Environmental Factors and Obesity

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Obesity is a disorder that is becoming increasingly prevalent worldwide. Growing evidence suggests that obesity is not limited just to developed countries. Weight gain has been attributed to significant health and social difficulties. It is known to increase morbidity and mortality in non-communicable and communicable diseases. The pathophysiology of obesity is widely influenced by genetic, environmental, behavioral, and developmental factors. This article describes the global epidemiology and environmental factors affecting obesity in adults and reviews its impact on patients with this condition. It highlights the role of the interprofessional team in improving care for patients with obesity.


  • Outline the epidemiological factors leading to obesity.
  • Summarize the environmental factors associated with obesity.
  • Describe the health conditions/risks associated with obesity.
  • Identify potential areas in which healthcare providers can improve patient care and further research.


Obesity is a chronic metabolic disease caused by increased body fat stores. In clinical practice, it is defined as a body mass index (BMI) of 30 kg/m^2 or higher. Pediatric obesity is defined as a body mass index (BMI) equal to or greater than the 95th percentile for age and sex. Per the World Health Organization, worldwide obesity has tripled in the last 50 years. In 2016, more than 650 million adults aged 18 years and older were obese. It is estimated that by 2030, approximately 20% of the world population will be obese, and 38% will be overweight.[1]

The definition of obesity and its classification has been changing internationally. European guidelines are now putting more emphasis on waist circumference and BMI. Per the U.S. Preventive Services Task Force (USPSTF), increased BMI is classified as a BMI of 25 to 29.9 being overweight, 30 to 34.9 is class 1 obesity, 35 to 39.9 is class 2 obesity, and greater than 40 is class 3.[2] In Europe, a waist circumference of greater than 94 cm in men and 80 cm in women is linked to increased visceral adipose tissue and exacerbated cardiovascular risk. 

This condition is often associated with an elevated risk of chronic medical conditions such as type 2 diabetes mellitus, cardiovascular disease, stroke, hypertension, obstructive sleep apnea, and even some cancers. Obesity affects almost every organ system in the human body. It can be either a consequence of metabolic effects of adipose tissue or sometimes increased body mass itself.

Researchers have a clear understanding of disease mechanisms for most endocrine disorders, but this is not the case with obesity. It is believed that the fundamental cause of obesity is a disproportion between calories consumed and expended. However, changes in physical activity and dietary patterns are often related to environmental and societal changes.


Obesity is a complex, preventable disease that has a multifactorial process. Obesity is fundamentally associated with an excess calorie intake compared to expenditure at the individual level. At a population level, obesity is better understood by its interactions with the environment. 

Social and Economic Factors

The effect of globalization and economic changes over the past decade has generated a decreased cost and growing prevalence of fast food as well as a decrease in physical activity. On the other hand, food accessibility is also a major factor. Especially in the United States, access to affordable healthy food varies by ethnic, racial, and socioeconomic status. In minority predominant and lower-income neighborhoods, there are approximately 30% fewer supermarkets.[3]

In developing countries, there is a relationship between higher socioeconomic status and a higher likelihood of having obesity. However, there is an inverse relationship between socioeconomic status and BMI in developed countries. It is possible that in developing countries, the ability to afford food, cultural values, and less physical labor favors a larger body size, whereas developed nations can afford more nutritious food and favor high-energy exercise.[4]

Community resources and neighborhood characteristics have also been shown to play a role. In Nigeria, a study revealed that even controlled for socioeconomic status, specific factors such as poor neighborhood aesthetics, safety in the area, and distance to commercial facilities were associated with higher weights. Similar findings were seen in Missouri in the United States as well.[5][6]

Racial and ethnic variations of prevalence also exist. Non-Hispanic black and Hispanic women have a larger rate of obesity than non-Hispanic white women. This trend is seen similarly in men, although there is not a large difference between races. Asians have lower obesity rates than others. However, they have a higher body fat percentage.[7]

Lifestyle Factors

Factors such as sedentary lifestyles and amount of physical activity, restful sleep time, and stress are all independently associated with weight gain. The US Department of Health and Human Services recommends at least 150 to 250 minutes of moderate exercise per week to prevent weight gain. Physical inactivity in children and extended screen time leading to more inactive lifestyles have become more prominent. Early childhood preventative interventions such as encouragement of athletics and outdoor recreation have been shown to have long-term health benefits.[8]

Sleep was also found to be a factor. Less than six or greater than eight hours of sleep is associated with weight gain. This has also been studied greatly in children, demonstrating that even less than 1 hour of sleep per night from normal can lead to worsening obesity.[9]

Homelife factors and family influences also indirectly affect a patient's eating habits and preferences from a young age. 

