It's known that lack of exercise, poor eating habits, genetics, and lifestyle factors can all contribute to the onset of prediabetes and type 2 diabetes. I have spent many years touting the benefits of lifestyle change to prevent and manage these health conditions—and in some cases reverse them. Exercise is a particularly important lifestyle management tool because of its ability to lower inflammation (the underlying cause of insulin resistance) naturally.
But what being active by itself is not enough to overcome the negative environmental effects? Studies have been coming out for over a decade already examining the association between the onset of type 2 diabetes and persistent organic pollutants (POPs) like those found in pesticides, as well as air pollution emitted by cars and trucks. While we usually think of air pollution as mainly contributing to respiratory problems and lung diseases, there’s mounting evidence that it is also implicated in health conditions like type 2 diabetes.
A recent systematic review and meta-analysis (1) on studies conducted in Europe and North America reported a positive association between air pollution and risk of developing type 2 diabetes. In a recent study (2), air pollution was found to have contributed to 3.2 million new diabetes cases in 2016, or about 14 percent of the total, globally. In the United States, air pollution has been linked to 150,000 new cases of type 2 diabetes each year. Although less evidence has been collected in developing countries where air pollution concentrations are much higher in many of them, long-term exposure to air pollution (including both ambient particulate matter and gaseous pollutants) has been reported to be associated with an increased risk of type 2 diabetes and higher fasting blood glucose levels, especially in individuals who were younger or overweight or obese, in 33 different regions of China (3).
Fresh off another trip to China (and exposure to an excess of smoggy air) where I lectured about the importance of lifestyle management to prevent and manage diabetes, I still find it hard to assess exactly how much of the environmental impact of poor air quality that exercise can overcome. Even though exercise is anti-inflammatory in nature, particulate matter and other toxins in the air are breathed in and lead to inflammation in the body, a state underlies most metabolic diseases, including insulin resistance, obesity, type 2 diabetes, heart disease, and more. Insulin resistance is present long before the onset of type 2 diabetes and results not only from inherited and lifestyle factors but also likely from environmental conditions. Unfortunately, developing countries that are more dependent on the use of coal are at greater risk. One in two people in China already has prediabetes or type 2 diabetes (compared to one in three in the U.S.). Rates of cigarette smoking are higher in China as well, and few, if any, regulations are in place to reduce exposure to second-hand smoke in the cities and even in office settings in many Chinese cities. (The cigarette smoke was heavy in one fitness/recreational area full of treadmills that I recently walked through in a building in Nanjing, China.)
So, then, how much of the inflammatory effect of polluted air can the anti-inflammatory properties of exercise can cancel out? Although we can't control all the air that we breathe and even if healthy lifestyle habits including a better diet, more physical activity, improved gut health, and a weight loss regimen are not enough to overcome the effects of environmental pollution, it’s still likely that lifestyle improvement can drive down the risk of getting type 2 diabetes or improve your ability to manage it. Just do your best to limit your exposure to particulate matter in the air by exercising indoors on days with worse air quality (regardless of where you live), wearing a mask to limit your exposure to air pollution when outdoors, and avoiding cigarette smoke (both indoors and outdoors) as much as possible.
Eze IC1, Hemkens LG, Bucher HC, Hoffmann B, Schindler C, Künzli N, Schikowski T, Probst-Hensch NM. Association between ambient air pollution and diabetes mellitus in Europe and North America: systematic review and meta-analysis. Environ Health Perspect. 2015 May;123(5):381-9. doi: 10.1289/ehp.1307823.
Bowe B, Xie Y, Li T, Yan Y, Xian H, Al-Aly Z. The 2016 global and national burden of diabetes mellitus attributable to PM2·5 air pollution. Lancet Planet Health. 2018 Jul;2(7):e301-e312. doi: 10.1016/S2542-5196(18)30140-2.
Yang BY, Qian ZM, Li S, Chen G, et al. Ambient air pollution in relation to diabetes and glucose-homoeostasis markers in China: a cross-sectional study with findings from the 33 Communities Chinese Health Study. Lancet Planet Health. 2018 Feb;2(2):e64-e73. doi: 10.1016/S2542-5196(18)30001-9.