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Address correspondence to: Brenda M. Davy, PhD, RD, Department of Human Nutrition, Foods and Exercise, 221 Wallace Hall (0430), Virginia Tech, Blacksburg, VA 24061
Centers for Disease Control and Prevention National diabetes fact sheet: National estimates and general information on diabetes and prediabetes in the United States.
The onset of type 2 diabetes is gradual, with most individuals progressing through a state of prediabetes, which is defined as one or more of the following: impaired fasting glucose (IFG, plasma glucose of 100 to 125 mg/dL [5.6 to 6.9 mmol/L]), impaired glucose tolerance (IGT, plasma glucose of 140 to 199 mg/dL [7.8 to 11.0 mmol/L] 2 hours after an oral load of 75 g dextrose), or hemoglobin A1c 5.7% to 6.4%.
According to a study of a nationally representative sample (n=1,547), an estimated 35% of the United States population has prediabetes: 19% have IFG only, 5% have IGT only, and 10% have both IFG and IGT.
Although individuals can spend years in a prediabetes stage, an expert American Diabetes Association (ADA) panel estimated that up to 70% of individuals with prediabetes will eventually progress to type 2 diabetes.
However, not all individuals with prediabetes progress at the same rate. A meta-analysis of prospective cohort studies showed that the annual incidence of diabetes in people with IGT, IFG, or both was 6.1%, 7.0%, and 14.0%, respectively.
Annual incidence and relative risk of diabetes in people with various categories of dysglycemia: A systematic overview and meta-analysis of prospective studies.
The diagnosis of prediabetes presents health care providers with an opportunity to identify patients at increased risk for type 2 diabetes and to implement interventions that can delay or prevent type 2 diabetes and its complications.
Unfortunately, this opportunity is often unrecognized; an analysis of a nationally representative sample of patients with prediabetes (n=584) concluded that only 31.7% had been counseled about exercise, 33.4% about diet, and 25.9% about both exercise and diet by a physician or other health professional.
Reduction of diabetes risk in routine clinical practice: are physical activity and nutrition interventions feasible and are the outcomes from reference trials replicable? A systematic review and meta-analysis.
However, individuals who have been counseled by their health care provider to adopt a healthy lifestyle reported greater adherence to weight control and diet modification and had lower low-density lipoprotein (LDL) cholesterol, lower body mass index (BMI), and higher high-density lipoprotein (HDL) cholesterol.
Still, it is unclear whether counseling sessions by a primary care provider in the outpatient setting are correlated with improvements in fasting plasma glucose in patients with prediabetes compared with similar patients who have not been counseled. Although some evidence suggests that lifestyle counseling may be associated with self-reported changes in lifestyle behavior in overweight and obese adults with prediabetes and diabetes,
other data suggest that lifestyle intervention programs that have been implemented in the outpatient health care setting have had an insignificant impact on fasting plasma glucose.
Reduction of diabetes risk in routine clinical practice: are physical activity and nutrition interventions feasible and are the outcomes from reference trials replicable? A systematic review and meta-analysis.
Given the high prevalence of prediabetes, it is important to understand the basic underlying pathophysiology and how lifestyle interventions can be implemented in the clinical setting to reduce a patient's risk for progressing to type 2 diabetes.
Pathophysiology of Prediabetes
The same pathophysiologic defects lie at the heart of both IFG and IGT: beta cell dysfunction and insulin resistance. In both IFG and IGT, glucose-stimulated insulin secretion is impaired.
It is possible that diet may affect individuals with IGT and IFG differently. An investigation of individuals (n=5,824; age 30 to 60 years) in the Inter99 study, a randomized intervention study of participants randomly sampled from a specific region of Denmark, found that individuals with diets that routinely included pâté, mayonnaise salads, red meat, potatoes, lard, and/or butter developed worsening oral glucose tolerance, but no change in fasting plasma glucose concentrations was observed over a 5-year period.
Pathophysiology and aetiology of impaired fasting glycaemia and impaired glucose tolerance: Does it matter for prevention and treatment of type 2 diabetes?.
Nevertheless, although there are distinct differences in the pathophysiology of IFG and IGT, no prospective study has looked at whether dietary interventions have different impacts on oral glucose tolerance vs fasting plasma glucose concentrations.
Diet composition can affect insulin sensitivity and beta cell function. Diet-induced weight loss improves insulin sensitivity as well as beta-cell function.
Both energy-restrictive low-fat and low-carbohydrate diets improve hepatic insulin sensitivity and decrease hepatic glucose production with as little as a 2% weight loss, and improve skeletal muscle insulin sensitivity after a 7% weight loss.
