Metabolic Syndrome – Medical Nutritional Therapy Goals
By Carol S. Casey, RD, CDN, LDN
Metabolic Syndrome, a constellation of metabolic risk factors for type 2 diabetes and cardiovascular disease, is one of the fastest growing disease entities in the world. With this being evident, it may be surprising to some that even as early as the late 1930s research and experiments produced the first evidence of this disease (1). It wasn’t until the late 1970s the actual term of Metabolic Syndrome became commonly used in medical terminology. Metabolic Syndrome is also known as Metabolic Syndrome X, Syndrome X, Insulin Resistance Syndrome, Reaven's Syndrome (named for Gerald Reaven), and CHAOS (in Australia) (2). Due to the epidemic of obesity, Metabolic Syndrome has become more prevalent and closely associated with obesity related co-morbidities within the last decade.
Metabolic Syndrome has concurrent grouping of low levels of high-density lipoprotein cholesterol, hyperglycemia, high waist circumference, hypertension, and elevated triglycerides, which is associated with cardiovascular disease often leading to Type 2 diabetes mellitus (3,4). Although it is synonymous with the “insulin resistance syndrome,” not all patients with the Metabolic Syndrome will have insulin resistance (5).
In 2001, the National Cholesterol Education Program (NCEP) developed operational criteria to make a diagnosis of the Metabolic Syndrome based on clinical grounds and commonly used laboratory tests that are frequently carried out in an office practice (6). The importance of the Metabolic Syndrome was further highlighted in 2001 with the approval of an ICD-9 code (277.7) for the Metabolic Syndrome by the National Center for Health Statistics (7). Individuals with at least three of the five criteria listed in Table 1 are identified as having Metabolic Syndrome and are at greater risk for cardiovascular disease (4,8). The five criteria listed in Table 1 appear to have been selected due to their tendency to cluster together and have been long associated with cardiovascular disease (CVD) risk. The fallacy in choosing the numeric upper limits for each criterion is less clear and not derived from outcome data (3). For this reason individual upper limits of each criteria is not the aim of the diagnostic evaluation, but rather the aim is to evaluate the relationship of each criteria and the relationship with insulin resistance and the role of increasing the CVD risk.
Source: Expert Panel on Detection, Evaluation and Treatment of High Blood cholesterol in Adults. Executive summary of the third report of the NCEP on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III); JAMA. 2001; 2486-2497. Complete report available at: http://www.nhilbi.nih.gov
.Waist Circumference is one method and often the easiest of obtain to determine excess adiposity. This criteria is not a consequence of insulin resistance, rather it is lifestyle variable. The combination of physical inactivity and elevated waist circumference has a direct negative effect on insulin-mediated glucose disposal. These two factors alone increase the possibilities of abnormalities and clinical syndromes associated with insulin resistance/compensatory hyperinsulinemia (1). Caveat is not all insulin-resistant individuals are overweight or obese as well as not all overweight or obese individuals are insulin resistant
Impaired Fasting Glucose (IFG) Concentration (also known as FPG or Fasting Plasma Glucose), defined by The American Diabetes Association as 110 to 126 mg/dL (9) and that these individuals are considered prediabetic. Evidence does suggest that the higher the IFG concentration the more likely an individual is to develop Type 2 Diabetes Mellitus. It should be noted that the 2003 American Diabetic Association Expert Committee report reduced the lower IFG/FPG cut off point from 110 mg/dl to 100 mg/dl, in part to make the prevalence of IFG more similar to that of the Impaired Glucose Tolerance (IGT). However, the World Health Organization (WHO) and many other diabetes organizations did not adopt this change. Further clarification is needed to determine if the individual with an elevated IFG provides a particularly effective method to identify the presence of insulin resistance or predictor of CVD risk (1).
