The Effects of a Low Carbohydrate Diet on

Health Risk Factors, Weight Loss, and Compliance

Health Promotion and Disease Prevention Symposium

May 6, 2003

Leonard Armstrong, Lily Chiang, Christopher Cox, Grace Kao, Jason

Keune, Carol Lin, William McCoy, Terri McMillan, Gita Mody, Craig Press, Thomas Shane, Celaine So, Benjamin Tollefsen

The February 2003 issue of Men’s Fitness magazine dubbed St. Louis as the nation’s

fifth fattest city, trailing only Houston, Chicago, Detroit, and Philadelphia. The number of

overweight and obese people is not only large in St. Louis but is growing throughout the country.

Although being overweight or obese used to be considered mostly a cosmetic problem, it has

become obvious that weighing too much can cause medical complications. This report aims to

consider the efficacy of a low carbohydrate diet on health promotion and weight loss.

We all have images of what it means to be overweight or obese. Clinically speaking,

though, a person’s weight classification is based on his or her Body Mass Index, or BMI. Body

mass index is calculated as weight in kilograms divided by the square of height in meters

(kg/m2). For an adult, overweight is defined as a BMI greater than or equal to 25.0 kg/m2 and

obese is defined as a BMI greater than or equal to 30.0 kg/m2.

So how bad of a problem is overweight and obesity in the United States? The most

recent data show that the prevalence of obesity in 1999-2000 was 30.5% while the prevalence of

overweight during this time period was 64.5%. Thus, almost two thirds of all Americans are

now considered to be clinically overweight. These values mark significant increases over the

time period from 1988-1994 when the prevalence of obesity was 22.9% and the prevalence of

overweight was 55.9% (Flegal 2002). In the early 1960s, fewer than 1 in 4 Americans were

classified as overweight or obese (Manson 2003).

The fact that the prevalence of overweight and obesity is increasing in the United States

is an important health problem. Excess weight has been shown to be a major risk factor for

premature mortality, cardiovascular disease, type 2 diabetes mellitus, osteoarthritis, some types

of cancers, and many other medical conditions. Furthermore, almost 300,000 American adults

die annually from causes related to obesity. Overweight and obesity is not only a problem for

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the individual, though. The United States health care system currently spends about $51.7

billion on overweight and obesity. This accounts for 5.7% of the total United States health

expenditure. It is also estimated that overweight and obesity accounts for an additional $47.6

billion of indirect costs to society (http://www.niddk.nih.gov/health/nutrit/pubs/statobes.htm).

Together, this means that an almost $100 billion burden is placed on society because of

overweight and obesity.

It is therefore reasonable to examine ways to address this tremendous weight problem in

the United States. The increased prevalence of overweight and obesity is often accredited to

several factors: 1) increased consumption of food (“super-sizing” of meals), 2) greater

consumption of high-fat foods, 3) easily available high-calorie, good-tasting, low-cost foods, 4)

less active or more sedentary lifestyles (Blackburn 2001). While it has been well-shown that

living an active lifestyle, exercising, and monitoring eating habits are helpful in weight loss and

weight control, the merits of individual diets are still up for much debate. The rest of this paper

investigates the efficacy of a low-carbohydrate diet.

A low-carbohydrate diet may be considered based on several theoretical ideas. First, it

has been suggested that high-fat, high-protein, low-carbohydrate diets allow the dieter to feel

more satiated after a meal, thus causing the dieter to eat less. Furthermore, more of the foods

typical people like to eat will fall into this category making it easier for a dieter to follow his or

her plan. These are important considerations since they will most likely increase compliance

with the diet, therefore keeping off lost weight. Another theoretical consideration of a low-

carbohydrate diet is that such a diet would force the body to switch from carbohydrate

metabolism to fat-store metabolism, thus burning accumulated fat and reducing weight.

Similarly, such a diet could decrease insulin spikes after meals thus allowing the body to

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maintain a catabolic state. Finally, a low-carbohydrate diet would allow the dieter to maintain a

proper protein balance despite reduced caloric intake.

