Low carb (carbohydrate), high protein diets are the latest
dieting craze. However, before you jump on the band wagon,
you may want to consider a few things:
1. Low carb (ketogenic) diets deplete the healthy glycogen
(the storage form of glucose) stores in your muscles and
liver. When you deplete glycogen stores, you also dehydrate,
often causing the scale to drop significantly in the first week
or two of the diet. This is usually interpreted as fat loss when
it’s actually mostly from dehydration and muscle loss. By the
way, this is one of the reasons that low carb diets are so
popular at the moment – there is a quick initial, but deceptive
drop in scale weight.
Glycogenesis (formation of glycogen) occurs in the liver and
muscles when adequate quantities of carbohydrates are
consumed – very little of this happens on a low carb diet.
Glycogenolysis (breakdown of glycogen) occurs when
glycogen is broken down to form glucose for use as fuel.
2. Depletion of muscle glycogen causes you to fatigue easily,
and makes exercise and movement uncomfortable. Research
indicates that muscle fatigue increases in almost direct
proportion to the rate of depletion of muscle glycogen. Bottom
line is that you don’t feel energetic and you exercise and move
less (often without realizing it) which is not good for caloric
expenditure and basal metabolic rate (metabolism).
3. Depletion of muscle glycogen leads to muscle atrophy (loss
of muscle). This happens because muscle glycogen (broken
down to glucose) is the fuel of choice for the muscle during
movement. There is always a fuel mix, but without muscle
glycogen, the muscle fibers that contract, even at rest to
maintain muscle tone, contract less when glycogen is not
immediately available in the muscle. Depletion of muscle
glycogen also causes you to exercise and move less than
normal which leads to muscle loss and the inability to
maintain adequate muscle tone.
Also, in the absence of adequate carbohydrate for fuel,
the body initially uses protein (muscle) and fat. the initial
phase of muscle depletion is rapid, caused by the use of
easily accessed muscle protein for direct metabolism
or for conversion to glucose (gluconeogenesis) for fuel. Eating
excess protein does not prevent this because there is a caloric
When insulin levels are chronically too low as they may
be in very low carb diets, catabolism (breakdown) of
muscle protein increases, and protein synthesis stops.
4. Loss of muscle causes a decrease in your basal metabolic
rate (metabolism). Metabolism happens in the muscle. Less
muscle and muscle tone means a slower metabolism which
means fewer calories burned 24 hours-a-day.
5. Your muscles and skin lack tone and are saggy. Saggy
muscles don’t look good, cause saggy skin, and cause you to
lose a healthy, vibrant look (even if you’ve also lost fat).
6. Some proponents of low carb diets recommend avoiding
carbohydrates such as bread, pasta, potatoes, carrots, etc.
because of they are high on the glycemic index – causing
a sharp rise in insulin. Certain carbohydrates have always
been, and will always be the bad guys: candy, cookies, baked
goods with added sugar, sugared drinks, processed / refined
white breads, pastas, and rice, and any foods with added sugar.
These are not good for health or weight loss.
However, carbohydrates such as fruits, vegetables, legumes,
whole grain breads and pastas, and brown rice are good for
health and weight loss. Just like with proteins and fats, these
carbohydrates should be eaten in moderation. Large volumes
of any proteins, fats or carbohydrates are not conducive to
weight loss and health.
The effect of high glycemic foods is often exaggerated. It’s does
matter, but to a smaller degree than is often portrayed. Also,
the total glycemic effect of foods is influenced by the quantity
of that food that you eat at a sitting. Smaller meals have a lower
overall glycemic effect. Also, we usually eat several types of
food at the same time, thereby reducing the average glycemic
index of the meal, if higher glycemic foods are eaten.
Also, glycemic index values can be misleading because they
are based on a standard 50 grams of carbohydrate consumed.
It wouldn’t take much candy bar to get that, but it would take
four cups of carrots. Do you usually eat four cups of carrots
at a meal?
Regular exercisers and active people also are less effected by
higher glycemic foods because much of the carbohydrate
comsumed is immediately used to replenish glycogen stores in
the liver and muscle.
By the way, if you’re interested in lowering insulin levels,
there is a great way to do that – exercise and activity.
7. Much of the weight loss on a low carb, high protein diet, especially in the first few weeks, is actually because of
dehydration and muscle loss.
8. The percentage of people that re-gain the weight they’ve
lost with most methods of weight loss is high, but it’s even
higher with low carb, high protein diets. This is primarily due
to three factors:
A. You have lost muscle. With that comes a slower
metabolism which means fewer calories are burned 24
hours-a-day. A loss of muscle during the process of losing
weight is almost a guarantee for re-gaining the lost weight,
B. You re-gain the healthy fluid lost because of glycogen
C. It’s difficult to maintain that type of diet long-term.
D. You have not made a change to a long-term healthy
9. Eating too much fat is just not healthy. I know you’ve
heard of people whose blood levels of cholesterol and
triglycerides have decreased while on a low carb, high
protein diet. This often happens with weight loss, but it
doesn’t continue when you’re on a diet high in fat.
