Subject: Another Point of View -Taken from the Archives

[Guest guest]

" H & M Feld " <ari-@e...>;

Fri Nov 28, 2003 5:41 pm

Another Point of View

 

 

Volume 88 . Number 1 . July 1, 2001

2001 The American College of Cardiology

 

Metabolic effects of high-protein, low-carbohydrate diets

Margo A. Denke, MD a

---

 

a Division of Endocrinology and Center for Human Nutrition

University of Texas Southwestern Medical Center at Dallas

Dallas, Texas, USA

---

 

Address for reprints: Margo A. Denke, MD,

Center for Human Nutrition,

The University of Texas

Southwestern Medical Center at Dallas,

5323 Harry Hines Boulevard,

Dallas, Texas 75390-9052

E-mail address: mde-@m...

 

Manuscript received January 16, 2000;

revised manuscript received January 6, 2001,

accepted January 6, 2001

PII S0002-9149(01)01586-7

 

Weight-losing diets appeal to the growing population of overweight

Americans.

Fad diets promise rapid weight loss, easy weight loss, limited

restrictions onportion sizes of favorite foods, and above all an

enhanced sense of well being.

 

The popularity of fad diets points out the honest promises of

traditional weight loss diets.

Traditional weight loss diets promise slow weight loss

of 0.45 to 0.9 kg/week.

 

The weight loss is nothing but easy, because portion sizes of

nearly all foods except low-calorie " free foods " must be

continuously evaluated and tracked.

 

Claiming an enhanced sense of well being is hardly

appropriate for a traditional diet-most patients report

dissatisfaction from the constant vigilance over dietary intake.

 

Through discipline and perseverance,traditional weight loss programs

try to teach a patient a new lifestyle of healthy eating.

Unfortunately, 70% of successful weight losers return to their old

habits and within 2 years regain at least half of the weight lost.

 

These patients typically have little insight into the reasons why

the weight was regained,and consider themselves " failures " to

traditional diet programs. They become prime targets for diets

promising rapid and easy weight loss.

 

 

Prototypes of the high-protein, low-carbohydrate diets

High-protein, low-carbohydrate diets have a long history of cyclic

popularity.Greek Olympians ate high meat, low vegetable diets >2,000

years ago to improve athletic performance.

 

Dr. William Harvey recommended a diet prohibiting sweet

and starchy foods and permitting ad lib consumption of meats for

patients who needed diuresis.

 

As the basic understanding of nutrition and essential vitamins

developed, these diets fell out of favor. They regained popularity

in the late 1960s and early 1970s with the publication of the

Atkins' Diet, Stillman's Diet, The Drinking Man's Diet, the

Scarsdale Diet, and the Air Force Diet.

 

The American Medical Association strongly criticized these diets,[1]

leading to their submergence on the popular diet trend.

Resurgence of low carbohydrate diets has been fueled by rising

obesity and insulin resistance in the general population. Although

the Atkins' Diet is the prototype of the low carbohydrate diet, The

Sugar Busters Diet,Carbohydrate Addicts Diet, Protein Power Diet,

and the Zone Diet are all variations on this common theme.

 

Several diets promise that, as long as you restrict carbohydrates,

you will lose weight and you can eat as much food as you want.

There may be a kernel of truth to this claim. For some patients,

high-protein intake suppresses appetite.

For other patients, ketosis from carbohydrate restriction suppresses

appetite.

Restricting carbohydrate eliminates some popular foods that are

often consumed in excess such as bread, cereal, soft drinks, french

fries, and pizza. By simply excluding carbohydrate foods, patients

following the Atkins diet typically consume 500 fewer calories a

day.

How low-carbohydrate diets produce initially greater weight loss

Reducing caloric intake by 500 kcal/day should result in a 0.45- to

0.9-kg weight loss each week.

 

However, low-carbohydrate, high-protein diets typically produce a 2-

to 3-kg weight loss in the first week. This added weight loss is

not due to the miracle of " switching the body's metabolism over to

burning fat stores. "

 

It is due to a diet-induced diuresis.

 

When carbohydrate intake is restricted, 2 metabolic processes occur,

both of which simultaneously reduce total body water content.

 

The first process is mobilization of glycogen stores in liver and

muscle. Each gram of glycogen is mobilized with approximately 2 g

of water. The liver stores approximately 100 g of glycogen and

muscle has 400 g of glycogen.

 

Mobilization glycogen stores result in a weight loss of

approximately 1 kg. Patients notice this change as a reduction in

symptoms of " bloating " and are very pleased with the effect.

 

The second process is generation of ketone bodies from catabolism of

dietary and endogenous fat.

