From the Guidelines
Glucose intolerance is a condition where the body is unable to regulate blood sugar levels properly, characterized by hyperglycemia not sufficient to meet the diagnostic criteria for diabetes.
Definition and Diagnosis
According to the American Diabetes Association, glucose intolerance can be categorized as either impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), depending on whether it is identified through fasting plasma glucose (FPG) or an oral glucose tolerance test (OGTT) 1, 2.
- IFG: FPG levels between 100 mg/dl (5.6 mmol/l) and 125 mg/dl (6.9 mmol/l)
- IGT: 2-h plasma glucose levels between 140 mg/dl (7.8 mmol/l) and 199 mg/dl (11.0 mmol/l) ### Risk Factors and Complications Both IFG and IGT are risk factors for future diabetes and cardiovascular disease (CVD) 1, 3, 4.
- Modifiable risk factors for abnormal glucose metabolism include overweight and obesity, physical inactivity, and smoking 4.
- Recent studies have shown that modest weight loss and regular physical activity can reduce the rate of progression of IGT to type 2 diabetes 3, 2.
Prevention and Treatment
Lifestyle interventions, such as diet and exercise counseling, have been shown to be effective in reducing the progression to diabetes 3.
- Medications, such as metformin, have also been shown to be effective in reducing progression to diabetes, although generally not as effective as intensive lifestyle interventions 3, 2.
From the Research
Definition of Glucose Intolerance
- Glucose intolerance is a global health concern that encompasses glucose metabolism abnormalities such as impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and type 2 diabetes (T2D) 5.
- It is defined as a state in which there is postprandial hyperglycemia with minimal elevations of fasting plasma glucose 6.
- Impaired glucose tolerance is defined as two-hour glucose levels of 140 to 199 mg per dL on the 75-g oral glucose tolerance test, and impaired fasting glucose is defined as glucose levels of 100 to 125 mg per dL in fasting patients 7.
Clinical Implications
- Glucose intolerance is associated with an increased risk of developing type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) 8, 9.
- Patients with impaired glucose tolerance or impaired fasting glucose have a significant risk of developing diabetes and thus are an important target group for primary prevention 7.
- The main clinical significance of IGT is as a risk factor for type 2 diabetes, with 20-50% of individuals developing type 2 diabetes over 10 years, and as a risk factor for CVD 9.
Risk Factors
- Risk factors for diabetes include family history of diabetes, body mass index greater than 25 kg per m2, sedentary lifestyle, hypertension, dyslipidemia, history of gestational diabetes or large-for-gestational-age infant, and polycystic ovary syndrome 7.
- Determinants of IGT include age, obesity (total and central), family history of type 2 diabetes, physical inactivity, and triglyceride levels 9.
Treatment and Prevention
- The foundation of treatment for IGT, IFG, and the metabolic syndrome is lifestyle modification, including both dietary change and routine exercise 8, 7.
- Consuming a healthy diet, losing weight, quitting smoking, consuming alcohol in moderation, and increasing physical activity can improve glucose tolerance and reduce the risk of T2D 5.
- Pharmacological agents and botanicals can be used to manage glucose intolerance if the implementation of lifestyle changes is challenging, but more research on botanicals is warranted before a definitive recommendation can be made for their use in managing glucose intolerance 5.