects of Carbohydrate Restriction
An Interview with Dr. Richard Feinman
''What right has the federal government to propose that the American people conduct a
vast nutritional experiment [high-carbohydrate/low-fat diet], with themselves as subjects, on the
strength of so very little evidence that it will do them any good?'' —A question posed to
Congress by Dr. Phil Handler back in 1980 when he was president of the National Academy of
Sciences
For decades, well-meaning health authorities have proudly taught us that a diet low in
fat and high in starch promotes fat loss and decreases the risk of chronic diseases. It should be
noted, however, that there’s little, if any, scientific evidence supporting this notion. In fact, the
current epidemic of diabetes and obesity has been, over the past three decades, accompanied
by a significant decrease in fat consumption and an increase in carb consumption. Thus,
alternative dietary approaches are clearly needed.
Strength-power athletes already know what science is now showing. Replacing carbs
(especially processed carbs) with protein and fat is an effective way to promote fat loss while
sparing muscle mass, so it would be wise not to follow the dietary guidelines of the American
Heart Association or the American Dietetic Association. Also, purported adverse effects of highprotein/
low-carb diets are false or at least greatly exaggerated.
MD tracked down a leading low-carb researcher, Richard Feinman, PhD, to provide us
with answers to our questions regarding carb restriction. Dr. Feinman is a professor of
biochemistry at the State University of New York Downstate Medical Center with a long career
in protein chemistry. His current interest in nutrition and metabolism derives from his many
years of teaching these subjects in the College of Medicine at SUNY. Dr. Feinman is also coeditor-
in-chief of Nutrition & Metabolism, a leading scientific journal in the area of nutritional
biochemistry, and an organizer of the Nutrition & Metabolism Society Conference on Nutritional
and Metabolic Aspects of Carbohydrate Restriction.
AM
nutrition?
RF
the school of medicine at the State University of New York (SUNY) Downstate Medical Center. I
think, however, if there’s a single event that prompted me to get involved, it’s a seminar I heard
in which the speaker was saying that low-carbohydrate diets are no more effective, calorie-forcalorie,
than other diets and the speaker quoted the laws of thermodynamics. Now, this was
different from what I teach and it also happened that I was doing work in physical chemistry at
the time and I knew that the laws of thermodynamics said no such thing. So my colleague Dr.
Eugene Fine and I set out to explain why the so-called "calorie-is-a-calorie" idea is wrong.
AM
of thermodynamics. Aren’t you limited by the calories you take in?
RF
than that. Conservation of energy, that is, the first law of thermodynamics, is only a
bookkeeping law. It does not predict how caloric intake is distributed between weight gain,
activity, heat generated and— this may be very important— growth and tissue changes. To
know what happens you need the second law, which says, in essence, all processes are
somewhat inefficient and particular chemical changes may be very wasteful of energy. We
explained that the make-up of a diet, how much carbohydrate, how much protein predicted very
different efficiencies for the diets of different composition. We pointed out that the energy
necessary for the processing of protein, the cycling of intermediates (running the engine on idle,
so to speak) and involvement of uncoupling proteins were the kind of mechanisms that could
account for inefficiency in carbohydrate restriction. The important point is that many
experiments have already been done showing that low-carbohydrate diets are, in fact, more
efficient for weight loss, that is, more inefficient in storing fat. So, you can always argue about
how accurate the measurements are, but many of these studies were very carefully done and,
since we now showed that there’s nothing theoretically wrong with them, we have to accept that
they are possible.
AM
diet?
RF
really difficult, so any advantage you can get will help. The additional benefit from the metabolic
effect can be pretty large for some people. Also, critics of low-carbohydrate diets say that it’s
just calorie reduction, but they are forgetting that it is not "just"; it is very hard to get people to
cut calories and traditional methods that urge willpower to target calorie reduction have no great
success— otherwise, we wouldn’t have an obesity epidemic. In fact, you would think that a diet
that’s quite flexible— you only have to cut down on carbs, it’s up to you what, if anything you
replace it with— you would think that a diet that spontaneously reduced caloric intake would be
widely embraced by nutritionists.
AM
many practicing physicians and nutritionists are opposed to carbohydrate restriction? And, I
guess, what our readers really want to know is, how should they deal with this negative reaction
if they want to try a low-carbohydrate approach?
