Studies Define Type 2 Diabetes Risk Factors
The risk of developing type 2 diabetes in women is significantly increased as a result of either low cardiorespiratory fitness or higher Body Mass Index (BMI), and a combination of the two increases the risk the most, according to a long-term study presented today at the 55th Annual Meeting of the American College of Sports Medicine (ACSM). An independent and combined association among the two health factors was identified in the study of more than 6,200 women over the course of 17 years.
A protective effect of cardiorespiratory fitness was observed in women who were overweight or obese, but it did not altogether eliminate the increased risk of developing type 2 diabetes in these groups. These findings show that it is important for women to be as active and fit as possible, as well as to maintain a healthy weight to decrease their risk of this chronic disease.
"Physical activity is one of the most important strategies to managing, and in some cases, preventing type 2 diabetes," said Steven P. Hooker, Ph.D. FACSM, lead author of the study. "The incidence of type 2 diabetes is growing swiftly, and across genders and ages. The more we learn about the factors that impact the onset of the disease, and their impact jointly and separately, the more tools we will have to help people manage and prevent the condition."
In the study, the thousands of middle-aged women were enrolled between 1971 and 2004 when free of baseline cardiovascular disease, cancer, and diabetes. At that time, they received a preventive medical examination, during which they completed a maximal treadmill exercise test to define their level of cardiorespiratory fitness. Their health and family history was recorded, as well as other variables including cholesterol, smoking and alcohol intake.
During the years of follow-up, 143 cases of type 2 diabetes occurred. In the combined analyses, overweight/obese unfit (lowest third of cardiorespiratory fitness) women had significantly increased risk of diabetes compared with normal weight fit (upper two thirds of cardiorespiratory fitness) women. The least-fit had a three-fold higher diabetes risk compared to the most fit, while those with the highest BMI scores had a six-fold higher diabetes risk compared to those with lowest numbers.
"One of the more remarkable findings is that a mild to moderate level of aerobic fitness was associated with a substantially reduced risk of diabetes in these women," stated Hooker. "These levels of fitness can be achieved by most women by simply walking briskly for 30 minutes 5 days per week. This amount of regular physical activity will also play an important role in maintaining a healthy body weight, further lowering the risk of diabetes."
Type 2 Diabetes in Adolescents
Research presented at the meeting sheds new information on the impact of type 2 diabetes in youth. In one study, researchers found that youth with type 2 diabetes exhibit low levels of cardiorespiratory fitness and the majority do not participate in adequate amounts of habitual physical activity. The data contribute to what is known about reduced fitness and a sedentary lifestyle as components to the pathophysiology of type 2 diabetes among youth.
"Type 2 diabetes used to be generally called 'adult-onset' diabetes, and its rise in youth has clearly redefined the incidence and risk of the condition wholly," said Melissa Spezia Faulkner, DSN, R.N., principal investigator of this research series. "We need to assess whether changes in fitness and/or activity over time impact diabetes progression or improvement in youth."
The study involved 40 adolescents with type 2 diabetes, and measured their fitness using a cycle exercise tests and self-reported physical activity levels. Collectively, the participants were markedly overweight. After controlling for BMI, boys exhibited significantly higher fitness levels compared to girls, while reported physical activity was not significantly different between genders. None of the youth reached age and gender-adjusted criteria for healthy fitness, and approximately 93 percent of boys and 94 percent of girls scored below the 10th percentile for maximal oxygen consumption during exercise testing. Similarly, only 18 percent of boys and 22 percent of girls reported performing the recommended 60 minutes or more of moderate to vigorous physical activity per day.
"It's important to encourage all youth to accumulate sufficient amounts of physical activity and increase their fitness levels, but this message is critical for youth with diabetes," said Gabriel Q. Shaibi, Ph.D., lead author. "Otherwise, with continuing weight gain and inactivity, they may be looking at the development of complications, such as heart disease later in life."
Another study from the same research team examined increased physical fitness and dietary modification for their roles in the management in diabetes in adolescents. This study paid particular attention to associations between lifestyle factors and overall metabolic health.
More than 100 adolescents were studied for type (both type 1 and 2) and duration of diabetes, BMI, physical fitness, and carbohydrate and saturated fat intake. Their results indicated that higher fitness levels, rather than fat, were a stronger predictor of better metabolic control. Duration of diabetes and saturated fat consumption were significant determinants of higher total and LDL cholesterol. Those with type 2 exhibited elevated levels of triglycerides similar to what is observed in the adult population.