The Prevalence of Overfat Adults and Children in the US

The overfat condition is defined as excess body fat sufficient to impair health. The problem exists in most overweight and obese individuals and can also occur in those who are normal-weight and non-obese, often due to excess abdominal fat. Despite previous indications that the prevalence overweight and obesity is leveling, these conditions are currently at their highest levels in US history. Our review estimated the number of overfat Americans at 91% for adults and 69% for children. The primary purpose of this review was to build upon previous estimations of overfat prevalence in developed countries by using new data from the Centers for Disease Control and Prevention to estimate the overfat prevalence in American adults (≥20 years) and children (2–19 years), and to expand the definition of overfat as excess body fat associated with at least one additional risk factor of impaired cardiometabolic or physical health. The secondary goals are to highlight the role of dietary sugar as a primary cause of the overfat pandemic and mention new data showing the increased prevalence of exercise that parallels the rising prevalence of overfat to further emphasize the secondary role exercise may play in fat loss. Current public health guidelines to address the overfat pandemic may require more emphasis on reducing the consumption of refined carbohydrates, including added sugars.

the Centers for Disease Control and Prevention (CDC) for 2014 show that over 70% of American adults are overweight or obese (4,5). Determination of these overweight and obese classifications are usually based on measures of body mass index (BMI), with overweight defined with a score of ≥25 to <30 kg/m 2 and obesity as ≥30 kg/m 2 . However, while BMI can overestimate fat mass in certain populations, including Polynesians, African American, and elite strength athletes, because BMI is not a direct measure of body fat it can misclassify up to 50% or more patients with both increased body fat and its associated disease risk factors (6,7).
Estimations of overfat adults and children are important for public health reasons. Excess body fat is associated with poor health, and the development of insulin resistance and low-grade systemic chronic inflammation (8,9). These conditions can lead to various cardiovascular and metabolic (cardiometabolic) impairments such as dyslipidemia, increased blood glucose, and hypertension, raising the risks of chronic diseases such as Type 2 diabetes (10,11), cardiovascular diseases (12,13), and most cancers (14). Chronic inflammation has also been linked to neurodegenerative diseases, including the most common cause of dementia, Alzheimer's disease (15,16).
The burden of excessive body fat can begin at an early age (17, 18), even in gestation (19), with over 55% of obese children estimated to have nonalcoholic fatty liver disease (20). Children with excess body fat are likely to feed the overfat pandemic and are at increased risk of becoming overfat adults with chronic disease (21-25).
The primary purpose of this review was to build upon previous estimations of overfat prevalence in developed countries by using new data from the CDC to estimate the overfat prevalence in American adults (≥20 years) and children (2-19 years), and to expand the definition of overfat as excess body fat associated with at least one additional risk factor of impaired cardiometabolic or physical health. The secondary goals were to highlight the role of dietary sugar as a potential primary cause of the overfat pandemic and mention new data showing the increased prevalence of exercise that parallels the rising prevalence of overfat to further emphasize the secondary role exercise may play in fat loss.

QUantiFyinG oVerFat
While overfat was recently defined as excess body fat that impairs health (1), in this article, we offer an expanded, quantitative description in relation to its associated cardiometabolic, physical performance, and other measurable health impairments. Overfat is both an excess amount of body fat, depicted by increased body fat percentage or waist circumference (WC), and cardiovascular, metabolic, or physical impairments caused by being overfat (26). These topics are detailed in this section and throughout this review.
Excess body fat contributes to cardiometabolic impairments, resulting in various downstream conditions such as chronic inflammation and insulin resistance, risk factors such as abnormal blood glucose, cholesterol, triglycerides, and blood pressure, and chronic diseases, including Type 2 diabetes, cardiovascular disease, cancer, and Alzheimer's disease (1). Increased body fat mass also raises the risk of mortality (27-29) and shares direct links to gallbladder disease, gout, pulmonary diseases, and sleep apnea (30), while the absence of excess body fatness lowers the risk of most cancers (14).
Physical performance impairments associated with excess adiposity include musculoskeletal disorders, such as lower-back and other pain syndromes, reduced work productivity in forms such as absenteeism and disability, as well as lower quality of life (31), and include locomotive disorders such as knee and hip osteoarthritis, lumbar spondylosis, and osteoporosis (32). Performance was also assessed in normal-weight obese children aged 3-6 years, who showed significantly worse levels of fundamental motor skills compared to their normal-weight non-obese counterparts (33). As fundamental motor skills in early life play a crucial role in physical, cognitive, and social development (34), childhood adiposity may indirectly exacerbate physical performance impairments into adulthood.
As BMI often misclassifies body fatness, reductions of misclassification rates can be improved using dual energy X-ray absorptiometry (DXA) to directly measure body fat percentage (35). DXA is one of the most accurate and precise methods of assessing adiposity (36). While there is no consensus on how to define excess body fat percentage (37), Lohman's criteria of suggested cutoffs >17.6% for males and >31.6% for females is widely accepted in body composition research (38-41). However, measurable health impairments associated with ≥2 cardiometabolic abnormalities were found at DXA-derived body fat levels >15.3% in men and >29.8% in women (42). DXA-derived body fat levels from the 1999 to 2004 National Health and Nutrition Examination Survey (NHANES) using Lohman's criteria is shown in Figure 1, which shows mean body fat for men was 28%, with the cutoff of 17.6% representing approximately the 5th percentile (17.4%), and in women, mean body fat was 39.9%, with 31.6% between the 10th and 15th percentile (43).
The overfat condition can also be evaluated indirectly using waist measures, which, like BMI, do not directly estimate body fat percentage. Epidemiologic studies have demonstrated that increased abdominal fat, assessed through WC and waist-toheight ratio (WHtR), can predict adiposity-related risk (37). WHtR was more strongly related to cardiometabolic risk factors than BMI (29, 44). In normal-weight non-obese children with a commonly used cutoff of WHtR ≥ 0.5, over 55% had one to three cardiometabolic health risk factors associated with increases in WC, triglycerides, and blood pressure (45). Adults from the NHANES, 1999-2000 cohort showed that 86% of adults with abdominal obesity [defined as WC in men ≥ 102 cm (40″), in women ≥88 cm (35″)] had at least one other cardiometabolic risk factor (46).
Based on these observations, we summarize the definition of overfat as excess adiposity measured accurately (directly, such as by DXA, or indirectly, such as by WHtR) combined with at least one additional measurable risk factor of impaired cardiometabolic or physical health.