RF
is going to give you a consensus approach, which is always conservative, and many of their
experts have pretty much made up their minds and aren’t interested in any second opinions. On
the other hand, although people are slow to change their minds, things are changing and many
practitioners are more open-minded than the health agencies and the "experts" you hear on
television. We took a survey of an online support group, the Active Low-carber’s Forum, which
incidentally, has more than 82,000 members (www.forum.lowcarber.org). The great majority of
their members follow some kind of low-carb diet, most of them quite successfully. We got about
3,000 responses to our survey: about half of the respondents had consulted a physician or other
health professional before or during their diet. Fifty-five percent said that the physician was
supportive and 28 percent said that the physician had no opinion, but was supportive after they
brought in good results. So, I think it’s generally a good idea to consult a physician if you’re
going to undertake weight loss, especially in connection with exercise, which is an important
component, but you should not assume that they will be negative about carb restriction. If they
are, it’s appropriate for you to ask for reasons and to expect that they satisfy you that any
objections they have to a diet makes sense (some medical conditions probably preclude lowcarbohydrate
strategies).
AM
might fit into a low-carbohydrate diet. We certainly hear of the dangers of such diets for
exercise.
RF
special requirements and people who want to stay fit and engage in athletic activities at a nonprofessional
or semi-professional level. For the latter group, which is most of us, if they’re in
good health, there’s no identified danger of low-carbohydrate dieting. Indeed, most people
report feeling better, having more energy and are more comfortable being active. The dire
predictions of damage to healthy kidneys have never been found (although, in any case, there’s
a benefit to low carbohydrates without substituting much protein). The continued warnings about
cardiovascular disease are, if anything, backward because most lipid markers improve and
epidemiologic studies from Harvard show that replacing unsaturated fat in the diet with
carbohydrate is worse than replacing unsaturated fat with saturated fat (again, there’s a benefit
to low carbohydrates without substituting much fat).
There are all levels of carbohydrate reduction and if your primary motivation is weight
loss/fat loss, you may choose a very low-carbohydrate diet along the lines of the first two weeks
of popular diets such as the Atkins diet, South Beach diet or Protein Power. Here, you’re on a
serious diet and some adjustment may be required— this is true of very low calorie diets as
well. Usually a period of acclimation is required. Common sense is in order. If you feel weak or
dizzy, back off on your diet, whatever it is. If you have just started and feel light-headed, don’t
get into a basketball game. This isn’t expert opinion, just common sense for any diet. If you’re
not feeling better in a few days, it’s not a good diet for you, again, whether it’s low-carb, highcarb,
or whatever.
AM
carbs are reduced?
RF
you’re overweight and think you’re not performing (perception is part of the mix), you may have
to make a decision on priorities. As I mentioned before, an adjustment period may be
necessary. Steve Phinney showed that with an adjustment period, even elite athletes can reach
high performance. It should be said, however, that we don’t know all the answers or all the
possible variations. Fine tuning performance can involve the timing of nutrient intake. An area of
investigation for competition athletes is whether the benefits of chronic, day-to-day low carb can
be incorporated into a program utilizing the benefits of carb-loading before an event.
This gets to your question about glycogen, which is certainly reduced on a lowcarbohydrate,
typically at the 60 percent level, but it’s protected in the sense that the glucose
your body produces replenishes glycogen. I assume most of your readers know that on a
carbohydrate-restricted diet, your body’s requirement for glucose is supplied by the process
known as gluconeogenesis where glucose is synthesized from protein [amino acids] or other
metabolites. Gluconeogenesis works hand-in-hand with glycogen synthesis on a low-carb diet
to maintain a working level. It’s important, however to ask what the role of glycogen is. Here,
again, there’s a difference with competition athletes for whom the bottom line on glycogen may
be the more the better. For most people doing moderate exercise, however, excess glycogen
may not be necessary or even desirable since it’s tied into other aspects of metabolism such as
blood glucose levels. So, the bottom line is that, whereas there are always individual
differences, performance isn’t inherently impaired and glycogen stores are within the functional
range, but peak performance may require experimentation.
The most important point for most people is that if you’re trying to lose body fat, data
from Donald Layman’s lab among others, has shown that there’s not only a benefit to low
carbohydrates, but the combination of this kind of diet with exercise is especially effective. Also,
work from Jeff Volek’s lab and your own commentary in Nutrition & Metabolism pointed out the
general benefit in increasing lean mass at the expense of fat or carbohydrate restriction,
although this is not universally acknowledged.