A diet rich in saturated fatty acids (14%, 17%, and 6% total energy from monounsaturated, saturated, and polyunsaturated fatty acids, respectively) impairs insulin sensitivity, whereas a diet rich in monounsaturated fatty acids (23%, 8%, and 6% total energy from monounsaturated, saturated, and polyunsaturated fatty acids, respectively) does not seem to alter insulin sensitivity.
However, the relationship between consumption of low-glycemic-index foods and plasma glucose concentration is complex and is altered by the protein and fat composition of a meal, preparation and processing of the food items, prior food intake, fasting or preprandial plasma glucose levels, and degree of insulin resistance.
The risk factors for prediabetes are the same as those for type 2 diabetes. The ADA recommends testing asymptomatic adults for type 2 diabetes if they meet any of the criteria (Figure) that indicate increased risk for type 2 diabetes.
The following case presentation illustrates the importance of recognizing prediabetes and identifies lifestyle modifications that can be used to treat prediabetes in clinical settings. The assessment, intervention, monitoring, and evaluation were done in an outpatient clinic setting by a medical student/research assistant trained to conduct dietary assessments. The case study was conducted and prepared in accordance with the Health Insurance Portability and Accountability Act.
Patient Profile
JS is a 51-year-old, overweight (BMI=28.9), nonsmoking white man treated for hyperlipidemia and hypertension for the past 11 years. His clinical data are reported in the Table. On an annual outpatient visit and physical exam in January of 2011, his systolic blood pressure was 140 mm Hg despite being treated with lisinopril (20 mg/day). His labs were noteworthy for an impaired fasting serum glucose of 112 mg/dL (6.22 mmol/L) and an LDL cholesterol of 98 mg/dL (2.54 mmol/L), which was being controlled by simvastatin (20 mg/day). JS reported that his job required frequent travel and overnight stays at hotels and that he consequently often ate meals prepared outside of the house. He felt that his poor diet and exercise habits had contributed to his now elevated fasting glucose concentration, his overweight status, and his chronic hypertension and hyperlipidemia. In July 2011, the patient reported a desire to make lifestyle changes.
TablePre-interventional and post-interventional laboratory and 24-hour dietary recall results
24-hour dietary recall results are compared with National Cholesterol Education Program (NCEP) and individualized dietary recommendations. Nutrition diagnostic label numbers are presented for some nutrients based on discrepancies between reported nutrient intakes and NCEP recommendations.
from clinical encounters with a 51-year-old patient with prediabetes, hyperlipidemia, and hypertension
To convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555. To convert mmol/L glucose to mg/dL, multiply mmol/L by 18.0. Glucose of 108 mg/dL=6.0 mmol/L.
To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
To convert mg/dL triglyceride to mmol/L, multiply mg/dL by 0.0113. To convert mmol/L triglyceride to mg/dL, multiply mmol/L by 88.6. Triglyceride of 159 mg/dL=1.80 mmol/L.
Reported fiber intake meets NCEP but not American Diabetes Association fiber intake recommendation of 14 g of fiber per 1,000 kcal for type 2 diabetes mellitus prevention.10
24
Sugars, g
133
Protein
136 g (25%)
15%
110 g (24.8%)
a 24-hour dietary recall results are compared with National Cholesterol Education Program (NCEP) and individualized dietary recommendations. Nutrition diagnostic label numbers are presented for some nutrients based on discrepancies between reported nutrient intakes and NCEP recommendations.
b To convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555. To convert mmol/L glucose to mg/dL, multiply mmol/L by 18.0. Glucose of 108 mg/dL=6.0 mmol/L.
c Values not available.
d To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
e LDL=low-density lipoprotein.
f HDL=high-density lipoprotein.
g To convert mg/dL triglyceride to mmol/L, multiply mg/dL by 0.0113. To convert mmol/L triglyceride to mg/dL, multiply mmol/L by 88.6. Triglyceride of 159 mg/dL=1.80 mmol/L.
h BMI=body mass index.
i As evidenced by observed weight gain from December 2009 to January 2011.
j Percentage of total energy.
k NCEP guidelines indicate that trans fats should be kept low but do not include a quantitative recommendation.
l Reported fiber intake meets NCEP but not American Diabetes Association fiber intake recommendation of 14 g of fiber per 1,000 kcal for type 2 diabetes mellitus prevention.
