Slimming down is tough.

Even if you exercise regularly and eat well, you may still get different (and possibly disappointing) results than someone who follows the same regimen.

What causes this disparity? There are many possible answers, but one of the least visible causes may be going straight into your body without you knowing it – air pollution.

Pollutantsdisrupt appetite-goverance

Fine particles, or PM2.5, and ultrafine particles, particles measuring, less than 0.1 microns in diameter,are believed to be the pollutants most responsible for disrupting metabolic function.

When you breathe in, particle pollutants irritate the alveoli in your lungs that normally allow oxygen to pass into your blood stream. Consequently, the lining of your lungs releases hormones that make insulin less effective, diverting blood from insulin-sensitive muscle tissue and stopping your body from properly regulating its blood sugar levels.

Additionally, particle pollution may cause your body to flood your blood with higher levels of inflammatory molecules called “cytokines”, which trigger immune cells to invade otherwise healthy tissue.

According to a 2014 study published in Environmental Health, this response not only interferes with your tissue’s ability to respond to insulin, but the resulting inflammation may also disrupt the hormones and brain processing that govern your appetite.¹

This can result in feeling hungry even when you’re totally full or satiated. The additional food you eat to feed your artificial appetite may result in weight gain over time. – The Berkeley researchers found,that air pollution exposure could lead to a 13.6% increase in body mass index (BMI), the most popular metric for a healthy weight.

This pollution-triggered inflammation may also lead to a host of health issues, such as:²

• obesity
• diabetes
• hypertension

Air pollution and obesity linked

A 2010 study published in Arteriosclerosis, Thrombosis, and Vascular Biology first tackled this question while looking into how living in big cities could put people at a higher risk of heart disease compared to their rural counterparts.³

In the study, some mice were given clean, filtered air to breathe while others breathed the kind of dirty air you’d find near a congested freeway. The researchers periodically weighed the mice and performed tests to analyze their metabolic function.

In just 10 weeks, the mice exposed to the polluted air displayed greater volumes of body fat, both around their midsections and around internal organs, and the fat cells were approximately 20% larger in the mice exposed to polluted air.

The fatter mice also seemed to have become less sensitive to insulin — one of the first symptoms in the development of type 2 diabetes.

Several scientific studies show that humans are susceptible to the same alarming health consequences.

Air pollution may lead tohealth problems

A particularly noteworthy study examined the medical records of 62,000 people in Ontario, Canada over a 14-year period.⁴

The researchers discovered that the risk of developing diabetes increased by roughly 11% for every 10 micrograms of fine particles in a cubic meter of air — this is a disturbing figure considering that PM2.5 pollution in some cities and regions affected by wildfires have been recorded at 500 micrograms per cubic meter of air.⁵

Wildfire smoke is rarely limited to the immediate vicinity of fire. Smoke can travel over continents and cross oceans, traveling thousands of miles from its source.

A 2015 study in PLOS One offered similar evidence of increased hypertension, insulin resistance, and waist circumference in a sample of almost 4,000 people living in a highly polluted area.⁶

In 2020, University of Colorado at Boulder researchers found that young adults in Southern California experienced a change in the composition of the gut microbiome in connection with their exposure to air pollutants.⁷ The findings, published in Environment International, determined that ozone had a greater impact on gut microbiome composition than gender, ethnicity, and diet.

Young people with greater ozone exposure experienced reduced microbial diversity within the gut. The reduction in diversity included growth in Bacteroides caecimuris; at elevated levels, this bacterial species is associated with higher levels of obesity.

Children arevulnerable

Scientists are specifically concerned that air pollution may alter the metabolism of infants and young children, making them more likely to become obese as they age.

A 2012 longitudinal study published in American Journal of Epidemiology addressed this question by examining the health of nearly 800 children growing up in the Bronx borough of New York City from 1998 to 2006.⁸

While pregnant, the children’s mothers wore a small backpack for the study that measuredair qualityduring their day. Over the next seven years, the children’s health was monitored at regular intervals.

Accounting for other factors like diet and income,children born in the most heavily polluted areas were nearly two and a halftimes likelier to be considered obese, compared to children living in neighborhoods with cleaner air quality.

Further supporting these findings, a 2017 study in Pediatric Obesity demonstrated that even in the first six months, babies of mothers living in heavily-polluted areas appear to put on weight more rapidly than those in areas with cleaner air.⁹

It’s important to be cautious about giving too much weight to these findings. The studies only establish a link between exposure and outcome, but can’t prove that one factor causes another.

But researchers continue to uncover key findings that fill those gaps.

A 2016 study published in Hypertension tested a small group of subjects in Beijing for two years.¹⁰ The researchers discovered that whenever the big city’s notorious smog blanketed the sky, telltale indicators of developing issues like insulin resistance and hypertension peaked — solidifying more concrete evidence that the air quality may be directly linked to metabolic processes that lead to obesity.

Air pollution is both global and issue

While scientific research continues to uncover the link between air pollution exposure and obesity, what can you do to protect yourself from this potential threat to your health?

The scientific community emphasizes thatindividual, short-term risk posed by poor air quality shouldn’t be understood as the basis for obesity by itself without considering other facets of your lifestyle, such as diet or physical activity.

However, given the large numbers of people living in cities plagued with pollution — up to 68% of the world’s population by 2050, according to the United Nations — the long-term risk could be massive.¹¹

When it comes to positively impacting your air quality as well as your weight, focus on the change you can make in your own world.

The global air pollution crisis is obviously impossible for a single person to crack. On a global scale, some other measures that could help improve air quality include:

• monitor your air quality, especially levels of harmful PM2.5
• restricttraffic in densely populated urban areas to reduce traffic pollution
• redesignstreets to make them friendlier to pedestrians and cyclists
• increaseinvestment in renewable energy sources

Losing weight is challenging enough without having to worry about invisible pollutants wreaking havoc on your metabolism.

You can’t take on the burden of solving the global air quality crisis alone, but you can take control of your indoor air quality and begin making positive changes in your life today.

A healthy diet and regular exercise are still the most vital keys to success in your weight-management journey, but a little clean air might help boost your overall health and wellness.