Several studies have shown that a diet low in carbohydrates leads to greater weight loss

than the standard, higher carbohydrate diet. The analysis of one low carbohydrate diet shows

that reducing carbohydrate content to less than 70g and restricting caloric intake without

changing protein or fat consumption promotes weight loss. Twenty overweight women

underwent 8 weeks of a low carbohydrate diet (50g/day) with energy restriction (reduced by

2644 kJ/day, from 8384 kJ to 5740 kJ) and lost an average of 5 kg and decreased their BMI by

1.8 kg/m2. In addition to weight loss, investigators measured BMI, percentage body fat, fasting

blood glucose, fasting serum insulin, oral glucose tolerance, free or total IGF, blood pressure,

and cholesterol levels. Improvements in body composition, blood pressure, and blood lipids

without compromising glucose tolerance in moderately overweight women were observed. The

effects of exercise on weight loss or other health factors were not studied. The authors of this

study claim that it demonstrates that a low carbohydrate diet is effective for losing weight and for

decreasing risk factors for cardiovascular disease; however, this conclusion is problematic for

several reasons. The low carbohydrate diet was also a low energy diet, so it is not clear if the

benefits are from reduced carbohydrates, or just from reducing the total energy intake of the

study participants. In addition, while the total cholesterol and LDL cholesterol had decreased by

the end of the 8 weeks, these levels were not significantly different from baseline values obtained

before the trial (Meckling 2002).

In an uncontrolled study by Westman et al. on the effects of a low-carbohydrate diet on

weight loss and cholesterol levels in men and women also showed weight loss, 66% of which

was estimated to be fat mass. Serum bicarbonate levels decreased in patients, but were within

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normal levels. Total cholesterol decreased by 11 mg/dL, LDL decreased by 10 mg/dl, and HDL

rose by 10 mg/dl. Non-HDL cholesterol decreased by 21, and triglycerides decreased 56 mg/dL

over a duration of 24 weeks. The diet composition was 23 +/- 10 g carbohydrates, 115 +/- 29 g

protein, 98+/-27 g fat, and caloric intake was unrestricted; however, mean daily caloric intake

was 1447 +/- 350 kcal. 51% of subjects complied with recommendations to exercise 3 or more

times per week on average during the study duration. While this study does demonstrate weight

loss with a low-carbohydrate diet, it is difficult to interpret its results in the absence of data from

a control group. It is possible that weight loss is due mostly to a decreased caloric intake

(despite the design of the study, which does not restrict caloric intake). Further, skin-fold

measurements were used rather than more precise techniques (Westman 2002).

The well known and popular Atkins’ diet was studied directly by Larosa et al. for 12

weeks. The researchers identified 24 obese (here, 10% above their maximum weight for height

by Metropolitan Life insurance tables) men and women and instructed them to follow the diet

described in Dr. Atkins’ Diet Revolution. The normal diet was followed for 2 weeks, and during

stage 1, study participants were instructed to consume no carbohydrates but were not given

caloric limits. After 4 weeks, stage 2 allowed 5-8 grams of carbohydrates in the diet for 4 more

weeks. After this time, the participants were instructed to resume their normal diet for the last 2

weeks of the study. LDL levels showed a significant increase, especially in women. Changes in

HDL were not significant. Free fatty acids and uric acid also showed a significant increase in

both men and women. Triglycerides were shown to fall significantly in men. The observed

weight loss for the combined groups was 7.7 +/- 0.73 kg; however half of the observed total

weight loss was during the first two weeks of the beginning of the study diet. These results may

be due to the elimination of carbohydrates that ordinarily cause water retention and

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unintentionally limiting calories while limiting carbohydrates. Therefore, this diet may be

effective for short term weight loss (Larosa 1980).

However, in another study with a longer duration of 6 months, overweight were put on

low carbohydrate (35% carbohydrate, 29.9% protein, 35.0% fat) or high carbohydrate (58%

carbohydrate, 20.7% protein, 20.5% fat) diets both with 1200 kcals/day hypocaloric intake. Less

effect on the difference in weight loss was observed between the two groups than in the

previously discussed studies, with the high carbohydrate group losing 4.2 pounds, and the low

carbohydrate group losing 5.4 pounds. The BMI of the low carbohydrate group was reduced by

2.2 kg/m2. The differences in all the other measured outcomes including LDL, HDL and

triglycerides were not significant. Adherence to each diet showed a 25% dropout rate for both

groups. Interestingly, postmenopausal women significantly lost more weight on low

carbohydrate diets than those on high carbohydrate diets. This study also did not consider the

effects of exercise on weight loss (Lean 1997).

