What Is Obesity?
Obesity is a chronic disease that is currently defined as a body mass index (BMI) greater than 30.1 BMI is a system used to estimate body fat and compare weights independent of stature across a population. It is calculated by dividing body weight (kg) by the square of height (m2).
What Is the Prevalence of Obesity?
According to the 2021 National Health and Nutrition Examination Survey, the prevalence of obesity among adults (age >20 years) in the U.S. was 41.9% between 2017-2020, increasing from a prevalence of 30.5% between 1999-2000.2 Prevalence in children and adolescents (age 2-19 years) was 19.7%.
What Causes Obesity?
1) Lifestyle Causes – Lifestyle, behavioral, and environmental factors are key causes of obesity.3 Excess dietary consumption relative to energy expenditure is most commonly the direct cause. The promotion of processed and high caloric foods and the decrease in physical activity in the recent decades contribute to the obesity epidemic. Decreased quality or quantity of sleep (sometime caused by medical conditions such as obstructive sleep apnea) can also contribute to weight gain by promoting hormonal, metabolic, and behavioral disturbances.4
2) Genetic & Medical Causes – Underlying genetic factors, neuroendocrine causes, and other medical conditions such as Hypothyroidism, Cushing syndrome, polycystic ovarian syndrome, and male hypogonadism can also lead to weight gain.4 A small percentage of obesity is attributed to monogenetic disorders such as Prader-Willi syndrome, Bardet-Biedl syndrome, and Leptin receptor deficiency. A relatively sudden weight gain may suggest an underlying neuroendocrine condition.
3) Psychosocial Causes – Studies have shown that mental health and social networks may be linked to obesity.3,4 Mental health disorders such as depression, anxiety, and binge-eating disorders are known to be associated with obesity. Stress can also increase appetite and cause individuals to seek comfort food, and the stigma associated with weight can lead to further stress and overeating, exacerbating weight gain.4 Research has also shown that individuals are more likely to become obese if they have close relationships with other who are obese (eg, spouses, siblings, friends).3
What Are the Health Effects of Obesity?
Globally, obesity is one of the leading causes of morbidity and mortality. 5 In 2015, 4.0 million deaths (7.2% of all-cause deaths) globally were attributed to excess weight. Obesity is known to be associated with dyslipidemia, coronary artery disease, diabetes, sleep apnea, liver disease, and certain types of cancers.6 The leading causes of BMI-related deaths were cardiovascular disease (CVD) and diabetes.
What Is the Link Between Obesity and Diabetes?
There is strong evidence suggesting that obesity is the greatest risk factor for developing prediabetes and type 2 diabetes mellitus (T2DM), with estimates that nearly 90% of T2DM can be attributed to obesity.7 Excess visceral and abdominal adiposity are associated with metabolic abnormalities linked with the development of T2DM such as insulin resistance, pancreatic b-cell dysfunction, and dyslipidemia.8,9 Studies have consistently demonstrated abdominal obesity as being a major risk factor for CVD as well.10,11
Both obesity and T2DM are associated with insulin resistance.12 Increases in intra-abdominal fat mass can disrupt the release of hormonal factors that regulate metabolism.7,12–14 It is postulated that increases in plasma free fatty acid (FFA) levels (from increased adiposity and dietary intake) encourage cellular uptake and utilization of lipids instead of glucose, leading to a persistent hyperglycemic state and insulin resistance. Additionally, abdominal adiposity is associated with greater insulin resistance than peripheral adiposity, as abdominal fat is more metabolically active and lipolytic, actively releasing FFAs into the bloodstream.
In response to insulin resistance and persistent hyperglycemia, the body increases both the function and mass of pancreatic b-cells to produce more insulin to control blood glucose levels. However, as insulin resistance exacerbates and chronic hyperglycemia, hyperlipidemia, and hyperinsulinemia persist, pancreatic b-cells undergo damage through various pathological processes.15 The resulted insulin resistance and impaired insulin secretion are key characteristics of T2DM.15,16
What Should Obese Individuals With Diabetes Do?
The current guidelines by the American Diabetes Association (ADA) recommend that adults with prediabetes or T2DM who are overweight (BMI >25 kg/m2) or obese (BMI >30 kg/m2) to achieve and maintain a >5% weight loss.17,18
1) Lifestyle Changes – The ADA emphasizes the importance of making significant lifestyle changes to achieve appropriate weight loss and glycemic control.19 Making dietary changes and engaging in physical activity to create a 500-700 kcal/day energy deficit are recommended. Modest and sustained weight loss in overweight or obese individuals with T2DM has shown to improve glycemic control, blood pressure, and lipid profile.
2) Pharmacotherapy & Surgery – Although individuals and their health care team should carefully consider the pros and cons of weight loss medications, pharmacotherapy may be effective as adjuncts to lifestyle changes in individuals with T2DM and BMI >27 kg/m2.19 Additionally, metabolic surgery (also known as bariatric surgery, a procedure that makes modifications to the stomach or intestines with the goal of facilitating weight loss) may be considered in conjunction with lifestyle changes for adults with T2DM and BMI >40 kg/m2 (BMI >37.5 kg/m2 in Asian Americans) and with BMI >35.0-39.9 kg/m2 (BMI >32.5-37.4 kg/m2 in Asian Americans) without improvements in weight or comorbidities. Individuals who undergo surgical procedure should receive long-term support and monitoring of metabolic and nutritional status.
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