Prediabetes,Physical Activity,and Primary Care Providers

“Identification is a vital first step, highlighted by the fact that just 19% of American adults with prediabetes are aware of their condition.”

Diabetes is the eighth leading cause of death in the United States and a major risk factor for several others, including heart disease and stroke. ¹ Absent intervention, more than 70% of the estimated 98 million American adults with prediabetes will ultimately develop type 2 diabetes.^1,2 In most cases, the transition from prediabetes to overt diabetes is gradual, presenting an opportunistic window for early identification and treatment. Underscoring this opportunity, the Centers for Disease Control and Prevention aptly suggests that prediabetes should be regarded as an abbreviation for “prevent diabetes” ³ —that it should be viewed, in other words, as a call to action rather than as a fait accompli. Identification is a vital first step, highlighted by the fact that just 19% of American adults with prediabetes are aware of their condition. Upon identification, prompt action to normalize blood glucose and insulin levels is equally necessary. Although pharmaceutical approaches remain an important component of the arsenal, lifestyle approaches to include modest weight loss and regular physical activity are considered “first-line therapy for prediabetes” given their proven effectiveness in reversing pathologic pathways and preventing diabetic complications. ⁴

In this issue of the journal, Li and colleagues explore how family medicine providers and their patients view prediabetes. The researchers performed their survey in a large, urban, academic practice, which has a direct referral system to a nearby Diabetes Prevention Program. Despite these ostensible benefits, two of three providers reported inadequate time for lifestyle counseling, and three of four endorsed low patient motivation as a barrier to behavioral modification. ⁵ These findings largely replicate those from a survey conducted nearly a decade ago among family medicine physicians across the United States, in which super-majorities cited low patient motivation (83%) and inadequate patient ability (75%) as barriers to lifestyle modification in prediabetes. ⁶ By adding the patient’s perspective to that of their providers, Li and colleagues offer an invaluable insight for population and clinical health promotion. Despite the largely skeptical posture of most providers, the vast majority (96%) of patients with prediabetes were confident they could prevent progression to overt diabetes via diet and physical activity. ⁵ This mismatch is compelling and instructive.

Mending the conflict between provider pessimism and patient optimism requires education of health care providers, specifically in two areas. First, providers should be cognitively convinced that lifestyle modification can effectively reverse prediabetes. Second, they should appreciate how their own health behaviors affect those of their patients. Both topics are worth exploring here in some depth, with an emphasis on physical activity.

Providers and patients alike in Li’s survey were correct to value physical activity as a powerful therapeutic for blood sugar normalization. Unfortunately, even among patients with diagnosed diabetes, adequate physical activity is uncommon. Only 24% of American adults with diabetes report getting at least 150 minutes per week of moderate-to-vigorous aerobic physical activity (MVPA), while 32% report no aerobic activity whatsoever. ¹ Compared with inactive adults in the United States, those who achieve the recommended targets in the Physical Activity Guidelines for Americans, 2nd edition (at least 150 minutes of MVPA and at least 2 days of muscle-strengthening activity per week ⁷ ), have a 53% lower risk of diabetes mortality and 50% lower risk of cardiovascular disease mortality. ⁸

The health benefits of physical activity accrue long before the onset of overt diabetes. Among individuals with prediabetes, routine aerobic physical activity can improve glycated hemoglobin (HbA1C) levels, fasting blood sugar levels, oral glucose tolerance, and body composition. ⁹ Physical activity is therefore a key constituent of nearly all lifestyle programs for prediabetes that have been scientifically evaluated. Because these interventions are usually multifaceted (i.e., they include caloric restriction and psychosocial support in addition to physical activity promotion), the precise contribution of physical activity is unknown. For example, in a recent systematic review of 30 randomized controlled trials of lifestyle modification in prediabetes, only three contained no formal physical activity component. In a meta-analysis of the trials comparing lifestyle and pharmaceutical approaches to prediabetes, the authors concluded that the latter were moderately effective, whereas lifestyle modification was demonstrably more effective. ¹⁰

The National Diabetes Prevention Program—a lifestyle-modification program that targets at least 7% weight loss and at least 150 minutes per week of MVPA—has an exceptionally strong track record. In an early randomized controlled trial of persons with prediabetes, the incidence of diabetes among those in the lifestyle-modification arm was 4.8 per 100 person-years—a 58% lower incidence than persons in the placebo arm and 39% lower incidence that those in the metformin arm, both of which were statistically significant differences. Based on logs maintained by the participants in this trial, 74% of those in the lifestyle-modification arm were achieving the aerobic recommendation at 24 weeks and 58% at their final visit, between 1.8 and 4.6 years after initiation. The key takeaway from this trial for primary care providers was the number needed to treat: Over a three-year period, only 7 persons would need to participate in the lifestyle intervention program to prevent an incident case of diabetes. ¹¹ In a secondary analysis of participants at the 1-year mark, investigators found that participants who failed to achieve the weight loss goal but were adequately physically active had a 44% lower incidence of diabetes than those in the placebo arm. ¹² In light of this corpus of evidence, the U.S. Preventive Services Task Force ¹³ and the American Diabetes Association ¹⁴ recommend that adults with prediabetes participate in at least 150 minutes per week of MVPA.

A mere academic appreciation of the preventive effect of physical activity on diabetes is inadequate for large-scale behavior change across the population. Health care providers should also practice these disease preventive behaviors in their own lives—both for their own well-being and for that of their patients. Studies evaluating providers’ personal health behaviors and their clinical management consistency demonstrate that those who are regularly physically active are more likely to provide physical activity counseling, and their patients are more likely to find the counseling compelling. Authors reviewing this topic noted that a similar relationship has been documented for smoking cessation counseling and vaccination adherence. ¹⁵ Such analogous results for other health behaviors, in addition to the effect size and replicability of these findings, suggest a potentially causal link between provider behaviors, behavioral counseling, and patient responses.

Li and colleagues have provided a tremendous service in conducting this survey and sharing its germane results. Whereas providers in their academic family medicine practice were largely skeptical of their patients’ ability to make necessary lifestyle modifications to prevent diabetes, patients were overwhelmingly confident. To our delight, surveyed patients desired “more assertive and specific … recommendations” and “more aggressive encouragement.” ⁵ These results ought to encourage health care providers who counsel patients with prediabetes that their counseling is both desired and efficacious. It might also inspire providers to achieve the recommended levels of physical activity ⁷ themselves, because their example also matters.

Given strong and consistent evidence for physical activity and dietary change in the reversal of prediabetes, it is now commonplace to see lifestyle approaches emphasized in national guidelines. As a recent review article succinctly summarized: “First-line therapy for prediabetes is lifestyle modification.” ⁴ For nearly 100 million adults in the United States, it is time to ensure this is not an empty slogan but an actual solution.