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TAKE-HOME MEDICAL GRAND ROUNDS POINTS FROM LECTURES BY ARTHUR S. AGATSTON, MD CME Agatston Research Institute, Miami Beach, FL; CLEVELAND CLINIC CREDIT Dr. Agatston, a preventive cardiologist, is author of the South Beach and developed the AND VISITING Agatston calcium score FACULTY

The end of the diet debates? All and carbs are not created equal

■ ABSTRACT HE PUBLIC is confused about what consti- T tutes a : should it be low- The key to healthy eating is choosing “good fats”—foods or low-carb? I believe there is now a consensus high in omega-3 fatty acids and unsaturated fats, and among professionals that the healthiest diet “good carbohydrates”—foods high in fiber and having a consists of “good” fats, “good” carbohydrates, low . The healthiest diet is the , , and lean . Mediterranean type, consisting of lean , , nuts, This article discusses how diet has vegetables, whole fruits, and whole grains. changed from that of early humans, how the modern American diet contains an excess of ■ KEY POINTS refined carbohydrates and leads to insulin resistance and a cycle of overeating, and how The modern American diet is radically different from the to make healthy food choices to achieve one our ancestors ate during millions of years of and better . evolution. It has led to today’s epidemic of , insulin ■ resistance, and . LOW-FAT, HIGH-CARB DIETS UNSUCCESSFUL The low-fat, high-carbohydrate diet recommended by the In the 1980s, Keys et al1 compared industrial American Heart Association leads to insulin resistance. societies and less-industrialized countries and concluded that diets high in fat and low in The high-fat, low-carbohydrate diet advocated by Atkins carbohydrates were to blame for coronary leads to a loss of lean body mass and is dangerously high artery disease. This led to the initial food pyra- in saturated fats. mid and the American Heart Association guidelines, emphasizing predominantly carbo- hydrates and only a small amount of fats. Since then, there has been an upswing in obesity, , and .2,3 An estimated 64% of the US population is classified as overweight or obese,4 and about 40% of Americans older than 40 years have prediabetes. Unfortunately, the American Heart Association adopted its low-fat, high-carbo- hydrate guidelines without subjecting them to a long-term clinical trial. Most trials of these diets have not been able to show weight loss or improved lipid profiles.5,6 The Oslo trial7 did show positive health outcomes from a low- Medical Grand Rounds articles are based on edited transcripts from Heart Center Grand Rounds presentations at The Cleveland Clinic. They are approved by the author but are not peer- fat diet, but results were confounded because reviewed. fish consumption and smoking cessation were

946 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 10 OCTOBER 2005 Downloaded from www.ccjm.org on September 27, 2021. For personal use only. All other uses require permission. greater in the intervention group. the lipid profile. A normal liver efficiently Statin trials may provide the most unbi- metabolizes very-low-density lipoprotein ased evidence for low-fat, high-carbohydrate (VLDL) particles by lipoprotein lipase to large diets. Subjects in placebo groups are usually LDL (pattern A), the less harmful subtype. regularly counseled to eat a traditional Insulin resistance leads to a less efficient fatty National Cholesterol Education Program/ liver, because postprandial clearance of free American Heart Association step 1 diet (total fatty acids from the blood is not as effective, fat ≤ 30% of total calories, ≤ 10% and the fatty acids accumulate in the liver. A of total calories, cholesterol < 300 mg/day). fatty liver creates malformed VLDL particles Typical results initially show a slight decrease that cannot be metabolized well by lipopro- in serum low-density lipoprotein cholesterol tein lipase, resulting in the production of (LDL-C) concentrations, then a return to atherogenic remnants. At the same time, baseline levels. high-density lipoprotein (HDL) particles are altered. These factors tend to decrease the New concepts explain failure total cholesterol level, which helps explain Several important concepts in why people with a serum cholesterol concen- developed only in the past few decades: fiber, tration of less than 200 mg/dL are still at risk. the glycemic index, the metabolic syndrome, trans-fats, the nutrient density of foods, “good The ‘thrifty gene’ theory fats,” and “good carbohydrates.” The “thrifty gene” theory holds that for early These concepts help explain why the low- humans to best survive, the body had to effi- fat, high-carbohydrate diet experiment failed. ciently store fat during times of plenty. We now know that not all low-cholesterol Accumulating fat in the abdomen enabled foods are healthy, especially many “diet” people to still run and hunt fairly well. desserts that are made of processed carbohy- A slower metabolism also conserves ener- drates and trans-fatty acids. gy during famine. Unfortunately for modern dieters trying severe , weight ■ INSULIN RESISTANCE loss is great initially, but lean body mass Thrifty genes declines and lowers metabolism along with fat. make sense When people eat a lot of simple carbohydrates When people start eating their usual diets they crave more soon afterwards, creating a again, they often end up heavier than they if famines vicious circle. Simple carbohydrates cause started. are frequent plasma glucose levels to rise abruptly, trigger- People vary in how rapidly they develop ing insulin secretion. Insulin allows glucose to insulin resistance. Groups such as the Pima enter fat and muscle cells, causing hypo- Indians had subsistence living conditions until glycemia. recently and have very “thrifty” genes. They When blood sugar falls below baseline lev- now have extremely high rates of obesity and els, food cravings start. High-fiber foods, like mellitus, even in children. , cause a smoother rise in blood sugar and a subsequent slower decline, so American diet: does not resume for 4 to 6 hours. A set-up for insulin resistance Other factors heighten the glycemic An over-reliance on fast foods increases the response, making bigger peaks and faster drops likelihood of insulin resistance. The CARDIA in blood sugar. People in middle age tend to (Coronary Artery Risk Development in Young gain visceral fat, which is metabolically differ- Adults) study8 followed more than 3,000 ent from subcutaneous fat, resulting in a larg- young adults for over 15 years. The frequency er glycemic response. In addition, as people of fast food restaurant visits was directly asso- gain weight, visceral adipocytes enlarge, mak- ciated with weight gain and development of ing them metabolically more active and also insulin resistance. harder for insulin to attach to receptors, America is now often exporting its fast enhancing insulin resistance. food—and its health problems—to other coun- Insulin resistance also adversely affects tries. East Indians who have adopted a Western

CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 10 OCTOBER 2005 947 Downloaded from www.ccjm.org on September 27, 2021. For personal use only. All other uses require permission. SOUTH BEACH DIET AGATSTON

diet are developing obesity and diabetes. that ketosis is essential to burn fat: carbohy- People on the islands of Okinawa, Japan, had drates have to be eliminated from the diet to the highest longevity rates recorded in the the point that glycogen stores in the liver and world. When American bases moved in, along muscles become depleted. While the body with fast food, a dramatic increase in obesity does burn fat, to maintain blood sugar, gluco- and diabetes resulted. Their ranking in longevi- neogenesis causes muscle to be used for ener- ty has slipped vis à vis the rest of Japan.9 gy as well. This causes a starvation effect and lowered metabolism, which often leads to yo- GOOD CARBOHYDRATES VS BAD yo . The glycemic index is a measure of the Foster et al18 randomized 63 people with amount that a specific food causes plasma glu- obesity to either an Atkins diet (low-carbohy- cose levels to rise compared with that of an drate, high-fat) or a conventional diet (high- index food, such as glucose or white bread. carbohydrate, low-fat, low-calorie). After 6 Some foods that we traditionally considered months the Atkins dieters lost significantly to consist of complex carbohydrates, like more weight, but differences were no longer potatoes and instant , actually have a significant after 1 year. higher glycemic index than table sugar. The role that fiber and the glycemic index Good fats vs bad fats of foods plays in insulin resistance and weight Another problem with the Atkins diet is that control has been demonstrated in several stud- all fats were regarded as equal, and eating sat- ies.10–13 In a three-way crossover study, Warren urated fats was actually encouraged. We now et al10 randomized 37 children (about one know a lot more about different fats and their third of whom were overweight) to eat break- health risks. fasts consisting of foods having either a high, The Nurses Health study of nearly 85,000 medium, or low glycemic index. They found women over a period of more than 15 years that the higher the glycemic index of the found that those who consumed more trans- breakfast, the more calories they ate for lunch. fat as well as a lower ratio of polyunsaturated Instant rice A review of trials of diets high in “good” fat to saturated fat had a higher risk of dia- has a higher carbohydrates, including fruits, vegetables, and betes, coronary disease, and sudden death.11 whole grains, showed that they consistently The Lyon trial19 randomized patients after glycemic index confer a reduced risk of cardiac events.14 a to either a than sugar Some speculate that the protective effects Mediterranean diet or a prudent Western diet are due to the antioxidants and in and found that those on the Mediterranean fruits and vegetables. But dietary supplements diet had a dramatic reduction in subsequent do not work as well as a diet that includes cardiovascular events, even though differ- whole foods. ences between the two groups in blood lipid Several studies, including the Heart levels and weight were not significant. The Protection study,15 the Heart Outcomes Mediterranean diet included a canola oil Prevention Evaluation (HOPE) trial,16 and spread, which contains alpha-linolenic acid, a the Gruppo Italiano per lo Studio della type of omega-3 fatty acid. This diet is also Sopravvivenza nell’Infarto Miocardico (GISSI) higher in monounsaturated fats, , prevention trial,17 treated some subjects with and fiber than the Western diet, and is lower antioxidant supplements or vitamins, result- in linoleic acid. ing in no benefit against coronary disease, The GISSI trial17 found that subjects who general vascular disease, or . took omega-3 supplements had a reduced risk of coronary events and sudden death. The ■ HIGH-FAT, LOW-CARB DIET benefits were particularly high in patients ALSO UNSUCCESSFUL with left ventricular dysfunction. Omega-3 fatty acids are available through Atkins was a pioneer in promoting the idea plant sources, fish oil, or supplements. Supple- that fat does not necessarily make people fat. ments available on the market appear to be reli- However, one problem is that he believed able and without high levels of mercury.