 

Ketone bodies are filtered by the kidney as nonreabsorbable anions.

Their presence in renal lumenal fluids increase distal sodium

delivery to the lumen,

and therefore increase renal sodium and water loss.

 

In a study comparing an 800-calorie mixed diet with an 800-calorie

low-carbohydrate, high fat diet,[5] 10-day weight loss was 4.6 kg on

the ketogenic diet and 2.8 kg on the mixed diet.

 

Energy-nitrogen balanced studies documented that the difference in

weight lost was all accounted for

by losses in total body water.

 

Long-term weight loss is influenced by caloric restriction, not

carbohydrate restriction

The diuretic effect of low-carbohydrate intake is limited to the

first week of the diet.

 

The remaining weight loss is a function of the laws of energy

balance.Calories from any source determine the success of additional

weightloss.

 

In the only published study of Atkins diet, patients following the

diet reduced caloric intake by 500 kcal/day. The average weight loss

was 7.7 kg at 8 weeks, which is no greater than that expected from

caloric restriction alone.[6]

 

The bility of low carbohydrate intake to generate ketones has been

touted as a relative avantage for losing weight. However, this

advantage was not confirmed in a 1-month study comparing ketogenic

with nonketogenic hypocaloric diets.[7]

 

Most comparison studies have evaluated the relative advantages of

either a low carbohydrate or low fat hypocaloric diets; some studies

found a slight 1- to 3-kg greater weight loss on a low-carbohydrate

diet,[8] [9] [10]

[11] others a slight advantage with a high-carbohydrate diet,[12]

but most studies have observed no statistical advantage of a

low-carbohydrate diet.[13]

 

[14] [15] [16][17] [18] The preponderance of evidence suggests that

as long as caloric intake remains constant,[19] there is no

intrinsic advantage to cutting carbohydrate intake.[20]

 

Untoward metabolic effects

Complications from ketosis

 

Eucaloric ketogenic diets have been prescribed as part of an

antiepileptic regimen in children with refractory seizure disorders.

Children following these ketogenic diets have higher rates of

dehydration, constipation, and

kidney stones. Other reported adverse effects include

hyperlipidemia, impaired neutrophil function, optic neuropathy,

osteoporosis, and protein *deficiency*.[21]

 

 

Because ketogenic diets effect the central " nervous system " , it has

been suspected that ketogenic diets may alter cognitive function.

 

In a randomized weight loss study comparing a ketogenic with a

nonketogenic hypocaloric diet,

subjects consuming the ketogenic diet had impairments in higher

order " mental processing " and flexibility than those following the

nonketogenic

diet.[7]

 

Complications from high saturated fat intake

 

Despite the beneficial effects of weight loss, diets that promote

liberal intake of high fat meats and dairy products raise

cholesterol levels.

 

In a study 24 subjects following the Atkins'-type 4-week induction

diet, then 4 weeks maintenance diet,[6] low-density lipoprotein

cholesterol levels increased significantly from 127 to 151 mg/dl.

 

Similar increases in total cholesterol (13%) were reported in a

study of patients following the Stillman diet.[22]

 

 

Complications from high fat intake

 

High fat diets increase free fatty acid flux and circulating free

fatty acids.

Fasting plasma free fatty acids may have a pro-arrhythmic effect in

cardiac muscle.

 

A number of mechanisms have been suggested including apossible

detergent effect of circulating free fatty acids on cell membranes

and

direct effects of acylcarnitine on cellular ion channels and

exchangers.

 

 

Complications from exclusion of fruits, vegetables, and grains

Because they exclude fruits, vegetables, and grains, low-

carbohydrate,high-protein diets are deficient in micronutrients.

 

Children consuming low-carbohydrate ketogenic diets have reduced

intakes

of calcium,magnesium, and iron.[21] Two sailors following a

low-carbohydrate, high-protein hypocaloric diet during an extended

voyage developed optic neuropathy from thiamine deficiency.[23]

 

Although vitamin deficiencies can be circumvented by

supplemental multivitamins, even supplemented low-carbohydrate diets

will still be deficient in a growing number of important,

biologically

active phytochemicals present in fruits, vegetables, and grains.

 

 

Complications from high-protein intake

 

Increasing the protein content of a diet significantly increases

glomerular filtration rate.[24] [25] Increases in glomerular

filtration

rate are likely explained by increased renal capillary permeability.

 

Unfortunately, this compensatory response to the greater production

of nitrogen is

insufficient to clear protein by-products, and blood urea nitrogen

levels increase.