The effects of a high-protein diet (≥25% energy intake) have been compared against

other options such as a “balanced” diet, a high-fat diet, or a high-carbohydrate diet. The major

health effects to be examined can be grouped into total weight loss, negative health effects, and

positive health effects. In order for one to contend that replacing one energy substrate with

another will grossly affect weight loss, one must believe that the new substrate is less energy

efficient or causes the organism’s behavior to change so that it uses or requires less energy. The

proponents of a high-protein diet believe that the thermic effect of feeding (TEF) should cause

the body to lose weight. Protein does contribute twice as much to TEF as carbohydrate, though

the studies that have examined this topic have found that in the best case scenario one might be

able to lose 0.09 kg/month as a result of this strategy. Even though this weight loss difference

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was theoretically possible, the studies examined by this group found that no significant weight

loss could be attributed to this substitution of energy substrate. As to behavior modification,

some studies (as reviewed by Eisenstein et al.) did indicate that there was an increase in satiety

from high-protein meals as compared to control meals, though no evidence was presented as to

the long-term stability of this effect. The biggest downfall of high protein diets appears to be

negative effects on the kidneys. Short-term studies indicate that increased protein intake is

associated with increased renal calcium excretion, negative calcium balance, and bone

resorption. In addition, one prospective study of >45,000 men age 40-75 showed that intake of

animal protein was directly associated with risk of symptomatic kidney stone formation

(Eisenstein 2002).

Other studies show that hypocaloric low carbohydrate diets do not result in any

differences in weight loss in comparison to hypocaloric high carbohydrate diets. In one 12 week

study that followed overweight men and women on low carbohydrate (25% carbohydrate, 30%

protein, 45% fat) and high carbohydrate (45% carbohydrate, 29% protein, 26% fat) hypocaloric

(<1200 kcal/day) diets showed choice of diet did not influence weight loss or adipose tissue loss

after 12 weeks. In addition to weight loss, BMI, LDL, HDL, triglycerides, and diet adherence

were measured. Compliance greater than 90% (judging by the weight loss compared to

predicted calorie deficit) was observed for both diets. The difference in the loss of lean body

mass was not statistically significant between the two groups, and similar improvements in

cholesterol, triglycerides, glucose, and glycemia were shown. However, basal insulin fell more

markedly in low carbohydrate diet, which may have been because of the higher monounsaturated

fat content in the low carbohydrate diet than in the high carbohydrate diet. The exercise level

was light to moderate for every patient. Shortcomings of this study are the relatively small

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sample size, small proportion of men, and lack of follow-up after 12 weeks. The authors also

replaced carbohydrates with fat in the low carbohydrate diet without looking at how varying

protein might affect results. Further, authors did not specify whether patients were randomized

to the two diets (Golay 1996).

Another hypocaloric diet study was conducted that randomized obese patients in this case

to low carbohydrate (15%) or high carbohydrate (45%) diet for 6 weeks with 2 hours of exercise

per day. The low carbohydrate diet had higher unsaturated fats compared to the high

carbohydrate diet, and protein content similar for each diet. There was no statistically significant

difference in percentage weight loss, percentage fat loss, or nitrogen loss between the low

carbohydrate and high carbohydrate diets after 6 weeks, and though the drop in fasting plasma

glucose, insulin, cholesterol, triglycerides, and HDL cholesterol was smaller in high

carbohydrate diet, the differences were not statistically significant. These several studies seem to

imply that weight loss is due to hypocaloric diet, not the relative composition of carbohydrates,

fats, and protein in the diets (Golay 2000).

Exercise has significant effects on the weight loss and other health factor results of low

carbohydrate diets. Since previous studies have shown that low-carbohydrate, high-fat diets lead

to an improvement in insulin sensitivity, the effects of a low-carbohydrate, high-fat diet on

insulin sensitivity and intracellular glucose processing in healthy, physically fit young men

without family histories of diabetes was studied over three weeks. The men were instructed to

continue their exercise regimens, and the group included 1 triathlete, 3 long-distance bicyclists, 4

runners, 2 runners/weight lifters. The low carbohydrate diet (8% carbohydrate, 17% protein, 75%

fat) was compared to the standard diet (51% carbohydrate, 14% protein, 35% fat), both with

normal caloric intake of approximately 3500 kcal/day. It was shown that the low carbohydrate

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diet caused a drop in mean fasting serum insulin levels from 36+/-6 to 12+/-2 pmol/L.