A dietary assessment and 24-hour dietary recall was done for JS on July 19, 2011; these data along with the National Heart, Lung, and Blood Institute's National Cholesterol Education Program (NCEP) recommendations are reported in the Table. JS's intake of fat, saturated fat, dietary cholesterol, sodium, and protein exceeded NCEP recommendations for hyperlipidemic adults by 1.6%, 1.5%, 264%, 154%, and 10%, respectively.
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) final report.
and his carbohydrate intake was less than NCEP recommendations.
JS reported that his physical activity (approximately 15 min/day) consisted of walking from his car to his destination. Based on JS's height, weight, age, and sedentary physical activity level, his total estimated energy requirement was 2,273 kcal/day, per the Mifflin-St Jeor equation
Based on the assessment, and considering the nutrition diagnostic labels (included in parentheses) listed for specific nutrient discrepancies between reported intakes compared with NCEP recommendations, the following Nutrition Diagnostic Statements were developed:
•
Overweight (NC-3.3) related to excessive energy intake and physical inactivity as evidenced by a BMI more than 25.
•
Undesirable food choices (NB-1.7) related to a food and knowledge deficit as evidenced by excessive intake of trans fat, saturated fat, dietary cholesterol, sodium, and protein; elevated fasting glucose concentration; observed weight gain; BMI; hypertension; and hyperlipidemia.
•
Physical inactivity (NB-2.1) related to perceived lack of time for exercise as evidenced by client history.
Intervention
The intervention was done on July 22, 2011. JS was advised to reduce his energy consumption by 500 kcal per day, reduce sodium intake, and increase consumption of fiber-rich foods (see Table; comprehensive nutrition education, E-2). JS reported a preference for fat-rich foods over foods higher in carbohydrates, so he was advised to make modest reductions of both macronutrients to reduce energy intake. JS was advised to substitute water for sugar-sweetened beverages. To increase fiber intake, he was advised to choose whole fruits over the fruit juices that he had been consuming. JS was also advised to reduce his saturated fat consumption by choosing leaner meats and low-fat cheeses and substituting oils for butter. In addition, JS was advised to minimize consumption of foods that contain trans fats. With regard to problem-solving strategies, it was suggested that JS prepare breakfasts, snacks, and lunches for his trips (nutrition counseling, C-1), which would be lower in energy, saturated fat, and sodium and higher in fiber than meals that he would otherwise consume while traveling. Another strategy to make better food choices was to dine at restaurants that report nutritional information. JS was also educated about portion sizes and making healthier food choices in scenarios when nutritional information was not reported. In addition, JS was advised to engage in 150 minutes of moderate intensity physical activity of his choice each week. He expressed interest in adding walking and resistance training to his current physical activity regimen. He was encouraged to pursue these activities but advised to seek professional instruction before pursuing a resistance-training program. JS was counseled that the recommended changes in diet and physical activity should become a permanent part of his lifestyle.
Monitoring and Evaluation
According to Academy of Nutrition and Dietetics Nutrition Care Manual guidelines, lifestyle interventions can be monitored by all of the following: client food and physical activity logs, anthropometric measurements, biochemical data, client questionnaires, and/or telephone or mail communications with the client.
The ADA recommends at least annual monitoring of individuals with prediabetes for the development of diabetes, which can be done by measuring fasting plasma glucose, the 2-hour value in the 75-g oral glucose tolerance test, or hemoglobin A1c.
Changes in body weight and biochemical data were used to monitor JS; however, monitoring would have been more comprehensive if it had included a postinterventional 24-hour dietary recall.
The postintervention data are reported in the Table. JS's body weight decreased 3.2 kg (−3.4%). This represents an approximate 51% reduction in type 2 diabetes risk based on a study of patients with prediabetes (n=1,079), which determined that for every kilogram of weight lost, there was a 16% reduction in type 2 diabetes risk, adjusted for both diet and activity.
JS's fasting plasma glucose decreased from 112 mg/dL (6.216 mmol/L) to 100 mg/dL (5.550 mmol/L) over the 11-month period, which is clinically significant based on results of an investigation of individuals with prediabetes (n=5,452) that reported a threefold greater progression to type 2 diabetes over a 2- to 11-year period among those with a fasting glucose concentration ranging 110 to 125 mg/dL (6.105 to 6.938 mmol/L) compared with those in the 100 to 109 mg/dL (5.550 to 6.045 mmol/L) range.