 

High protein diets significantly lower urinary pH by increasing

titratable acid concentrations.[25] [26] High protein intakes

provide a

greater **uric acid** load to the kidney.

 

Despite increases in urinary uric acid excretion,

increases in serum uric acid are observed.[6] [26]

 

Untoward long-term effects

Development of nephrolithiasis

 

Hypercalciuria is a risk factor for nephrolithiasis. High-protein

diets induce hypercalciuria by several different mechanisms.

High-protein diets increase glomerular filtration rate and decrease

renal tubular reabsorption of calcium.

 

The relation between dietary protein intake and calcium excretion

(Table 1) is clearly linear.[27]

 

 

TABLE 1. Graded Effects of High-Protein Diets on Urinary Calcium

Excretion

* Percent calories calculated assuming 70-kg average subject weight,

2,400-calorie diet.

? Significantly different from low-protein diet.

Diet Duration

% Calories from Protein*

No. Creatinine Clearance (ml/min)

Urinary Calcium Excretion (mg/24 h)

 

Low Medium High Low Medium High

15 d 1%/12%/25% 6 98 105 122 51 99 161

4 d 8%/12%/25% 16 85 95 107 108 129? 196?

15 d 8%/16%/24% 33 168 240? 301?

15 d 8%/16%/24% 9 217 303? 426?

15 d 8%/16%/24% 9 168 240? 301?

 

 

The stone-forming propensity of the hypercalciuria induced by high-

protein diets is aggravated by other changes in urine composition.

 

A high animal protein diet reduces gastrointestinal alkali

absorption,

leading to reduced urinary citrate.[28]

 

Hyperuricemia and hyperuricosuria are also associated

with excess intake of animal protein. Animal protein is a rich

source of

sulfur-containing amino acids; amino acids have a greater propensity

to lower urinary pH.

 

Adding a carbohydrate restriction to a high-protein diet exacerbates

many of these parameters. Low-carbohydrate intake further reduces

urinary pH by inducing ketosis.

 

Limiting the intake of vegetables and fruits further

reduces urinary citrate by reducing dietary sources of alkali.

 

Thus, high-protein,low-carbohydrate diets are associated with

hypercalciuria,hyperuricosuria, and hypocitraturia, which can all

contribute to renal calculi formation.

 

 

Development of osteoporosis

 

High-protein, low-carbohydrate diets generate a high acid load,

resulting in a subclinical chronic metabolic acidosis.

Metabolic acidosis promotes calcium mobilization from bone.[29]

 

Osteoclasts and osteoblasts respond to small changes

in pH in cell culture; thus, a small decrease in pH results in a

large burst of bone resorption.

 

The effects of varying dietary protein intakes on bone turnover has

been carefully documented in young women consuming metabolic diets.

 

High-protein diets increase renal calcium excretion, raised

parathyroid

hormone levels, and raise urinary N-telopeptide concentrations.

 

Markers of bone formation (alkaline phosphatase and osteocalcin)

remain steady, suggesting that high-protein diets increase bone

resorption without affecting the rate of bone formation.[27]

These effects may be exaggerated in older persons who tend to have

decrements in renal clearance of acid and higher serum parathyroid

hormone concentrations.[29]

 

 

Progression of chronic renal insufficiency

 

In several small, randomized, controlled dietary trials, dietary

protein restriction retarded the progression of diabetic nephropathy

to

end-stage renal (kidney) disease.[30]

 

High-protein, low-carbohydrate diets have a weak effect

at reducing creatinine clearance over time, and could potentially

hasten

renal failure in patients with baseline renal insufficiency.

 

Patients are inherently attracted to the simple, permissive dietary

instructions: eat as much as you want of foods containing fat and

protein, but don't eat foods containing carbohydrate. As promised,

almost everyone loses weight during the first week.

 

Low-carbohydrate diets cause a greater initial

weight loss from a physiologic diuresis accompanying the obligate

loss of glycogen stores and renal clearance of ketone bodies.

 

Once glycogen stores have been liberated, and a new steady state for

total body sodium has been achieved,

these diets hold no greater promise for weight loss than any other

caloric restricted diet.

 

High-fat, low-carbohydrate diets can be harmful.

 

The diet plan is deficient in micronutrients. Consuming ad libitum

fatty meats raises total and low-density lipoprotein cholesterol

levels.

High-protein, low-carbohydrate intakes create a subclinical

metabolic

acidosis, and increase blood urea nitrogen and uric acid levels.

 

Resultant urine acidification,hyperuricosuria,and hypercalciuria

increase urine lithogenicity.