However, the mean fasting plasma glucose concentration was unchanged. Although the rate of

disappearance of glucose was not affected, substantial alterations in the routes of intracellular

glucose metabolism were seen. Glucose oxidation dropped under both basal conditions and

insulin infusion, while nonoxidative glucose metabolism increased. On the low carbohydrate

diet, insulin had a decreased ability to decrease net fat oxidation; however, free fatty acid levels

were promptly suppressed by insulin infusion on both diets. Myocyte PDH (pyruvate

dehydrogenase) activity decreased dramatically on low-carbohydrate diet. Insulin-stimulated

glycogen synthase activation was much greater during the low carbohydrate diet. These results

show that aerobic capacity is important in maintaining insulin-stimulated nonoxidative glucose

metabolism during a low carbohydrate diet. Further, in young, physically fit subjects, the

eucaloric substitution of fat for carbohydrates does not uniformly lead to a decrease in overall

insulin sensitivity. In normal individuals, physical conditioning and dietary composition interact

in modulating carbohydrate metabolism (Cutler 1995).

In another study, 23 obese women were randomly assigned to aerobic exercise or no

exercise and to energy restricted low fat (60% carbohydrate, 25% protein, 15% fat )or low

carbohydrate 25% carbohydrate, 25% protein, 50% fat) diets both with reduced caloric intake

(1200kcal/day for non-exercising group) for 12 weeks. Prescribed intakes for subjects assigned

to the exercise groups were increased to compensate for the calculated energy costs of the

exercise sessions. Exercise was found to increase loss of fat tissue as opposed to fat-free tissue

(muscle, bone, etc.). Aerobic exercise significantly enhanced fat loss by 2.7 kg. Slightly higher

weight loss was observed with low carbohydrate compared to low fat diet (10.6 kg vs. 8.1 kg)

but no difference in body composition was seen. It can be suggested that the decrease in the rate

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of weight loss with time found in low-energy diets is because of losses of fat-free body mass,

which could cause reductions in resting metabolism, decreases in postprandial energy

expenditure because of smaller meals, and decreases in the energy cost of movement because of

smaller body size (Racette 1995).

Some studies have shown that the difficulty of complying with the low carbohydrate diet

may reduce the theoretical effectiveness of the diets in practice. Landers et al. describes a study

done on 91 obese patients between the ages of 18 and 55. Each patient was randomly assigned

to one of three dieting groups: low carbohydrate, high protein diet (less than 30g carbohydrate

per day); The Zone Diet (snack of 40 % carbohydrate, 30% protein, 30% fat five times a day); a

conventional diet (reduced calories, 50% carbohydrate, 20% protein, 30% fat). These diets allow

the energy needed to promote weight loss of .45 kg/week. The observed mean weight loss after

12 weeks of dieting was 5.2 kg. There were no significant differences between the different

dieting groups. It is difficult to analyze the results of the study due to the high patient drop out

(49 out of 91 original subjects completed the study), and due to poor diet compliance among the

participants. Following completion of the study, no dieters from the low carbohydrate or high

protein group continued with their diets. Zone dieters generally liked their diet. Conventional

plan dieters felt the experimental diet closely approximated a well-balanced eating plan that

would promote healthy eating habits. In light of these results, the researches recommend that

weight loss instructions be kept simple for patients (Landers 2002).

While a number of studies have attempted to study the effects of a low-carbohydrate diet

on weight loss and other parameters of health, there are many difficulties in drawing definitive

conclusions from these studies. The duration of most studies ranged from several weeks to up to

six months, with little or no long term follow up. Thus, we are left with little information on

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long-term diet adherence, weight loss, cardiovascular health, insulin tolerance, etc. All the

same, some conclusions can be drawn by examining several parameters in combination – body

weight lost, metabolic parameters, body composition, nutritional adequacy, and compliance.

