Maintaining fitness wards off diabetes

By Eleanor McDermid

Young adults who maintain good fitness levels into middle age reduce their risk of developing diabetes, irrespective of changes in their body mass index (BMI), show findings from the CARDIA study.

Lisa Chow (University of Minnesota, Minneapolis, USA) and colleagues took advantage of "the unique design" of the CARDIA study, which assessed its participants' cardiorespiratory fitness at baseline and 7 and 20 years later, along with more regular assessment of prediabetes or diabetes status.

The present analysis therefore "complements and extends the current literature", in which the protective effect of fitness against diabetes is founded on baseline measures.

During the 25 years of follow-up, 44.5% of 4373 participants with initially normal glucose levels developed prediabetes and 11.5% developed diabetes.

As reported in Diabetologia, the team found that each 1 metabolic equivalent increase in cardiorespiratory fitness over time was associated with a small but significant reduction in the risk of developing prediabetes or diabetes, at a hazard ratio of 0.998.

This association was independent of multiple baseline health and socioeconomic variables and, most notably, changes in BMI over time.

However, participants who developed abnormal glucose levels did have a significantly higher BMI at baseline than those who did not, at 25.3 versus 23.2 kg/m² and a larger waist circumference, at 79.9 versus 75.0 cm. They were also older, more likely to be male, of Black race and to smoke, and had higher blood pressure and a less healthy lipid profile.

The study "provides evidence to support the commonly accepted dogma that fitness is beneficial in reducing the risk for prediabetes/diabetes", say Chow et al.

They add: "As this benefit remained significant even when adjusting for BMI, exercise programmes remain critically important for reducing the adverse health impact of prediabetes, diabetes, and their associated complications."

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