 

Trying to convince a devotee to stop the diet uncovers yet another

deleterious effect; ketogenic

diets impair higher order cognitive function.

 

High-protein, low-carbohydrate diets have untoward clinical

consequences for patients with coronary artery disease,

 

including progression of diabetic nephropathy, exacerbation of gouty

diathesis,

increases in circulating free fatty acids, and increases in low-

density lipoprotein cholesterol levels.

 

High-protein, lowcarbohydrate diets are not superior weight-losing

diets and should not be recommended.

 

References

 

1. Anonymous. A critique of low-carbohydrate ketogenic weight

reduction regimens. A review of Dr. Atkins' diet revolution. JAMA

1973;224:1415-1419.

2. Johnstone AM. Effect of overfeeding macronutrients on day-to-day

food intake in man. Eur J Clin Nutr 1996;50:418-30. Abstract

3. Yudkin J. The treatment of obesity by the high fat diet. Lancet

1960;2:939-41.

4. Kolanowski J. On the mechanisms of fasting natriuresis and of

carbohydrate-induced sodium retention. Diabetes Metab 1977;3:131-43.

5. Yang MU, Van Itallie TB. Composition of weight lost during short-

term weight reduction. Metabolic responses of obese subjects to

starvation and low-calorie ketogenic and nonketogenic diets. J Clin

Invest 1976;58:722-30.

 

Abstract

6. LaRosa JC, Fry AG, Muesing R, Rosing DR. Effects of high-protein,

low-carbohydrate dieting on plasma lipoproteins and body weight. J

Am Diet Assoc 1980;77:264-70. Abstract

7. Wing RR, Vazquez J, Ryan C. Cognitive effects of ketogenic weight

reducing

diets. Int J Obes Relat Metab Disord 1995;19:811-6. Abstract

8. Lewis SB, Wallin JD, Kane JP, Gerich JE. Effect of diet

composition on metabolic adaptations to hypocaloric

nutritioncomparison of high

carbohydrate and high fat isocaloric diets. Am J Clin Nutr

1977;30:160-70.

 

Abstract

9. Rabast U, Kasper H, Schonborn J. Obesity and low-carbohydrate

diets-comparative studies. Nutr Metab 1977;21(suppl 1):56-9.

Citation

10. Alford BB, Blankenship AC, Hagen RD. The effects of variations

in carbohydrate, protein, and fat content of the diet upon weight

loss,

blood values and nutrient intake in adult obese women. J Am Diet

Assoc 1990;90:534-40.

 

Abstract

11. Baron JA, Schori A, Crow B, Carter R, Mann JI. A randomized

controlled trial

of low carbohydrate and low fat/high fiber diets for weight loss. Am

J Publ Health 1986;76:1293-6.

12. Rabast U, Vornberger KH, Ehl M. Loss of weight, sodium and water

in obese persons consuming a high- or low-carbohydrate diet. Ann

Nutr Metab 1981;25:341-9.

Abstract

13. Davie M, Abraham RR, Godsland I, Moore P, Wynn V. Effect of high

and low-carbohydrate diets on nitrogen balance during calorie

restriction in obese subjects. Int J Obes 1982;6:457-62. Citation

14. Piatti PM, Pontiroli AE. Insulin sensitivity and lipid levels in

obese subjects after slimming diets with different complex and

simple carbohydrate content. Int J Obes 1993;17:375-81.

 

15. Rumpler WV, Seale JL. Energy intake restriction and diet

composition effects

on energy expenditure in men. Am J Clin Nutr 1995;53:430-6.

16. Low CC, Grossman EB, Gumbiner B. Potentiation of effects of

weight loss by monounsaturated fatty acids in obese NIDDM patients.

Diabetes 1996;45:569-75.

 

Abstract

17. Golay A, Allaz AF, Morel Y, de Tonnac N, Tankova S, Reaven G.

Similar weight loss with low- or high-carbohydrate diets. Am J Clin

Nutr 1996;63:174-8.

 

Abstract

18. Golay A, Eigenheer C, Morel Y, Kujawski P, Lehmann T, de Tonnac

N. Weight-loss with low or high carbohydrate diet? Int J Obes Rel

Metab Disord 1996;20:1067-72.

19. Skor AR, Toubro S, Ronn B, Holm L, Astrup A. Randomized trial on

protein vs. carbohydrate in ad libitum fat reduced diet for the

treatment of obesity. Int J Obes 1999;23:528-36.

20. Shah M, Garg A. High fat and high carbohydrate diets and energy

balance. Diabetes Care 1996;19:1142-52.

