on measured weight and height of adults from the nationally representative National Health and Nutrition Examination Survey (NHANES) indicate that the most recent estimate (2017–2018) is that 42.4% of adults in the United States have obesity [4] – far surpassing the 2020 target of 30.5% [8]. This finding represented a significant increase compared to the prevalence in 1999–2000 of 30.5%, but, notably, it was a nonsignificant increase compared to the previous cycle (2015–2016) of 39.6% [4]. The earliest national estimates of obesity prevalence in the United States, from 1959 to 1962, indicated that just 10% of men and 16% of women had obesity at that time [26]. Several studies have demonstrated that there has been an overall shift in the US population distribution for BMI toward the upper end of the BMI distribution [26–28].
There are no notable differences between men and women or according to age group in the overall prevalence of obesity [4]. However, the prevalence of severe obesity (BMI ≥40 kg/m2) is higher among women. In terms of differences by race and Hispanic origin, the prevalence of obesity in the United States is highest among non‐Hispanic black women (56.9%) and lowest among non‐Hispanic Asian women (17.2%). Generally speaking, there is greater variability in the prevalence of obesity among women than among men in the United States and globally. Among US men, there are no significant differences between non‐Hispanic Whites, non‐Hispanic Blacks, and Hispanics – although the prevalence among non‐Hispanic Asian men is significantly lower than these three other population subgroups [4]. This may relate to the fact that US analyses of Asian populations do not use Asian cut‐offs to define obesity. Therefore, the prevalence of obesity appears to be markedly lower.
State‐level obesity levels in the United States are based on the Behavior and Risk Factor Surveillance Survey (BRFSS), which uses self‐reported weight and height collected during telephone surveys to determine BMI. The response rate for BRFSS is also notably lower than that for NHANES, which may result in greater selection bias [17]. Nonetheless, the data are useful for providing insights into the geographical distribution of obesity in the United States. The most recent round of BRFSS (2018) found that no state or territory had a prevalence of obesity less than 20% (Fig. 2.1) [29]. Nine states (Alabama, Arkansas, Iowa, Kentucky, Louisiana, Mississippi, Missouri, North Dakota, and West Virginia) had a prevalence of obesity of 35% or greater [29]. In general, the South (33.6%) and the Midwest (33.1%) had the highest prevalence of obesity, consistent with earlier BRFSS surveys [29].
Childhood obesity
Today, one in five children (18.5%) in the United States have obesity, which is more than three times the prevalence observed in 1978 (5%) [30]. However, data from NHANES suggest that the overall prevalence has plateaued in recent years (after 2004) among US children aged 2–19 years [31]. The plateau is occurring at high levels of obesity, particularly among Hispanic and black children: in 2016, 26% of Hispanic, 22% of black, and 14% of white children had obesity [31]. With regards to age groups, obesity in 2‐ to 5‐year‐olds has been decreasing since 2004 (though NHANES data showed a spike from 2014 to 2016), has plateaued in 6‐ to 11‐year‐old, and continues to increase in 12‐ to 19‐year‐old (a 3 percentage point increase between 2004 and 2016) [31].
Childhood obesity is a strong predictor of adult obesity [32–35]. Some have posited that in the United States, obesity patterns are established by age 11 [31]. Once children are on a trajectory of obesity, it is difficult to change. Two‐year‐olds with severe obesity only have a 1 in 5 chance of not having obesity at age 35, and 5‐year‐olds with severe obesity only have a 1 in 10 chance of not having obesity at age 35 [35]. US adolescents (12–21 years) with obesity are 16 times more likely to develop severe obesity (BMI ≥40 kg/m2) as young adults (18–33 years) than adolescents who are overweight or have a healthy body weight [36]. Given current levels and trends in childhood obesity in the United States, more than 57% of today’s children and adolescents are predicted to have obesity at age 35 [35].
In other parts of the world, greater progress has been made in halting the rise of childhood obesity. In Switzerland, the prevalence of obesity among children aged 6–12 years has plateaued in recent years at much lower levels than the United States: 5.3% in 2017–2018 [37]. Similarly, in 2008, it was shown that the prevalence of obesity among 2‐ to 18‐year‐old in Australia had plateaued at 5–6% [38]. In fact, a handful of European countries have even reported declines in childhood obesity. In Italy, the prevalence of obesity among 8‐ to 9‐year‐old declined significantly from 12.0% in 2008 to 9.3% in 2016 [39]. Declining trends were observed across sociodemographic groups, though not statistically significant among children with low education or foreign mothers [39]. Similarly, from 2000 to 2007, the prevalence of obesity among 7‐ to 9‐year‐old children in France declined from 3.8 to 2.8% (though not statistically significant) [40].
The opposite is seen in other parts of the world, particularly rapidly developing economies, where childhood obesity is increasing. For example, in China, the prevalence of childhood obesity increased from 5.3% in 1995 to 20.5% in 2014 and showed no sign of stabilizing [41]. In Colombia, the prevalence of combined overweight and obesity among 5‐ to 9‐year‐olds increased from 14.3% in 2005 to 18.9% in 2010, and among 10‐ to 17‐year‐olds, these numbers are 13.7 to 16.7%, respectively [42]. Thus, trends in the United States, Australia, and many European countries suggest that childhood obesity can be prevented at the population level. Still, similar efforts are needed in other parts of the world where the prevalence of childhood obesity continues to increase.
Global obesity
At least six global analyses of mean population BMI and/or prevalence of overweight and obesity exist [1,2,11,43–45] – all but one [45] using measured height and weight – and have reported significant cross‐country differences. It is important to preface this section with a note that the figures provided in these global analyses are from models with different assumptions and different levels of uncertainty. Herein, we describe high‐level regional trends and point out outlier countries, but country‐specific publications should be referenced for more specific and conclusive information. The most up‐to‐date estimates show that in 2016 the global average BMI for the adult population was 24.5 kg/m2 for men and 24.8 kg/m2 for women compared to 21.7 and 22.1 kg/m2 in 1975, with a higher variability for women compared to men [2]. This means that over the past four decades, the average weight of a man with a height of 170 cm has increased by approximately 8 kg and that of a woman with a height of 160 cm by about 7 kg.
In 2016, the lowest prevalence of adult obesity was observed in the low‐income regions with the exception of the high‐income Asia Pacific region, which recorded the lowest prevalence among women (4.3%) (Table 2.3). In every region, the prevalence of obesity among women was higher, and in a few, comparable to that observed among men. The highest levels of adult obesity were observed in Central Asia, the Middle East, North Africa (35.2% for women and 22.4% for men); Oceania (30.0% for women and 20.3% for men); high‐income Western countries (29.6% for both men and women); and Latin America and the Caribbean (29.2% for women and 21.0% for men).
Figure 2.1 Prevalence of obesity (body mass index ≥30 kg/m2) among adults in the United States in 2011 and 2018 [29]. Data are from the Behavioral Risk Factor Surveillance System, a telephone interview survey conducted by the US Centers for Disease Control and Prevention with state health departments that collects self‐reported information on height and weight. *Sample size <50 or the relative standard error (dividing the standard error by the prevalence) ≥30%.
Source: Centers for Disease Control
