Family Medicine Residency Program, Mayo Clinic Florida, Jacksonville (Drs. McMullan and Kimsey); Jacksonville Family Medicine Residency Program, Uniformed Services University of Health Sciences, FL (Dr. Smith) mcmullan.stephen@mayo.edu
The authors reported no potential conflict of interest relevant to this article.
The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States government.
Four dietary plans can reduce A1C levels but may differ in long-term outcomes. Intensive lifestyle interventions may even make remission possible.
› Recommend a reduced-calorie diet that is generally plant based and low in carbohydrates as part of the treatment plan for type 2 diabetes. B
› Counsel all patients with type 2 diabetes to engage in physical activity for at least 150 minutes per week at moderate intensity and to add resistance training on at least 2 days to improve glycemic control. B
› Teach patients techniques to reduce stress and improve sleep quality. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence B Inconsistent or limited-quality patient-oriented evidence C Consensus, usual practice, opinion, disease-oriented evidence, case series
References
Type 2 diabetes has been increasing in incidence and prevalence over the past 20 years, with worldwide prevalence estimated at 6.28%.1 The estimated cost of diagnosed diabetes in the United States was $327 billion in 2017; this included direct medical costs and reduced productivity.2 Type 2 diabetes can be prevented in most patients, given that it is a metabolic derangement caused by a complicated interaction between a patient’s genetic predisposition and lifestyle. A consensus statement by the American Academy of Clinical Endocrinologists (AACE) and American College of Endocrinology indicates that the recommended lifestyle modifications for diabetes include medical nutrition therapy with healthy eating patterns, regular physical activity, adequate sleep, behavioral support/counseling, and smoking cessation.3 Evidence shows that adherence to these lifestyle changes alone yields a relative reduction in type 2 diabetes mortality of 57%.4
In the discussion that follows, we review the current guideline recommendations for dietary modifications and physical activity and summarize their effectiveness in the treatment of type 2 diabetes. We also describe practical clinical strategies to promote change in patient behavior, and examine current literature supporting intensive lifestyle changes that, if achieved, may induce disease remission.5
Dietary strategies
Low, or very low, carbohydrate diet
Carbohydrates can affect blood glucose levels in varying degrees depending on their intrinsic properties such as fiber content, sugars, and starches.6 According to the American Diabetes Association’s (ADA) 2019 consensus report,6 the carbohydrate quality that generally should be recommended is high in fiber, vitamins, and minerals, and low in added sugars, fats, and sodium (processed carbohydrates) (TABLE 17-10). A low-carbohydrate diet (LCD) typically has a carbohydrate content < 130 g/d or < 26% of a 2000 kcal/d diet.11 A very low–carbohydrate diet (VLCD) is 20-50 g/d or < 10% of the 2000 kcal/day diet.11
Adherence to lifestyle changes alone yields a relative reduction in type 2 diabetes mortality of 57%.
In a meta-analysis by Goldenberg et al11, the LCD was shown to reduce A1C by 0.47% at 6 months (95% CI, –0.6 to –0.34) and by 0.23% at 12 months when compared with control diets. A review of multiple meta-analyses also showed a significant reduction in A1C especially with VLCD patterns; however, the results waned at the 12-month follow-up.5 In addition, confounding factors were seen when comparing adherence between LCD and VLCD, with patients in the latter group having larger problems with adherence, which decreased the benefit seen in the overall group comparison.11
Very low–carbohydrate/high-fat (ketogenic) diet
Ketogenic diets generally follow a VLCD with the carbohydrate portion set at 5% to 10% of total caloric intake (generally < 30 g/d) and the rest of the calories taken up by protein (typically 1 g/kg/d) and fat (TABLE 17-10).12The fat content recommended is primarily polyunsaturated fat such as olive oil, while saturated fats such as butter and lard (animal fat) should be limited.
A recent meta-analysis by Choi et al12 showed that in overweight or obese patients with type 2 diabetes, the average A1C reduction was 0.62% (95% CI, –0.89 to –0.35) in the ketogenic intervention group. Another meta-analysis showed an even more significant A1C reduction at 1.07% (95% CI, –1.37 to –0.78).13 Concerns have been raised about the ketogenic diet, particularly as it relates to lipid metabolism and cholesterol levels; however, in the 2 referenced meta-analyses, the total cholesterol and triglyceride levels actually declined in the ketogenic intervention groups with minimal effect on LDL-C.12,13 This may alleviate some of the concerns of lipid management with this diet.
Plant-based diet
Popularized by Dr. T. Colin Campbell, a plant-based diet refers to a low-fat, high-fiber, whole-foods diet (whole fruits, vegetables, and naturally occurring carbohydrates, as opposed to processed foods). Examples of this type of diet include the popular vegan diet, which restricts all animal-derived products, and the vegetarian diet, which is generally limited to foods in the plant category with some addition of animal products, such as milk and cheese. Other variations of these diets exist and include other sources of protein (eg, chicken, eggs, or fish) (TABLE 17-10).
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