Abstract

21. Tallian K, Nahata M, Tsao CT. Role of ketogenic diet in children

with intractable seizures. Ann Pharmacother 1998;32:349-61. Abstract

22. Rickman F, Mitchell N. Changes in serum cholesterol during the

Stillman diet. JAMA 1974;228:54-8. Citation

23. Hoyt III CS, Billson FA. Low-carbohydrate diet optic neuropathy.

Med J Aust 1977;1:65-6.

Abstract

24. Kerstetter JE, O'Brien KO, Insogna KL. Dietary protein affects

intestinal

calcium absorption. Am J Clin Nutr 1998;68:859-65. Abstract

25. Schuette SA. Studies of the mechanism of protein induced

hypercalciuria in older men and women. J Nutr 1980;110:305-15.

 

Abstract

26. Fellstrom B, Danielson BG, Karlstrom B, Lithell H, Ljunghall S,

Vessby B.

The influence of a high dietary intake of purine-rich animal protein

on urinary urate excretion and supersaturation in renal stone

disease. Clin Sci 1983;64:399-405. Abstract

 

27. Kerstetter JE, Mitnick ME, Gundberg CM, Caseria DM, Ellison AF,

Carpenter TO, Insogna KL. Changes in bone turnover in young women

consuming different levels of dietary protein. J Clin Endocrinol

Metab 1999;84:1052-5.

 

Full Text

28. Breslau NA, Brinkley L, Hill KD, Pak CY. Relationship of animal

protein-rich diet to kidney stone formation and calcium metabolism.

J Clin Endocrinol Metab

 

1988;66:140-6. Abstract

29. Barzel US, Massey LK. Excess dietary protein can adversely

affect bone. J Nutr 1998;128:1051-3. Abstract

30. Kasiske BL, lakatua JD, Ma JZ, Louis TA. A meta-analysis of the

effects of dietary protein restriction on the rate of decline in

renal function. Am J Kidney Dis 1998;31:954-61. Abstract

_________________

 

JoAnn Guest

mrsjoguest

DietaryTipsForHBP

http://www.geocities.com/mrsjoguest

[Guest guest]

---Hi Joy,

The aticle to which you are referring was written by doctors who

were well aware of Dr. Atkins and his work. Although I'm not sure

that they are specifically talking about Dr. Atkins, but of high

protein and low carb diets in general.

 

I certainly am aware of his books. My daughter followed his

regimen religiously and read his books as well.

I became very concerned about her in the meantime because she was

eating all of his muffin, bread mixes and chocolate bars loaded with

those devastating hydrogenated sugar alcohols (I sent on an article

about that too!).She eventually became very sick and had to

discontinue the diet. Actually she discontinued it after she came

down with the flu. Her immune system became so depraved that she was

no longer her usually cheerful self, very sickly and with

innumerable digestive and health problems as well

 

My main concern with low carb diets is regarding the sugar

alchols and the resulting muscle `loss', not to mention irreversible

kidney malfunction

 

When the body ( in the absence of carbohydrates) keeps on burning

protein for `fuel',the protein is taken away from other important

bodily organs and the muscles, especially the muscles of the heart,

etc.

Notice that one of the primary causes of concern centers on the

burning of protein for the body's fuel. When there is a lack of

carbs in the diet, the body `burns' protein instead, which amounts

to a basic ultimate protein `deficiency'…if that makes any sense.

This is one of the conditions the physician listed in his article.

Think about it! The protein is burned for fuel because of the

ultimate lack of carbs. Sooooo….where does the body derive the

protein it needs for its muscles and other organs? There is none,

its all burned out.

This is just one of the ways this diet proves to be harmful to our

bodies. Muscle LOSS…inevitably never to be replaced. This can be

very serious! It IS serious!

 

I would challenge you to take a few moments and really read the

article, rather than just skimming over it. Read it in depth, just

like you read the Atkins books. You will see that it all makes

sense. There IS a real danger here. These are well meaning people

who have our best interests at heart.

 

I would be the first to admit that atkins has many good points in

his diet. he advises us to eat the good fats… i.e. olive oil, etc.

He also advises that we should not eat sugar, white breadas and

other simple carbs. All this is very good. If one were on the

standard american diet, this would be a step up for them.

He advises that we should include fish in our diets…another very

good point in his books. He advocates drinking goat milk.

He does include many of the more healthy vegetables in his diet.

However considering the overall concept, as the experts say, it

would not be conducive to a long healthy life.

It puts an extra load on the kidneys, elevates acidity which

deprives our skeleton of much needed calcium and is not at all

conducive to good cardiovascular health!

 

I would not recommend this diet to anyone whom I really cared

about. I would be very worried about their health and well being the

entire time they were doing it.

