In this two-part article (view Part 1 here), I address the importance of aerobic fitness in the general population. While Part 1 covered the importance of aerobic exercise in the general population, here I am addressing aerobic exercise specifically in people with type 2 diabetes.
Aerobic fitness and cardiovascular death in people with type 2 diabetes
The association between low aerobic fitness and increased risk of death is important to understand in people with type 2 diabetes, as they have a significantly higher risk of death from cardiovascular disease, and often have low fitness levels. Two studies have demonstrated a clear relationship between aerobic fitness and death in patients with type 2 diabetes. In a study of 1,263 men with type 2 diabetes, men in the low fitness group had approximately a two-fold increase in the risk of death from any causes over a 12-year period, compared with fit men.
To study whether physical fitness could reduce the risk of death caused by obesity in people with type 2 diabetes, one study enrolled 2,690 men with type 2 diabetes from Veterans Administration hospitals (hospitals that are operated by the Veterans Health Administration in the United States).
Participants were classified by their body mass index (BMI, which is calculated as weight in kilograms, divided by height in meters, squared):
- normal weight (BMI <25 kg/m2)
- overweight (BMI 25 to <30 kg/m2)
- obese (BMI ≥30 kg/m2)
Participants in each group were also classified by their level of aerobic fitness, which was expressed in METs. Highly fit participants achieved more than 8 METs, moderately fit participants achieved 5.1 to 8 METs, and lower fit participants achieved fewer than 5 METs.
Death from all causes was examined during an average follow-up period of 7 years, and cause of death was confirmed through Veteran’s Administration records. During the follow-up period, 172 deaths occurred in the normal weight group, 334 in the overweight group, and 256 in the obese group. When the risk of death was compared with fitness level, the researchers identified a noticeable association between the two. Specifically, each 1-MET increase in exercise capacity resulted in a 14% reduction in risk of death. This relationship was consistent across all three weight categories.
In an 8-year study of 21,925 men, unfit (low fitness), normal weight men had double the risk of death from all causes compared with fit, normal weight men. Unfit, normal weight men also had double the risk of death from all causes compared with fit, obese men. The rate of death from all causes of fit, obese men was not significantly different from that of fit, normal weight men. The study concluded that the health benefits of normal weight are limited to fit men, and that being fit may reduce the hazards of obesity.
Survival of the fittest
An editorial published in the New England Journal of Medicine in 2002 commented:
“In 1859, Charles Darwin published his theory of evolution as an incessant struggle among individuals with different degrees of fitness within a species. At that time, his explanations created remarkable controversy, but they were to revolutionize the course of science. Darwin’s writings reflected conclusions drawn from years of study and observation. Now, over 150 years later, in the era of evidence-based medicine and rigorous scientific method, when fitness is measured and study subjects are followed for years, the data supporting the concept of survival of the fittest are strong and compelling.”
Clearly, incorporating aerobic fitness into your activities of daily living has been proven beyond any doubt to be good for your overall health and your longevity. To find out more about physical activity, click here.