It seems that a hypocaloric diet, regardless of its nutritional breakdown, will result in

weight loss, since it is really the reduction of calories consumed that drives weight loss. The

obvious plan for weight loss, then, would be simply to eat less. The difficulty is in convincing

Americans to eat less and to continue to eat less on a permanent basis.

Numerous studies have shown that high-fat and high-carbohydrate diets can cause

cardiovascular disease and diabetes, respectively, as well as a variety of other health problems.

In low carbohydrate diets, the calories tend to be replaced by proteins, which as discussed above,

can lead to negative effects on the kidneys. Nevertheless, it seems that all forms of weight loss,

regardless of the approach taken, lower blood lipid levels, improve glycemic control, and lower

blood pressure (Freedman 2001).

When losing weight, body composition is important to consider because ideally, one

would lose body fat, rather than lean body mass or some other component. High-fat, low-

carbohydrate ketogenic diets cause a greater loss of body water than body fat at first, resulting in

the regaining of water weight when the diet ends. In the long run, though, all diets result in the

loss of body fat.

Another important factor to look at in choosing a diet is whether or not the restrictions

allow for balanced, nutritionally-adequate meals. High-fat, low-carbohydrate diets are low in

vitamins E, A, thiamin, B6, folate, calcium, magnesium, iron, potassium, and dietary fiber, and

thus require supplementation. Very low fat diets are also nutritionally inadequate, since they are

low in vitamins E, B12, and zinc.

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Finally, the issue of compliance is perhaps the most important, since no diet will be

effective unless people are willing to follow it. As brought up in the study by Landers et al, a

diet with simple guidelines seems to be the easiest for patients to follow. In this respect, a

conventional diet with balanced food groups might be the easiest to maintain. Another major

complaint is that diets which cut calories leave one feeling hungry all the time. Diets high in

protein and fat appear to lead to greater satiety, which could lead to better compliance.

Obviously, there is no simple answer as to which diet is the best. Each diet has

advantages and disadvantages, as well as components that have not yet been adequately research

to draw definitive conclusions about. Perhaps the best recommendation, then, is for patients to

choose their diet on a case by case basis. A patient who complains of feeling hungry all the time

on conventional foods may benefit from a high-protein diet such as the Atkins diet; a patient with

little time to prepare special foods, however, may be best off with a balanced, low-fat diet.

Patients with kidney disease or osteoporosis may want to avoid high protein diets, and patients

with cardiovascular disease may want to avoid substituting fats for carbohydrates. Of course,

there may be other positive and or negative health effects to distinguish the various diets that are

not yet apparent. Finally, there are behavioral factors that are important for all diets regardless of

the nutritional breakdown, such as exercise and behavioral modifications, including self-

weighing. In the end, all diets seem to boil down to calorie restriction, so personal factors may

outweigh any other advantages or disadvantages in maintaining a successful diet.

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References http://www.niddk.nih.gov/health/nutrit/pubs/statobes.htm Blackburn GL, Phillips JC, Morreale S. Physician's guide to popular low-carbohydrate weight-loss diets. Cleveland Clinic Journal of Medicine. Sep 2001; 68(9):761, 765-6, 768-9, 773-4. Bravata DM, Sanders L, Huang J, Krumholz HM, Olkin I, Garnder CD, Bravata DM. Efficacy and Safety of Low-Carbohydrate Diets: A Systematic Review. JAMA. 2003; 289(14):1837-1850. Bray GA. Low-Carbohydrate Diets and Realities of Weight Loss. JAMA. 2003; 289(14):1853-5. Cutler DL, Gray CG, Park SW, Hickman MG, Bell JM, and Kolterman OG. Low Carbohydrate Diet Alters Intracellular Glucose Metabolism But Not Overall Glucose Disposal in Exercise-Trained Subjects. Metabolism. Oct 1995; 44(10):1264-1270. Eisenstein J, Roberts SB, Dallal G, & Saltzman E. High-protein Weight-loss Diets: Are They Safe and Do They Work? A Review of the experimental and epidemiologic data. Nutrition Reviews. July 2002; 60(7):189-200. Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and Trends in Obesity Among US Adults, 1999-2000. JAMA. 2002;288:1723-7. Freedman MR, King J, Kennedy E. Popular Diets: A Scientific Review. Obesity Research. March 2001; 9(Suppl1):1S-39S. Golay A, Eigenheer C, Morel Y, Kujawski P, Lehmann T, de Tonnac N. Weight-loss with low or high carbohydrate diet? International Journal of Obesity & Related Metabolic Disorders: Journal of the International Association for the Study of Obesity. Dec 1996; 20(12):1067-72. Golay A, Allaz AF, Ybarra J, Bianchi P, Saraiva S, Mensi N, Gomis R, de Tonnac N. Similar weight loss with low-energy food combining or balanced diets. International Journal of Obesity & Related Metabolic Disorders: Journal of the International Association for the Study of Obesity. Apr 2002; 24(4):492-6. Hensrud DD. Dietary treatment and long-term weight loss and maintenance in type 2 diabetes. Obesity Research. Nov 2001; 9 Suppl 4:348S-353S. Johnson RK. Frary C. Choose beverages and foods to moderate your intake of sugars: the 2000 dietary guidelines for Americans--what's all the fuss about? Journal of Nutrition. Oct 2001; 31(10):2766S-2771S.