I drew a deep breath of relief when I found that my daughter had

given up trying Atkins. In my opinion, the damage done is just not

worth the few pounds lost!

 

I am just conveying the fat facts as I see them. Please do not shoot

the messenger.

 

Hugs, JoAnn

 

 

 

 

In , " Sara Mandal-Joy "

<sarajoy@m...> wrote:

> Again, an article that has nothing to do with what Dr. Atkin's

books say, which is how to eat a healthy, balanced low carb diet,

yes to help in losing weight if that is important to you, but most

of all to achieve a healthy state of being. The problems described

below have nothing to do with the way of eating described in Dr.

Atkins's books. Nothing at all.

> I'm making such a point of this, because I think it is something

that happens far too often in many realms of health. We assume we

understand dynamics about some condition or remedy or way of health,

and build research or further information gathering based on those

assumptions, without ever fully having studied the original

assumptions.

> I am finding as much close-mindedness in the alternatives area of

health, as in traditional medicine, and it concerns me, greathly.

JoAnn, I am not speaking of you or even to you in this response,

just reacting to the article. I find many of your posts very

valuable and insightful, and appreciate the " gathering " work that

you do. I understand you're putting the information out there for

whatever use it is to various people needing such information. I

simply do know a great deal about atkins, and find these articles to

be completely uninformed about what atkins really is. In terms

of " doing " atkins improperly, along the lines that popular

perception thinks of atkins, yes there is good information and

warning.

> But that has nothing to do with atkins low-carbing as it is

supposed to be done. I would agree with Mary that far too many

people low-carbing are approaching it from a very non-healthful

way. And, yes, some of them fill chatboards with defense of such.

However, there are low carb " lists " dedicated to following the books

as written, and thus to healthful ways of eating.

>

> Please, before you throw something out the window because of what

people believe about it, research from the source what it is you are

looking at, learn for yourself. If all of those of us here were to

apply to our way of life and health in general the assumptions that

the mass public hold, and the research traditional medicine uses to

back up those assumptions, we'd be a sad lot, and in fact would have

no need or desire for such a list as this. One needs to question

popular assumptions about all matters regarding our health,

including our ways of eating as an important aspect of health. Joy

>

>

> -

> JoAnn Guest

>

> Friday, January 23, 2004 12:15 PM

> Another Point of

View -Taken from the Archives

>

>

> " H & M Feld " <ari-@e...>;

> Fri Nov 28, 2003 5:41 pm

> Another Point of View

>

>

> Volume 88 . Number 1 . July 1, 2001

> 2001 The American College of Cardiology

>

> Metabolic effects of high-protein, low-carbohydrate diets

> Margo A. Denke, MD a

> --------------------------------

----

>

> a Division of Endocrinology and Center for Human Nutrition

> University of Texas Southwestern Medical Center at Dallas

> Dallas, Texas, USA

> --------------------------------

----

>

> Address for reprints: Margo A. Denke, MD,

> Center for Human Nutrition,

> The University of Texas

> Southwestern Medical Center at Dallas,

> 5323 Harry Hines Boulevard,

> Dallas, Texas 75390-9052

> E-mail address: mde-@m...

>

> Manuscript received January 16, 2000;

> revised manuscript received January 6, 2001,

> accepted January 6, 2001

> PII S0002-9149(01)01586-7

>

> Weight-losing diets appeal to the growing population of

overweight

> Americans.

> Fad diets promise rapid weight loss, easy weight loss, limited

> restrictions onportion sizes of favorite foods, and above all an

> enhanced sense of well being.

>

> The popularity of fad diets points out the honest promises of

> traditional weight loss diets.

> Traditional weight loss diets promise slow weight loss

> of 0.45 to 0.9 kg/week.

>

> The weight loss is nothing but easy, because portion sizes of

> nearly all foods except low-calorie " free foods " must be

> continuously evaluated and tracked.

>

> Claiming an enhanced sense of well being is hardly

> appropriate for a traditional diet-most patients report

> dissatisfaction from the constant vigilance over dietary intake.

>

> Through discipline and perseverance,traditional weight loss

programs

> try to teach a patient a new lifestyle of healthy eating.

> Unfortunately, 70% of successful weight losers return to their

old

> habits and within 2 years regain at least half of the weight

lost.

>

> These patients typically have little insight into the reasons

why

> the weight was regained,and consider themselves " failures " to

> traditional diet programs. They become prime targets for diets

> promising rapid and easy weight loss.