Studies show that abrupt smoking cessation contributes to weight gain. Many patients may recognize this. However, the risks highly outweigh the benefits, and patients should be counseled to continue abstaining from smoking while working to maintain weight. The use of nicotine patches to help with quitting smoking reduces weight gain.[10]

Dietary Factors

The energy balance pathway is the established pathophysiology of obesity. The energy value of food is often measured in calories. The average active female needs about 2000 calories, and a male needs 2500 calories a day to maintain a healthy weight. Excess energy intake is often due to the consumption of energy-rich diets such as high- fat and carbohydrates and low intake of fiber, fruits, and vegetables. Population-based studies unveil that a high intake of sugar-heavy beverages (e.g., sweet tea, soft drinks) and irregular eating patterns lead to obesity. Drinking alcohol heavily, above the recommended limit, eating outside often, and eating processed foods are higher risks. Comfort eating, such as eating when sad or depressed, may occasionally play a role.[11][12]

Genetic Factors

Although isolated genetic factors are unlikely to explain the increasing prevalence of obesity over the last few years. Certain genetic elements and the influence of environmental conditions likely enhance the risk of obesity. An example is that physical activity levels and diet composition influence obesity risk alleles such as the FTO gene (“fat mass and obesity-associated protein”). Several non-coding genes affect obesity risk by influencing brain development or function or development of adipose tissue. Further research is required to illustrate this in better detail.[13]

Gastrointestinal Factors

Various mechanisms have been studied to understand the effects of the gastrointestinal tract on the development of obesity. The intestinal microbiota can do this in many ways by causing low-grade inflammation, affecting fatty acid production, and increasing the energy production of food. Gut microbiome diversity has a protective effect against long-term weight gain.

Previous studies have shown a correlation between the amount of Bacteroides bacteria in stool samples and weight loss. These bacteria allow for improved metabolism of carbohydrates and lipids by facilitating increased digestion of indigestible carbohydrates into fatty acids. Microbiota also causes inflammatory cytokine secretion. Probiotics show a decrease in interleukins and C- reactive protein levels, which are known biomarkers of obesity. Studies have shown a significant association between antibiotic exposure and obesity due to alterations in the diversity of gut microbiota.[14][15]

Developmental Factors

Other factors include perinatal and intrauterine exposure to high-energy diets, toxins, etc. Maternal undernutrition increases obesity risk in the first trimester. Despite this, exposure to maternal obesity with or without gestational diabetes mellitus is also associated with a heightened risk of adult obesity at later stages.[16]

Issues of Concern

Excess body weight is associated with substantial increases in morbidity. Obesity is attributed to multiple clinical co-morbidities and is thought to be a modifiable risk factor. The psychological effects of obesity continue in a vicious cycle. Those with depression and binge-eating disorder have a higher rate of obesity.[17]

Patients with obesity or overweight may endure social discrimination and stigmatization. This may negatively impact their quality of life. This starts at a young age and can last through adulthood. Studies show that this has increased over the last decade by 66%. Understanding that obesity is not just due to an imbalance of calorie intake versus expenditure but also affected by environmental, genetic, and psychosocial components.[18]

Clinical Significance

The USPSTF and National Institute of Health (NIH) recommend screening all adults over the age of 18 years for obesity. The NIH recommends screening for waist circumference as well.[19]

The assessment of these patients should begin with a thorough history and physical exam. It should include a chronology of weight gain, family history of obesity, high-risk eating behavior (such as binge eating, fast food consumption, nighttime eating, sugary beverages, etc.), exercise routines, and symptoms of cardiovascular disease. Routine tests involve laboratory testing such as lipid panel, glycated hemoglobin, blood pressure testing, and routine age-appropriate cancer screening. 

As mentioned above, obesity can affect almost every physiologic system in the human body.