There was an approximate 18% reduction in LDL cholesterol, from 98 mg/dL (2.538 mmol/L) to 80 mg/dL (2.072 mmol/L). However, it is uncertain whether reductions of LDL cholesterol within the NCEP's optimal goal range of less than 100 mg/dL (<2.590 mmol/L) result in an additional reduction in cardiovascular disease risk in individuals like JS who are at moderate risk for and have no history of coronary heart disease.
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) final report.
However, there was an increase in serum triglycerides from 142 mg/dL (1.605 mmol/L) to 160 mg/dL (1.808 mmol/L) that was significant because it brought JS's serum triglycerides into NCEP's borderline-high triglyceride category (150 to 199 mg/dL [1.695 to 2.249 mmol/L]).
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) final report.
There was relatively little change in blood pressure and HDL cholesterol. A telephone follow-up at 1-year post-intervention (July 20, 2012) indicated that JS was still adhering to dietary recommendations, was still participating in resistance training and aerobic exercise 3 days per week, was satisfied with his progress, and did not currently desire additional assistance.
Discussion
Lifestyle intervention is recommended for individuals with prediabetes to prevent or delay the onset of type 2 diabetes, postpone pharmacologic treatment, preserve beta cell function, and reduce the likelihood of microvascular and cardiovascular complications.
Long-term effects of a lifestyle intervention on weight and cardiovascular risk factors in individuals with type 2 diabetes mellitus: Four-year results of the Look AHEAD trial.
Thus, when developing an intervention for a patient with prediabetes, comprehensive lifestyle change should be recommended to most effectively achieve weight loss and subsequent reduction in type 2 diabetes risk.
A meta-analysis of 10 prospective cohort studies including 301,221 participants and 9,367 incident cases showed that moderate-intensity activity for at least 150 minutes per week reduces the risk of developing type 2 diabetes in individuals with IGT or IFG.
Consistent with these findings, the ADA recommends that individuals with prediabetes engage in 150 minutes of moderate-intensity physical activity per week.
which is relevant to this clinical case. In addition, the ADA recommends that individuals with type 2 diabetes engage in resistance training three times per week.
JS was encouraged to engage in resistance training based on these recommendations, which are supported by research that suggests that resistance training may improve insulin sensitivity and prevent the onset of type 2 diabetes with advancing age.
These recommendations are consistent with the NCEP recommendations (see Table). Accordingly, recommendations for JS included reduction of energy intake to 500 kcal less than his daily estimated energy requirement of 2,273 kcal, reduction of saturated fat to less than 7% of total energy, and minimization of energy from trans fat. The reduction in saturated fat and trans fat is consistent with evidence that reducing saturated fat intake decreases LDL cholesterol and minimizing trans fat intake increases HDL cholesterol and decreases LDL cholesterol,
which is important for individuals who require statins to control LDL cholesterol levels. Because of this patient's hypertension, a reduction in sodium intake to 2.4 g per day was recommended based on guidelines from the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.
and is supported by a meta-analysis of several studies that associate sugar-sweetened beverage consumption with an increased risk for metabolic syndrome and type 2 diabetes.
Finally, although it was recommended that JS reduce his total energy intake, the relative proportions of fat and carbohydrates were kept at a level that was preferred by JS because the optimal macronutrient distribution of weight-loss diets has not been established.
The clinical intervention accomplished the primary goal of reducing JS's fasting blood glucose, which may be attributable to weight loss, dietary changes, increased physical activity, and/or resistance training. The intervention also reduced JS's LDL cholesterol, which is possibly attributable to weight loss,
The patient in this study presented with IFG and an unknown oral glucose tolerance status. Although there is evidence suggesting a difference in the pathophysiology of IFG vs IGT, clinical guidelines do not suggest testing for both fasting plasma glucose and oral glucose tolerance, and the IFG vs IGT status of a patient does not currently alter treatment. Therefore, additional research is warranted to determine whether certain dietary strategies are more effective in treating patients IFG only vs patients with both IFG and IGT.
References
Centers for Disease Control and Prevention
National diabetes fact sheet: National estimates and general information on diabetes and prediabetes in the United States.
Annual incidence and relative risk of diabetes in people with various categories of dysglycemia: A systematic overview and meta-analysis of prospective studies.
Reduction of diabetes risk in routine clinical practice: are physical activity and nutrition interventions feasible and are the outcomes from reference trials replicable?.
Pathophysiology and aetiology of impaired fasting glycaemia and impaired glucose tolerance: Does it matter for prevention and treatment of type 2 diabetes?.
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) final report.
Long-term effects of a lifestyle intervention on weight and cardiovascular risk factors in individuals with type 2 diabetes mellitus: Four-year results of the Look AHEAD trial.