>

>

> Prototypes of the high-protein, low-carbohydrate diets

> High-protein, low-carbohydrate diets have a long history of

cyclic

> popularity.Greek Olympians ate high meat, low vegetable diets

>2,000

> years ago to improve athletic performance.

>

> Dr. William Harvey recommended a diet prohibiting sweet

> and starchy foods and permitting ad lib consumption of meats for

> patients who needed diuresis.

>

> As the basic understanding of nutrition and essential vitamins

> developed, these diets fell out of favor. They regained

popularity

> in the late 1960s and early 1970s with the publication of the

> Atkins' Diet, Stillman's Diet, The Drinking Man's Diet, the

> Scarsdale Diet, and the Air Force Diet.

>

> The American Medical Association strongly criticized these diets,

[1]

> leading to their submergence on the popular diet trend.

> Resurgence of low carbohydrate diets has been fueled by rising

> obesity and insulin resistance in the general population.

Although

> the Atkins' Diet is the prototype of the low carbohydrate diet,

The

> Sugar Busters Diet,Carbohydrate Addicts Diet, Protein Power

Diet,

> and the Zone Diet are all variations on this common theme.

>

> Several diets promise that, as long as you restrict

carbohydrates,

> you will lose weight and you can eat as much food as you want.

> There may be a kernel of truth to this claim. For some patients,

> high-protein intake suppresses appetite.

> For other patients, ketosis from carbohydrate restriction

suppresses

> appetite.

> Restricting carbohydrate eliminates some popular foods that are

> often consumed in excess such as bread, cereal, soft drinks,

french

> fries, and pizza. By simply excluding carbohydrate foods,

patients

> following the Atkins diet typically consume 500 fewer calories a

> day.

> How low-carbohydrate diets produce initially greater weight loss

> Reducing caloric intake by 500 kcal/day should result in a 0.45-

to

> 0.9-kg weight loss each week.

>

> However, low-carbohydrate, high-protein diets typically produce

a 2-

> to 3-kg weight loss in the first week. This added weight loss is

> not due to the miracle of " switching the body's metabolism over

to

> burning fat stores. "

>

> It is due to a diet-induced diuresis.

>

> When carbohydrate intake is restricted, 2 metabolic processes

occur,

> both of which simultaneously reduce total body water content.

>

> The first process is mobilization of glycogen stores in liver

and

> muscle. Each gram of glycogen is mobilized with approximately 2

g

> of water. The liver stores approximately 100 g of glycogen and

> muscle has 400 g of glycogen.

>

> Mobilization glycogen stores result in a weight loss of

> approximately 1 kg. Patients notice this change as a reduction

in

> symptoms of " bloating " and are very pleased with the effect.

>

> The second process is generation of ketone bodies from

catabolism of

> dietary and endogenous fat.

>

> Ketone bodies are filtered by the kidney as nonreabsorbable

anions.

> Their presence in renal lumenal fluids increase distal sodium

> delivery to the lumen,

> and therefore increase renal sodium and water loss.

>

> In a study comparing an 800-calorie mixed diet with an 800-

calorie

> low-carbohydrate, high fat diet,[5] 10-day weight loss was 4.6

kg on

> the ketogenic diet and 2.8 kg on the mixed diet.

>

> Energy-nitrogen balanced studies documented that the difference

in

> weight lost was all accounted for

> by losses in total body water.

>

> Long-term weight loss is influenced by caloric restriction, not

> carbohydrate restriction

> The diuretic effect of low-carbohydrate intake is limited to the

> first week of the diet.

>

> The remaining weight loss is a function of the laws of energy

> balance.Calories from any source determine the success of

additional

> weightloss.

>

> In the only published study of Atkins diet, patients following

the

> diet reduced caloric intake by 500 kcal/day. The average weight

loss

> was 7.7 kg at 8 weeks, which is no greater than that expected

from

> caloric restriction alone.[6]

>

> The bility of low carbohydrate intake to generate ketones has

been

> touted as a relative avantage for losing weight. However, this

> advantage was not confirmed in a 1-month study comparing

ketogenic

> with nonketogenic hypocaloric diets.[7]

>

> Most comparison studies have evaluated the relative advantages

of

> either a low carbohydrate or low fat hypocaloric diets; some

studies

> found a slight 1- to 3-kg greater weight loss on a low-

carbohydrate

> diet,[8] [9] [10]

> [11] others a slight advantage with a high-carbohydrate diet,

[12]

> but most studies have observed no statistical advantage of a

> low-carbohydrate diet.[13]

>

> [14] [15] [16][17] [18] The preponderance of evidence suggests

that

> as long as caloric intake remains constant,[19] there is no

> intrinsic advantage to cutting carbohydrate intake.[20]

>

> Untoward metabolic effects

> Complications from ketosis

>

> Eucaloric ketogenic diets have been prescribed as part of an

> antiepileptic regimen in children with refractory seizure

disorders.

