Prediabetes is defined as a condition high risk for developing diabetes. Patient blood sugar levels are higher than normal but not high enough to classify a patient as diabetic. The prevalence of prediabetes is increasing and poses a serious public health problem. However, prediabetes is reversible, and proper diagnosis and management can delay or prevent the onset of diabetes (Mainous et al., 2016). 11.3% of the adult US population has diabetes, and 38% of the adult US population has prediabetes (“National Diabetes Statistics Report”, 2022). While medications also play a role, first line treatment of prediabetes primarily includes lifestyle modifications such as diet and exercise.
Diagnosis of prediabetes often occurs during testing for diabetes. Some patients with prediabetes may experience symptoms, but not all will. Patients with prediabetes should be tested for type 2 diabetes mellitus every one or two years (“Myths about Diabetes”, 2022). Testing involves a 2-hour oral glucose tolerance test which demonstrates impaired fasting glucose and/or an impaired glucose tolerance. Impaired fasting glucose is generally defined as a fasting plasma glucose between 100.8-124.2 mg/dL, and impaired glucose tolerance is defined as plasma glucose values ranging from 140.4-198.0 mg/dL. HbA1c, known as glycosylated hemoglobin, within the rage of 5.7% to 6.4% can also be used to identify individuals with prediabetes (Mainous et al., 2016).
Current guidelines from the American Diabetes Association state that a healthy meal plan for someone with diabetes is the same healthy eating plan for anyone. This means including nutritious foods such as non-starchy vegetables, limiting added sugars, and prioritizing whole foods when possible (“Myths about Diabetes”, 2022). Reducing caloric intake can lead to an improvement in glycemic control though it is not necessarily associated with weight loss (Sénéchal et al., 2014). During a randomized controlled trial with 34 diabetes/pre-diabetes participants, researchers found that a low carbohydrate diet was more effective at reducing HbA1c values at three months compared to a moderate carbohydrate diet (Saslow et al., 2014). Patients with prediabetes/diabetes do not need to completely avoid carbs, but starchy and high-carb foods will raise their blood sugar. One concern is that a low carbohydrate diet results in a higher proportion of calories from fat, which may also be a cause of concern, but researchers did not find significant elevations in LDL with this diet (Saslow et al., 2014). Continuing research should aim to understand how modifying other macronutrients and micronutrients affects blood sugar levels (Sénéchal et al., 2014).
Exercise interventions are also essential for controlling prediabetes. Aerobic exercise is known to have transient effects on postprandial glucose metabolism and skeletal muscle insulin sensitivity (Rynders et al., 2014). Generally, a combination of aerobic and resistance training is recommended for prediabetic control (Sénéchal et al., 2014). One study found that although moderate intensity exercise and high intensity exercise did not have significant differences in improving postprandial insulin sensitivity, high intensity interval exercise may have greater postprandial effects compared to moderate exercise (Rynders et al., 2014). Further research is required to investigate the independent effect of exercise on glycemic control in individuals with prediabetes and understand how to optimize the effects of exercise (Sénéchal et al., 2014).
Ultimately, while it is generally known that dietary and exercise interventions have a significant effect on prediabetes, further research should focus on understanding the independent effects of diet and exercise on individuals with prediabetes. Currently, most patients with prediabetes do not receive adequate care in managing their condition (Mainous et al., 2016). Primary care providers have a large role to play in the prevention of prediabetes/diabetes, and they must be equipped with the proper knowledge and skills to counsel patients.
References
Mainous AG 3rd, Tanner RJ, Baker R. Prediabetes Diagnosis and Treatment in Primary Care. J Am Board Fam Med. 2016;29(2):283-285. doi:10.3122/jabfm.2016.02.150252
Myths about Diabetes. American Diabetes Association. https://www.diabetes.org/tools-support/diabetes-prevention.
National Diabetes Statistics Report. Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/data/statistics-report/index.html.
Rynders CA, Weltman JY, Jiang B, et al. Effects of exercise intensity on postprandial improvement in glucose disposal and insulin sensitivity in prediabetic adults. J Clin Endocrinol Metab. 2014;99(1):220-228. doi:10.1210/jc.2013-2687
Saslow LR, Kim S, Daubenmier JJ, et al. A randomized pilot trial of a moderate carbohydrate diet compared to a very low carbohydrate diet in overweight or obese individuals with type 2 diabetes mellitus or prediabetes. PLoS One. 2014;9(4):e91027. Published 2014 Apr 9. doi:10.1371/journal.pone.0091027
Sénéchal M, Slaght J, Bharti N, Bouchard DR. Independent and combined effect of diet and exercise in adults with prediabetes. Diabetes Metab Syndr Obes. 2014;7:521-529. Published 2014 Oct 31. doi:10.2147/DMSO.S62367