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Klein S, Wadden T, Sugerman HJ. AGA Technical Review on Obesity. Gastroenterology 2002;123:882-932. Landers P, Wolfe MM, Glore S, Guild R, Phillips L. Effect of weight loss plans on body composition and diet duration. Journal - Oklahoma State Medical Association. May 2002; 95(5):329-31. 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 Sep 1980;77(3):264-70 Layman DK, Boileau RA, Erickson DJ, Painter JE, Shiue H, Sather C, Christou DD. A Reduced Ratio of Dietary Carbohydrate to Protein Improves Body Composition and Blood Lipid Profiles during Weight Loss in Adult Women. Journal of Nutrition. 2003; 133:411-417. Lean ME, Han TS, Prvan T, Richmond PR, Avenell A. Weight loss with high and low carbohydrate 1200 kcal diets in free living women. European Journal of Clinical Nutrition. Apr 1997; 51(4):243-8. Manson JE, Bassuk SS. Obesity in the United States: A Fresh Look at Its High Toll. JAMA. 2003;289:229-30. McGuire MT, Wing RR, Klem ML, Hill JO. Behavioral Strategies of Individuals Who Have Maintained Long-Term Weight Losses. Obesity Research. July 1999; 7(4):334-341. Meckling KA, Gauthier M, Grubb R, Sanford J. Effects of a hypocaloric, low-carbohydrate diet on weight loss, blood lipids, blood pressure, glucose tolerance, and body composition in free-living overweight women. Can J Physiol Pharmacol Nov 2002;80(11):1095-105. Parker B, Noakes M, Luscombe N, Clifton P. Effect of a high-protein, high-monounsaturated fat weight loss diet on glycemic control and lipid levels in type 2 diabetes. Diabetes Care. 2002; 25(3):425-30. Racette SB, Schoeller DA, Kushner RF, Neil KM, Herling-Iaffaldano K. Effects of aerobic exercise and dietary carbohydrate on energy expenditure and body composition during weight reduction in obese women. American Journal of Clinical Nutrition. Mar 1995; 61(3):486-94. Skov AR, Toubro S, Ronn B, Holm L, Astrup A. Randomized trial on protein versus carbohydrate in ad libitum fat reduced diet for the treatment of obesity. International Journal of Obesity & Related Metabolic Disorders: Journal of the International Association for the Study of Obesity. May 1999; 23(5):528-36. St Jeor ST. Howard BV. Prewitt TE. Bovee V. Bazzarre T. Eckel RH. Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association.

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Dietary protein and weight reduction: a statement for healthcare professionals from the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation. 104(15):1869-74, Oct 9 2001. Ullrich IH, Peters PJ, Albrink MJ. Effect of Low-Carbohydrate Diets High in Either Fat or Protein on Thyroid Function, Plasma Insulin, Glucose, and Triglycerides in Healthy Young Adults. Journal of the American College of Nutrition. 1985; 4:451-459. Westman EC, Yancy WS, Edman JS, Tomlin KF, Perkins CE. Effect of a 6-month adherence to a very low carbohydrate diet program. American Journal of Medicine. 2002;113(1):30-36.