Editor’s Note: It should be noted that full adaptation of macronutrient metabolism
requires a number of weeks, so short-term studies examining the effects of high-carb versus
low-carb on exercise performance are scientifically worthless. A free, full-text paper of my
recent commentary entitled "Very-low-carbohydrate diets and preservation of muscle mass" is
available at www.nutritionandmetabolism.com.
AM
RF
high carbohydrates, there’s going to be a period of adaptation if they’re going to switch to
carbohydrate restriction. The literature shows that some clearly do better on high carbs, some
do the same on high carbs and low carbs, but don’t like low carbs, and some do fine on low
carbs and, as I mentioned, people are investigating whether both approaches can be combined.
Also, it’s almost by definition that the peak athlete is outside the norm, making it difficult to
present a clear generalization. I myself am hoping for a late blossoming of exceptional athletic
ability and should that happen I’ll get back to MD on that.
AM
on carbohydrate restriction that was held in Brooklyn in January. I see that the conference
covered a wide range of subjects, but if you had to pick a single highlight of the meeting what
would it be?
RF
now have the sense that type 2 diabetes (where patients are capable of making insulin, but
have reduced responses, a so-called insulin resistance) may be continuous with and even be
caused by less drastic conditions that include obesity and susceptibility to cardiovascular
disease, which we all have to deal with. So, the demonstration by Mary Vernon and Will Yancy
that many type 2 diabetics who went on low-carbohydrate diets reduced or eliminated
medication I consider a demonstration of the impressive metabolic modifications that are
possible. If this can be achieved in what can be a severe disease, it may hold potential for
subclinical metabolic problems.
AM
RF
people are beginning to appreciate the value of carbohydrate restriction. The problem is the
continuing emphasis on low fat, which hasn’t been a productive piece of advice as indicated by
the very dismal performance in the recently published Women’s Health Initiative. Of course, if
high carbs are preferred for taste or whatever reason, then it’s probably good to keep fat lower.
Also, for weight loss everybody agrees that reducing calories by removing fat would be a good
thing, but the key point is that replacement of fat with carbohydrate is generally deleterious to
cardiovascular health and obesity. This is well established in the literature.
In the end, an appreciation of the importance of carbohydrate restriction is inevitable
since the science so clearly points in that direction. At that point, I would hope recognition will
be given to the people who’ve been struggling against orthodoxy to produce the data— Steve
Phinney, Jeff Volek, Eric Westman and Mary Vernon among others. I would also hope that we
could understand as well the contribution of Dr. Robert C. Atkins. Whereas his diet is a popular
diet and in the final implementation will undergo many changes, his contribution, especially in
the face of very intemperate criticism should be appreciated. It’s a historical fact that he
proposed an idea that came precisely at the time low fat was being proposed as a goal.
Hopefully, the hostile response of the scientific community to Dr. Atkins will be understood in
this historical context and it will be realized that it wasn’t our finest hour.
Bottom Line
It’s becoming increasingly clear that the conventional high-carb/low-fat diet is far form
the ideal diet. High-carbohydrate meals raise blood glucose and insulin secretion, thereby
increasing the risk of obesity, diabetes and heart disease. The preponderance of evidence
strongly suggests that the substitution of carbohydrate for protein and fat will lead to more
favorable changes in body composition. Also, a higher-protein/lower-carbohydrate diet
increases satiety and stabilizes blood insulin. However, one diet approach doesn’t fit all.
Identifying specific needs, goals and the activity level of each individual is the key for success.
: Well, it’s already beginning to make inroads into traditional thinking and most: Where do you see the field of carbohydrate restriction going in the future?: Well, oddly I would focus on a couple of the clinical papers on diabetes because we: Returning to reality, Dr. Feinman, you were the chief organizer of the conference: This is outside my area of expertise, but my understanding is that for athletes on: Well, what about competition athletes?: On performance, there is little evidence of a decrement for most people, but if: There’s also the question of performance. Don’t glycogen stores go down when: Well, first we have to distinguish between competition athletes who may have very: Our readers, of course, are very interested in the question of exercise and how it: Well, first of all, big agencies have many opinions and rely on committees and this: That brings me to the question: why do you think official organizations and so: That’s also true and may be the major effect for most people, but weight loss is: But isn’t there a spontaneous reduction in intake of calories on a low-carbohydrate: Of course to a large extent you are limited by caloric intake, but there’s more to it: What’s the explanation? Most of us think of conservation of energy when we think: Well, as you mentioned in your introduction, I’ve taught nutrition and metabolism in: I understand you’re trained as an enzyme chemist. How did you get involved in
