2
Key Points
➤ Multiple factors contribute to the development of obesity and its
consequences.
• Environment, genetics and epigenetic influences all influence the
condition.
• Environmental elements include cultural, life style, emotional
conditions, medications, toxins, infections, hormonal imbalances and
gut microbiota.
➤ In 2017–2018, the prevalence of obesity was estimated to be ~42% in
U.S. adults (≥20 years of age) and ~18.5% of youths (2–19 years of age).
➤ According to a projection analysis in 2019, ~50% of U.S. adults will have
obesity by 2030, with ~25% of adults having severe obesity (body mass
index [BMI] ≥35 kg/m
2
).
Definition
➤ "Obesity is defined as a chronic, progressive, relapsing, and treatable
multi-factorial, neurobehavioral disease, wherein an increase in body
fat promotes adipose tissue dysfunction and abnormal fat mass
physical forces, resulting in adverse metabolic, biomechanical, and
psychosocial health consequences."
Classification of Obesity
Body Mass Index (BMI)
Body mass index (BMI) in kilograms per meters squared (kg/m
2
)
a
Normal
Weight
18.5–24.9
Overweight
25.0–29.9
Class I
Obesity
30.0–34.9
Class II
Obesity
35.0–39.9
Class III
Obesity
≥40
Waist Circumference (WC)
b
Abdominal Obesity – Men
≥40 inches
≥102 centimeters
Abdominal Obesity – Women
≥35 inches
≥88 centimeters
a
Different BMI cut-off points may be more appropriate based upon gender, race, ethnicity, and
menopausal status. For example, among Asians, a BMI >23 kg/m2 may be a more appropriate cut-
off point to define overweight and to screen for type 2 diabetes mellitus. Among postmenopausal
women, BMI may underestimate percent body fat.
b
Different WC abdominal obesity cut-off points are appropriate for different races (i.e., ≥ 90
centimeters for Asian men and ≥ 80 centimeters for Asian women)