The Effects of a Low Carbohydrate Diet The Effects of a Low Carbohydrate Diet on Health Risk Factors, Weight Loss and on Health Risk Factors, Weight Loss and

ComplianceCompliance

Health Promotion and Disease Health Promotion and Disease Prevention Symposium Prevention Symposium

May 6, 2003May 6, 2003

Defining Obesity Defining Obesity

BMI is kg/mBMI is kg/m22

Normal is between 18 and 24.Normal is between 18 and 24.Overweight is 25 kg/mOverweight is 25 kg/m22 or greater.or greater.Obese is 30 kg/mObese is 30 kg/m22 or greater.or greater.

Major increase in obesity over the past 40 Major increase in obesity over the past 40 years years

1960’s <25% obese or overweight1960’s <25% obese or overweight2000 64.5% are obese or overweight2000 64.5% are obese or overweight

Why do we care? Why do we care?

CoCo--morbiditymorbidityCostCostClinical ObstaclesClinical Obstacles

Dieting Dieting

Fad dietsFad dietsWeight loss programsWeight loss programs“Clinically proven” popular diets“Clinically proven” popular diets

Atkins DietAtkins DietZone DietZone Diet

Investigating ObesityInvestigating ObesityBMIBMIBody Fat %Body Fat %Fasting blood glucoseFasting blood glucoseSerum insulinSerum insulinOral glucose toleranceOral glucose toleranceFree and total IGFFree and total IGFBPBPCholesterol (lipid profile: HDL/LDL)Cholesterol (lipid profile: HDL/LDL)ComplianceCompliance

Study DesignStudy Design

DurationDurationPatient PopulationPatient PopulationFollowFollow--upup

ExerciseExerciseControlControlTotal CaloriesTotal Calories

ComplianceCompliance

Restricted diet Restricted diet DropDrop--outsoutsExercise regimensExercise regimensInpatient vs. Outpatient studiesInpatient vs. Outpatient studies

Problems with StudiesProblems with Studies

Controlled vs. UnControlled vs. Un--controlled controlled Comparison Comparison Compliance and enrollmentCompliance and enrollmentMethods and measurementsMethods and measurementsSample sizeSample sizeDuration of studyDuration of study

So, what about Atkins?So, what about Atkins?

Study Design:Study Design:Weeks 1Weeks 1--2: normal diet2: normal dietWeeks 3Weeks 3--6: no 6: no CHOsCHOs, no caloric limit in , no caloric limit in other categoriesother categoriesWeeks 7Weeks 7--9: limit 59: limit 5--8 grams of 8 grams of CHOsCHOsper day, no limits in other categoriesper day, no limits in other categoriesWeeks 10Weeks 10--12: resume normal diet12: resume normal diet

Results Results

LDL levels increased significantly, HDL LDL levels increased significantly, HDL levels did not change significantlylevels did not change significantlyFFAsFFAs increased significantlyincreased significantlyTriglycerides fell significantly in menTriglycerides fell significantly in menObserved weight loss: 16.94 +/Observed weight loss: 16.94 +/-- 1.61 1.61 lbs, approximately half of this weight lbs, approximately half of this weight loss occurred during the initial 2 weeksloss occurred during the initial 2 weeks

Problems with studyProblems with study

Small sample sizeSmall sample sizeIncomplete measurement of endpointsIncomplete measurement of endpointsWeight loss attributed to?Weight loss attributed to?Short followShort follow--upupComplianceCompliance

Authors’ favorite diet:Authors’ favorite diet:Random AssignmentRandom AssignmentCompare 3 groups:Compare 3 groups:

Low calorie (unrestricted content)Low calorie (unrestricted content)low low carbcarb/ high protein and fat/ high protein and fatlow fat/ high low fat/ high carbcarb and proteinand protein

Large sample sizeLarge sample sizeJournalJournalMonitor compliance Monitor compliance

plasma glucose plasma glucose urine nitrogenurine nitrogen

Conclusion Conclusion

Weight loss: caloric output > caloric intake Weight loss: caloric output > caloric intake No agreement on “the best” dietNo agreement on “the best” diet

Low Low carbcarb diets diets satiation with low calorie satiation with low calorie intake (intake (Eisenstein et al, 2002)Eisenstein et al, 2002)

Diet must be tailored to each patientDiet must be tailored to each patient