Common Obesity-related Health Problems

  • Cardiovascular: Hypertension, hyperlipidemia, heart failure, venous stasis, atrial fibrillation
  • Pulmonary: Obstructive sleep apnea, restrictive lung disease
  • Renal: Chronic kidney disease, nephrolithiasis, proteinuria
  • Gastrointestinal: Gastritis, gastric reflux disease, non-alcoholic steatohepatitis, cholelithiasis
  • Neurologic: Stroke, migraine, pseudotumor cerebri (idiopathic intracranial hypertension)
  • Endocrine: Diabetes Mellitus type 2, Polycystic ovarian disease (PCOS)
  • Musculoskeletal: Osteoarthritis, low back pain
  • Infectious disease: Increased susceptibility to infection
  • Cancer: Colorectal cancer, breast cancer, endometrial cancer

Interestingly, recent studies have indicated that patients who were overweight or had class 1 obesity had an overall mortality risk similar to those with a normal BMI. These results were fairly controversial and have caused scientists and healthcare providers to re-examine the definition of optimal body weight. Despite this, increased life expectancy does not necessarily equate to improved healthy life years. It is, therefore, still an issue of serious concern.[20][21]

Other Issues

Obesity contributes to a large portion of healthcare expenditure in the world. Approximately 5 to 7% of the national health expenditure in the U.S. is associated with obesity; this does not include diseases such as cardiovascular disease, cancer, etc.

Globally, obesity is a huge burden. For example, the cost of obesity in 2019 ranged from 0.8% of gross domestic product (GDP) in India and 2.4% of GDP in Saudia Arabia. Reducing obesity prevalence by even 5% is shown to have an average reduction in economic costs between 5 to 13% worldwide.[22] 

Enhancing Healthcare Team Outcomes

Clinicians have a responsibility to identify obesity as a gateway disease. Identifying appropriate prevention and treatment measures for obesity and its comorbidities is imperative. Patients and their caregivers must understand that obesity is a chronic disease, and weight management will need to be a lifelong process.

A multidisciplinary and interprofessional approach to obesity is essential to determine the barriers to weight maintenance. Involving the patients in discussions regarding environmental factors affecting obesity promotes health literacy. Psychosocial factors have strong associations with overeating. Health care workers at the primary care level, including therapists and psychologists, can potentially play a significant role in identifying these individuals, referring them to health care providers for further screening and treatment, and providing behavioral therapy targeted towards their eating habits.[23]

Studies have revealed a lower risk of obesity when there is a higher satisfaction with public transportation, safety in the neighborhood, and accessibility to sports facilities. Governmental/ charity-based improvement in these functions will likely improve weight loss.[24]

Social policy changes by increasing the availability of healthy foods, regulating portion sizes and ingredients, and further promoting physical activity are vital. Another potential change is requiring calorie counts of food to be listed in fast food and other restaurants.[25]

Nursing, Allied Health, and Interprofessional Team Interventions

Allied health workers, nurses, nurse practitioners, and advance practice providers are often the first point of contact between patients and the healthcare system. They must be aware of the environmental and genetic factors that affect obesity to tailor their care towards that. Understanding the clinical correlations between obesity and chronic medical conditions is also necessary. 

Dieticians and nutritionists can also play a significant role by educating patients on proper eating habits, improving food choices, and pointing out foods to avoid.

Healthcare workers in the obstetrics and the family practice field should incorporate guidelines to integrate optimal pregnancy nutrition and weight gain, management of gestational diabetes mellitus, and feeding strategies. The USPSTF recommends that health care providers refer adults with a BMI of 30 or higher to intensive, multicomponent behavioral intervention.[26] Behavioral interventions include encouraging self-monitoring of weight, and written and visual tools should be provided to support weight loss.

Nursing, Allied Health, and Interprofessional Team Monitoring

Weight loss maintenance is of utmost importance. Monitoring patients closely for adherence to weight loss regimens can be done more efficiently with nursing, allied health, and interprofessional team monitoring. It is seen that combined pharmacotherapy and behavioral intervention provide greater weight loss maintenance and initial weight loss in 12 to 18 months. 

Patients should be followed up often, at least in the first 12 to 18 months. Frequent physical exams and laboratory testing should be pursued to screen for comorbidities. Further research is required on at-risk subpopulations such as racial/ethnic groups, older adults, etc. More information is needed regarding patient-centered outcomes of current weight loss regimens. Emphasis should be placed on psychosocial factors and quality of life.



5/1/2023 5:45:54 PM



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