948 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 10 OCTOBER 2005 Downloaded from www.ccjm.org on September 27, 2021. For personal use only. All other uses require permission. The Nurses Health study20 found that the TABLE 1 more frequently people ate nuts or peanut but- ter, the lower the risk of type 2 diabetes. Nuts Priority changes for diets have an especially high content of good fats. OLD PRIORITIES TODAY’S PRIORITIES Walnuts, in particular, are a good source of omega-3 fatty acids. Food by subtraction Positive nutrition No carbohydrates Good carbohydrates ■ THE SOUTH BEACH DIET: No fats Good fats GOOD FATS, GOOD CARBS Lose weight Lose inches from the waistline The South Beach diet was originally Getting thin Being healthy designed for coronary patients and was intended not only for short-term weight loss but also to help people maintain a lifelong healthy diet. It has several advantages for Phase 3: Lifelong healthy eating patients, including: At this point, dieters have learned which Strategic snacking. Snacking with nuts foods to choose based on their metabolic or low-fat prevents the reactive hypo- responses: brown rice instead of white rice, glycemic dip that commonly occurs in the sweet potatoes instead of white potatoes, late afternoon. Once blood sugar falls, self- whole grain bread instead of white bread, control is very difficult, leading to overeat- whole fruits and vegetables, lean protein such ing. as fish, and the right fats. Simplicity, involving no counting of calo- ries or weighing of foods. Weight loss and an improved lipid profile Flexibility. No fixed ratio of nutrients is We randomized 60 participants to the South required, recognizing that people have differ- Beach diet vs the National Cholesterol ent needs. Young athletes, for example, can Education Program/American Heart Associ- safely eat a lot of protein, which is not recom- ation step II diet (saturated fat < 7% of total Snacking with mended for older patients with calories and cholesterol < 200 mg/day) for 12 nuts prevents and kidney disease. weeks. The South Beach diet resulted in The basic approach has three phases. greater weight loss as well as a significant reactive decrease in the waist-to-hip ratio and serum hypoglycemic Phase 1: Eliminating carbohydrates levels of triglycerides, none of which occurred The first phase, lasting 14 days, involves elim- in the other diet.21 dips inating all starches, including rice, potatoes, Weight loss on the South Beach diet does , baked goods, , sweets, and alcohol. not occur at the same rate for everyone Normal-sized portions of lean meats, eggs, because of genetic differences in metabolic reduced-fat cheese, nonfat , nuts, and rates13 and other factors. I have one patient vegetables are allowed. Rapid weight loss usu- who follows the diet yet remains obese despite ally occurs during this period, but the most an excellent lipid profile. Another patient is important outcome is eliminating cravings for not overweight but has a strong family history sugar that previously resulted from reactive of coronary disease, and despite a low-fat diet hypoglycemia and insulin resistance. and a lot of exercise daily, has a poor lipid pro- file and evidence of coronary artery disease. Phase 2: We often see patients who after a time on Reintroducing good carbohydrates the diet lose weight, improve their lipid pro- Carbohydrates with a favorable glycemic file, and have a normal hemoglobin A1c, but index, including whole grain and cere- are still not satisfied with how they look. I feel als, brown rice, whole wheat pasta, and whole this is a cosmetic problem rather than a med- fruits, are gradually added back into the diet. ical one. They can increase lean body mass This results in a slow weight loss (1–2 pounds through exercise, but not through starvation per week) until the weight goal is reached. dieting, which causes weight to rebound.

CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 10 OCTOBER 2005 949 Downloaded from www.ccjm.org on September 27, 2021. For personal use only. All other uses require permission. SOUTH BEACH DIET AGATSTON

■ CULTURAL CHANGES NEEDED We can all agree on what comprises a healthy diet, but the challenge is in applying Eating habits are heavily ingrained in society. our knowledge. We need to foster new priori- The South Beach diet is essentially a ties in healthy eating (TABLE 1) by educating Mediterranean-type diet. People in Mediter- the public and health professionals, and espe- ranean countries do not eat the way they do cially by targeting children. We also need to because they are on a diet, but because they challenge the food industry to make restau- are surrounded by healthier foods. rant dining and fast food healthier.

■ REFERENCES 1. Keys A, Menotti A, Karvonen MJ, et al. The diet and 15-year death 13. Bouchard C, Tremblay A. Genetic influences on the response of body rate in the seven countries study. Am J Epidemiol 1986; 124:903–915. fat and fat distribution to positive and negative energy balances in 2. Mokdad AH, Bowman BA, Ford ES, Vinicor F, Marks JS, Koplan JP. human identical twins. J Nutr 1997; 127:943S–947S. The continuing epidemics of obesity and diabetes in the United 14. Hu FB, Willett WC. Optimal diets for prevention of coronary heart States. JAMA 2001; 286:1195–1200. disease. JAMA 2002; 288:2569–2578. 3. Ford ES, Giles WH, Dietz WH. Prevalence of the metabolic syndrome 15. Heart Protection Study Collaborative Group. MRC/BHF Heart among US adults: findings from the third National Health and Protection Study of antioxidant supplementation in 20,536 Nutrition Examination Survey. JAMA 2002; 287:356–359. high-risk individuals: a randomised placebo-controlled trial. Lancet 4. National Center for Health Statistics, Centers for Disease Control. 2002; 360:23–33. http://www.cdc.gov/nchs. 16. Lonn E, Bosch J, Yusuf S, et al; HOPE and HOPE-TOO Trial 5. Katan MB, Grundy SM, Willet WC. Should a low-fat, high-carbohy- Investigators. Effects of long-term supplementation on car- drate diet be recommended for everyone? Beyond low-fat diets. N diovascular events and cancer: a randomized controlled trial. JAMA Engl J Med 1997; 337–563–566. 2005; 293:1338–1347. 6. Dreon DM, Fernstrom HA, Williams PT, Krauss RM. A very low-fat 17. Dietary supplementation with n-3 polyunsaturated fatty acids and diet is not associated with improved lipoprotein profiles in men with vitamin E after myocardial infarction: results of the GISSI- a predominance of large, low-density lipoproteins. Am J Clin Nutr Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza 1999; 69:411–418. nell’Infarto Miocardico (erratum in Lancet 2001; 357:642). Lancet 7. Hjermann I, Velve Byre K, Holme I, Leren P. Effect of diet and smok- 1999; 354:447–455. ing intervention on the incidence of coronary heart disease. Report 18. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-car- from the Oslo Study Group of a randomised trial in healthy men. bohydrate diet for obesity. N Engl J Med 2003; 348:2082–2090. Lancet 1981; 2:1303–1310. 19. de Lorgeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. 8. Pereira MA, Kartashov AI, Ebbeling CB, et al. Fast-food habits, weight Mediterranean diet, traditional risk factors, and the rate of cardio- gain, and insulin resistance (the CARDIA study): 15-year prospective vascular complications after myocardial infarction: final report of the analysis (erratum in Lancet 2005; 365:1030). Lancet 2005; 365:36–42. Lyon Diet Heart Study. Circulation 1999; 99:779–785. 9. Onishi N. On U.S. fast food, more Okinawans grow super-sized. New 20. Jiang R, Manson JE, Stampfer MJ, Liu S, Willett WC, Hu FB. and York Times Mar 30, 2004; A4. peanut consumption and risk of type 2 diabetes in women. 10. Warren JM, Henry CJ, Simonite V. Low glycemic index breakfasts and JAMA 2002; 288:2554–2560. reduced food intake in preadolescent children. Pediatrics 2003; 21. Aude YW, Agatston AS, Lopez-Jimenez F, et al. The National 112:e414–e419. Cholesterol Education Program diet vs a diet lower in carbohydrates 11. Hu FB, Manson JE, Stampfer MJ, et al. Diet, lifestyle, and the risk of and higher in protein and monounsaturated fat: a randomized trial. type 2 diabetes mellitus in women. N Engl J Med 2001; 345:790–797. Arch Intern Med 2004; 164:2141–2146. 12. Ludwig DS, Pereira MA, Kroenke CH, et al. , weight gain, and risk factors in young adults. JAMA ADDRESS: Arthur S. Agatston, MD, FACC, Agatston Research Institute, 1999; 282:1539–1546. 4302 Alton Road, Suite 710, Miami Beach, FL 33140.

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