People who live in walkable neighborhoods with access to parks and other outdoor activities are more active and less likely to have diabetes or obesity, according to a new paper published in the Endocrine Society’s journal, Endocrine Reviews.

Nearly half of the adults in the United States have obesity, and over 11 percent of the U.S. population has diabetes. Researchers and policymakers have been searching for an effective way to promote healthy lifestyles at a population level to address these dual epidemics.

The built environment is the manmade structures that provide people with living, working and recreational spaces. This environment includes buildings, neighborhoods, parks, bike paths, restaurants, shops, roads and public transportation. Human health is affected by the physical environments we construct.

“The built environment can influence physical activity levels by promoting active forms of transportation, such as walking and cycling over passive ones, such as car use,” said Gillian L. Booth, M.D., M.Sc., of the University of Toronto, St. Michael’s Hospital of Unity Health Toronto and ICES in Ontario, Canada. “Shifting the transportation choices of local residents may mean that more members of the population can participate in physical activity during their daily routine without structured exercise programs.”

The researchers reviewed several studies on the built environment and their effects on public health and found walkable, activity-friendly cities and neighborhoods were associated with a lower risk of obesity and diabetes. One large population-based study of 32,767 people found the prevalence of obesity among adults living in highly walkable neighborhoods compared to those living in low walkability areas was 43% vs. 53%.

A study of 1.1 million adults with normal blood sugar levels found the incidence of pre-diabetes was 20% higher among people living in less walkable areas after 8 years of follow up. Another study of 1.6 million adults found a 30% to 50% higher likelihood of developing diabetes among people living in low versus highly walkable areas. In a population-based Canadian study, moving from an unwalkable to a highly walkable neighborhood was associated with a 54% lower likelihood of being diagnosed with high blood pressure.

The paper also noted that air pollution and high concentrations of fast-food restaurants are risk factors for diabetes and can substantially reduce the benefits of living in a walkable neighborhood.

“We need policies that promote healthier eating habits and opportunities to engage in active forms of transportation,” said Booth. “Designing neighborhoods that have safe and effective public transit options, cycling infrastructure and walking paths may reduce traffic related pollution.”

Staining showing mitochondria within individual muscle fibres. CREDIT Monash University

Monash University, Australia scientists have discovered an enzyme that is key to why exercise improves our health. Importantly this discovery has opened up the possibility of drugs to promote this enzyme’s activity, protecting against the consequences of ageing on metabolic health, including type 2 diabetes.

The proportion of people worldwide over 60 years old will double in the next three decades and by 2031, more than six million Australians will be over 65 years old. The incidence of type 2 diabetes increases with age so this ageing population will also result in an increased incidence of the disease globally.

One of the main reasons for the increased prevalence of type 2 diabetes with age is the development of insulin resistance, or an inability for the body to respond to insulin, and this is often caused by reduced physical activity as we age.

However, the precise mechanisms by which physical inactivity facilitates the development of insulin resistance has remained a mystery. 

Now researchers from Monash University in Australia have discovered how physical activity actually enhances insulin responsiveness and in turn promotes metabolic health. Importantly, the enzymes they have discovered that are key to this mechanism have the potential to be targeted by drugs to protect against consequences of ageing such as muscle wasting and diabetes.

The team of scientists at the Monash University Biomedicine Discovery Institute (BDI), led by Professor Tony Tiganis, reveals that reductions in skeletal muscle reactive oxygen species (ROS) generation during ageing is instrumental in the development of insulin resistance. According to Professor Tiganis, skeletal muscle constantly produces ROS and this is increased during exercise. 

“Exercise-induced ROS drives adaptive responses that are integral to the health-promoting effects of exercise,” he said. 

In a paper published today (15 December) in the journal, Science Advances, the research team show how an enzyme called NOX-4 is essential for exercise-induced ROS and the adaptive responses that drive metabolic health.

In mice the researchers found that NOX4 is increased in skeletal muscle after exercise and that this then leads to increased ROS which elicits adaptive responses that protect mice from the development of insulin resistance, which otherwise occurs with ageing or diet induced-obesity. 

Importantly, the scientists have shown that the levels of NOX4 in skeletal muscle are directly related to age-associated decline in insulin sensitivity.  “In this study we have shown, in animal models, that skeletal muscle NOX 4 abundance is decreased with ageing and that this leads to a reduction in insulin sensitivity,” Professor Tiganis said.

“Triggering the activation of the adaptive mechanisms orchestrated by NOX4  with drugs, might ameliorate key aspects of ageing, including the development of insulin resistance and type 2 diabetes,” he said. 

“One of these compounds is found naturally, for instance, in cruciferous vegetables, such as broccoli or cauliflower, though the amount needed for anti-ageing effects might be more than many would be willing to consume.”