The correlation between insulin resistance and essential hypertension and CVD risk is complicated. The relationship between insulin resistance/hyperinsulinemia and blood pressure does seem to indicate that essential hypertensive individuals are insulin resistant and hyperinsulinemic. Further the normtensive first-degree patients with essential hypertension are relatively insulin resistant and hyperinsulinemic in comparison with a matched control group without family history of hypertension. Finally the hyperinsulinemic individual, as a surrogate estimate of insulin resistance, has been shown in studies to predict the future development of essential hypertension. Additionally, other factors of the relationship between blood pressure and the CVD risk individual include electocardiographic evidence of ischemic changes due to these individuals demonstrating glucose intolerance and hyperinsulinemia when compared to individuals whose electrocardiograms are normal (1).
Components of dyslipidemia in the Metabolic Syndrome are the aspects associated most closely with insulin resistance and CVD risk. Low High-Density Lipoprotein (HDL)-C concentration as a predictor of CVD risk has been known for many years. The role of an increase in Triglyceride (TG) concentrations as an individual CVD risk factor certainly exists in the presumption as a component of Metabolic Syndrome. Hypertriglyceridemia is a central aspect of dyslipidemia in of itself associated with insulin resistance/hyperinsulinemia. This presents as another example of the importance in the diagnostic criteria for Metabolic Syndrome (1).
IFG and IGT should not be viewed as clinical entities as diagnostic indicators, rather risk factors for Diabetes Mellitus as well as CVD. IFG and GT are associated with obesity (especially abdominal and visceral obesity), dyslipidemia with high triglycerides and/low HDL cholesterol, and hypertension. Goals must be tailored to each individual while not losing sight of the overall outcome to increase mortality and decrease the co-morbidities associated with Metabolic Syndrome. These goals must encompass a lifestyle change, as well medical nutritional therapy interventions and pharmacological strategies of medications. Structure lifestyle interventions, aimed at increasing physical activity and producing 5-10% loss of body weight, and certain pharmacological agents have been demonstrated to prevent or delay the development of diabetes in people with IGT. Interventions addressed in Table 2 should be the reference guide for dietetic professionals in the medical nutritional therapy management of the Metabolic Syndrome individual. It is imperative that dietetic professionals, working as a key member of the healthcare team, be aware of the intervention objectives in working with the Metabolic Syndrome individual.
Source: extrapolated from Escott-Stump, S. Nutrition and Diagnosis – Related Car. 6th ed. Baltimore, MD: Lippincott Williams & Walters; 2008 (3)
1) Shils, M.E., Shike, M., Ross A.C., Caballero B., and Cousins R.J. Modern Nutrition in Health and Disease, 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2006:1004-1012.
2) Saradis PA, Nisson PM. The metabolic syndrome: a glance at its history. .J Hypertens. 2006 Apr; 24(4):621-6 http://www.ncbi.nlm.nih.gov/pubmed/16531786.
3) Escott-Stump, S. Nutrition and Diagnosis – Related Car. 6th ed. Baltimore, MD: Lippincott Williams & Wolters; 2008:496-499.
4) Niedert, KC, Dorner B. Nutrition Care of the Older Adult, 2nd ed. Chicago, IL: American Dietetic Association 2004:35-40.
5) Cheal KL, Abbasi F, Lamendola C, McLaughlin T, Reaven GM, Ford ES: Relationship to insulin resistance of the adult treatment panel III diagnostic criteria for identification of the metabolic syndrome. Diabetes 53: 1195–1200, 2004.
6) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults: Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 285: 2486–2497, 2001.
7) Reynolds K, Muntner P, Fonseca V: Metabolic Syndrome Underrated or under diagnosed? Diabetes Care: 10.2337/diacare.28.7.1831.
8) National Instituted of Health. Third Report for the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Bethesda MD: National Institutes of Health; 2001. NIH Publication 01-03670.
9) Expert Committee on the Diagnosis and classification of Diabetes Mellitus. Diabetes Care 2002:25 [Suppl 1]: 58-2-8.