> Children following these ketogenic diets have higher rates of

> dehydration, constipation, and

> kidney stones. Other reported adverse effects include

> hyperlipidemia, impaired neutrophil function, optic neuropathy,

> osteoporosis, and protein *deficiency*.[21]

>

>

> Because ketogenic diets effect the central " nervous system " , it

has

> been suspected that ketogenic diets may alter cognitive

function.

>

> In a randomized weight loss study comparing a ketogenic with a

> nonketogenic hypocaloric diet,

> subjects consuming the ketogenic diet had impairments in higher

> order " mental processing " and flexibility than those following

the

> nonketogenic

> diet.[7]

>

> Complications from high saturated fat intake

>

> Despite the beneficial effects of weight loss, diets that

promote

> liberal intake of high fat meats and dairy products raise

> cholesterol levels.

>

> In a study 24 subjects following the Atkins'-type 4-week

induction

> diet, then 4 weeks maintenance diet,[6] low-density lipoprotein

> cholesterol levels increased significantly from 127 to 151

mg/dl.

>

> Similar increases in total cholesterol (13%) were reported in a

> study of patients following the Stillman diet.[22]

>

>

> Complications from high fat intake

>

> High fat diets increase free fatty acid flux and circulating

free

> fatty acids.

> Fasting plasma free fatty acids may have a pro-arrhythmic effect

in

> cardiac muscle.

>

> A number of mechanisms have been suggested including apossible

> detergent effect of circulating free fatty acids on cell

membranes

> and

> direct effects of acylcarnitine on cellular ion channels and

> exchangers.

>

>

> Complications from exclusion of fruits, vegetables, and grains

> Because they exclude fruits, vegetables, and grains, low-

> carbohydrate,high-protein diets are deficient in micronutrients.

>

> Children consuming low-carbohydrate ketogenic diets have reduced

> intakes

> of calcium,magnesium, and iron.[21] Two sailors following a

> low-carbohydrate, high-protein hypocaloric diet during an

extended

> voyage developed optic neuropathy from thiamine deficiency.[23]

>

> Although vitamin deficiencies can be circumvented by

> supplemental multivitamins, even supplemented low-carbohydrate

diets

> will still be deficient in a growing number of important,

> biologically

> active phytochemicals present in fruits, vegetables, and grains.

>

>

> Complications from high-protein intake

>

> Increasing the protein content of a diet significantly increases

> glomerular filtration rate.[24] [25] Increases in glomerular

> filtration

> rate are likely explained by increased renal capillary

permeability.

>

> Unfortunately, this compensatory response to the greater

production

> of nitrogen is

> insufficient to clear protein by-products, and blood urea

nitrogen

> levels increase.

>

> High protein diets significantly lower urinary pH by increasing

> titratable acid concentrations.[25] [26] High protein intakes

> provide a

> greater **uric acid** load to the kidney.

>

> Despite increases in urinary uric acid excretion,

> increases in serum uric acid are observed.[6] [26]

>

> Untoward long-term effects

> Development of nephrolithiasis

>

> Hypercalciuria is a risk factor for nephrolithiasis. High-

protein

> diets induce hypercalciuria by several different mechanisms.

> High-protein diets increase glomerular filtration rate and

decrease

> renal tubular reabsorption of calcium.

 

> TABLE 1. Graded Effects of High-Protein Diets on Urinary Calcium

 

> The stone-forming propensity of the hypercalciuria induced by

high-

> protein diets is aggravated by other changes in urine

composition.

>

> A high animal protein diet reduces gastrointestinal alkali

> absorption,

> leading to reduced urinary citrate.[28]

>

> Hyperuricemia and hyperuricosuria are also associated

> with excess intake of animal protein. Animal protein is a rich

> source of

> sulfur-containing amino acids; amino acids have a greater

propensity

> to lower urinary pH.

>

> Adding a carbohydrate restriction to a high-protein diet

exacerbates

> many of these parameters. Low-carbohydrate intake further

reduces

> urinary pH by inducing ketosis.

>

> Limiting the intake of vegetables and fruits further

> reduces urinary citrate by reducing dietary sources of alkali.

>

> Thus, high-protein,low-carbohydrate diets are associated with

> hypercalciuria,hyperuricosuria, and hypocitraturia, which can

all

> contribute to renal calculi formation.

 

> Development of osteoporosis