There are literally reams of research over decades that clearly
indicates that an increase in consumption of animal products
and/or saturated fat leads to increased incidence of heart
disease, strokes, gall stones, kidney stones, arthritic
symptoms, certain cancers, etc. For example, in comparing
countries with varying levels of meat consumption, there
is a direct relationship between the volume of meat consumption
in a country and the incidence of digestive cancers (stomach,
intestines, rectal, etc.).
Fat is certainly necessary, and desirable in your diet, but
they should be mostly healthy fats and in moderation.
Manufactured / synthetic “low fat” foods with lots of added
sugar are not the answer. Neither are manufactured / synthetic
“low carb” foods with artificial sweeteners or added fat. By
the way, use of artificial sweeteners has never been shown
to aid in weight loss and they may pose health problems.
According to Dr. Keith-Thomas Ayoob of Albert Einstein
College of Medicine in New York, “In my experience,
unless you’re willing to throw out decades of research,
you cannot ignore that diets chronically high in saturated
fats are linked to heart disease,” Dr. Ayoob is also a
spokesman for the American Dietetic Association
and says that low carb, high protein diets are an attempt
at a quick fix and not a long-term lifestyle change.
10. As someone recently told me, “it must work – people
are losing weight”. People that are truly losing fat on
low carb, high protein diets, are doing so because they
are eating fewer calories – that’s the bottom line. There
is no magic – the same can be done on a healthy diet.
11. Low carb diets are lacking in fiber. Every plant-based
food has some fiber. All animal products have no fiber. A
lack of fiber increases your risk for cancers of the digestive
track (because transit time is lengthened) and cardiovascular
disease (because of fibers effect on fat and cholesterol). It
also puts you at a higher risk for constipation and other bowel
12. Low carb diets lack sufficient quantities of the the many
nutrients / phytonutrients / antioxidants found in fruits,
vegetables, legumes, and whole grains, necessary for health
and aiding in prevention of cancer and heart disease. In fact,
you need these nutrients even more so when you’re consuming
too much fat as is often the case on a low carb high protein diet.
13. Amercans already consume more than twice the amount
of protein needed. Add to that a high protein diet and you
have far too much protein consumption. By the way, most people
don’t realize that all fruits, all vegetables, all whole grains,
and all legumes also contain protein. Animal products contain
larger quantities of protein, but that may not be a good thing.
Excess dietary protein puts you at a higher risk for many health
problems: gout (painful joints from high purine foods which are
usually high protein foods), kidney disease, kidney stones,
osteoporosis (excess dietary protein causes leeching of calcium
from the bones). By the way, countries with lower, healthier
intakes of protein also have a decreased incidence of
14. Low carb, high protein diets cause an unhealthy
physiological state called ketosis, a type of metabolic acidosis.
You may have heard the phrase, “fat burns in the flame of
carbohydrate”. Excess acetyl CoA cannot enter the Krebs
Cycle (you remember the old Krebs Cycle) due to insufficient
OAA. In other words, for fat to burn efficiently and without
production of excess toxic ketones, sufficient carbohydrate
must be available. Ketosis can lead to many health problems
and can be very serious at it’s extreme.
15. Bad breath. Often called “keto breath” or “acetone
breath”, it’s caused by production of acetones in a state of
So why the low carb, high protein craze? I believe there are
A. Weight loss (mostly muscle and muscle fluid) is often
rapid during the first few weeks. This causes people to think
they’re losing fat rapidly.
B. It gives you “permission” to eat the “bad foods”: bacon,
eggs, burgers, steak, cheese, etc., and lots of fat.
C. Many see it as the new “magic” they’ve been looking for,
although it’s been around, in various forms, since the
The good news is that there is a very healthy way to lose
weight, feel energetic, and to greatly increase your chances
of keeping it off. But that’s another article.
References: – Brooks, G, Fahey, T: Exercise Physiology – Human Bioenergetics
and its Applications. John Wiley and Sons, 1984.
– Cheatham, B, Kahn, CR: Insulin Action and Insulin Signaling
Network. Endocrine Review 16:117, 1995
– Fain, JN: Insulin Secretion and Action. Metabolism 33:672, 1984.
– Fitts, RH: Cellular Mechanisms of Muscle Fatigue. Physiological
Review 74:49, 1994
– Griffin, James, Ojeda, Sergio: Textbook of Endocrine
Physiology. Oxford University Press, 2000
– Guyton, A, Hall, J: Textbook of Medical Physiology. W.B.
Saunders Company, 2000.
– Herzog, W: Muscle Function in Movement and Sports. American
Journal of Sports Medicine 24:S14, 1996
– Hoffman, JF, Jamieson, JD: Handbook of Physiology: Cell
Physiology. Bethesda: American Physiological Society, 1997
– Kimball, SR, Vary, TC, Jefferson, LS: Regulation of Protein
Synthesis by Insulin. Annual Review Physiology 56:321, 1994.
– McArdle, William, Katch, Frank, Katch, Victor: Exercise
Physiology – Energy, Nutrition, and Human Performance.
Lea and Febiger, 1981.
– Mcdougall, MD, John: The Mcdougall Plan. New Century
– Simopoulos, AP, Pavlou, KN: Nutrition and Fitness. Basel:
copyright 2007 by Greg Landry, M.S.