sUBCateGories oF oVerFat
We have previously described overfat as a condition of excess body fat with two subcategories that include: (1) those who are overweight and/or obese with excess body fat and (2) normalweight and non-obese individuals with excess body fat, including those with abdominal obesity and sarcopenic obesity (1,2). Collectively, both subcategories are prevalent in adults and children, with the exception of the sarcopenic obesity condition, which is prevalent only in adults. The prevalence of the population who are overweight and obese has been well described in the literature and represents the largest subcategory of the overfat condition in the US and worldwide (1, 2).

overweight and obesity
Increases in the prevalence of various subcategories of overfat have been shown to have temporary, separate periods of levelingoff at different points over the past three decades (47)(48)(49).

normal-Weight non-obese
Since the early observations of Ruderman et al. (50), the list of associated disorders clustered into the normal-weight non-obese overfat populations has grown to include insulin resistance and chronic inflammation, dyslipidemia, elevated fasting glucose, and hypertension, and a variety of chronic illnesses that include cardiovascular diseases, Type 2 diabetes, Alzheimer's disease, and cancer (1,2). These individuals are sometimes referred to as metabolically obese normal weight, or as normal weight obese (37, [51][52][53]. It has been estimated that 20% of normal-weight non-obese adults may be metabolically obese normal weight (54), with 24% of normal-weight US adults (BMI < 25) considered metabolically abnormal with an elevated risk of chronic diseases typically associated with elevated BMI (55) and up to 40% at risk of developing metabolic syndrome (56).
In children, studies that measured body fat percentage and the WHtR may each represent reasonable methods of estimating the population of normal-weight non-obese with excess body fat, including those with BMI < 25 and those with abdominal obesity (45,58).
Two overfat conditions found in normal-weight non-obese individuals include abdominal obesity and sarcopenic obesity.

Abdominal Obesity
Excess body fat in the abdominal area includes both visceral adipose tissue and, separately, subcutaneous adipose tissue. Excess visceral fat is associated with more adverse risk factor profiles than subcutaneous fat, including its association with insulin resistance, dyslipidemia, and atherosclerosis (59)(60)(61). The excess accumulation of visceral fat is increasing among overweight and obese, as well as normal-weight non-obese individuals (48). The potential health risks of abdominal obesity are more pronounced than those due to excess body fat in other regions of the body (62). The recent rise in the prevalence of abdominal obesity in the US, which includes increases in WC, is found in both adults and children (45,49). Because the problem can occur in non-obese individuals, this condition has been referred to as abdominal overfat (2).

Sarcopenic Obesity
Defined as a progressive loss of Type 2 fast-twitch muscle fibers and strength with aging, sarcopenic obesity has a prevalence of up to 50% in those >80 years (63). Sarcopenia can coincide with an accumulation of fat within existing muscle, with the combination of higher body fat and sarcopenia being termed sarcopenic obesity (64,65). This condition occurs in those who are usually not obese and may be more appropriately called sarcopenic overfat (2).

oVerFat adULts and CHiLdren
To estimate the prevalence of overfat adults and children in the US, we combined the populations of overweight, obese, and normal-weight individuals with increased health risks (MONW). In adults, recent crude data estimated overweight and obese prevalence in the US at 70.7% (5). Metabolically obese normal weight prevalence has been estimated between 5 and 45%, with variations due to ethnicity, sample size effects, differences in MONW definition, social and demographic factors, and others (66,67). The relatively recent prevalence of MONW adult populations in North America and Europe that included both genders and a wide range of ages have been estimated by various authors to be between 24 and 36% (55,(68)(69)(70)(71)(72). However, we feel the metaanalysis by Wang et al., which showed the overall prevalence of MONW adults in the general population worldwide at 20% (95% CI 16.54-23.94), was an appropriate estimate for the US population, and was previously used for estimating overfat prevalence in developed countries (2) In children, as in adults, a wide range of normal weight high body fat conditions has been found in various populations. Mokha et al. (58) showed that in normal-weight non-obese children with a WHtR ≥ 0.5, over 55% had one to three cardiometabolic health risk factors associated with increases in WC, triglycerides, and blood pressure. In a Caucasian population of high school students, Olafsdottir et al. found 42% were normal-weight obese, defined as normal BMI with DXA body fat >17.6% in males and >31.6% in females, and with one or more risk factors for metabolic syndrome (39). Griffiths et al. (73) showed that 17.6% of normal-weight non-obese boys and 17.3% of normal-weight non-obese girls who exceeded a WHtR of 0.5 were considered "at risk, " as compared with children who were overweight or obese and above the 85th percentile, and  (2). Combined with recent rates of US overweight and obese children aged 2-19 years of 46.9% (5), we estimated the overfat prevalence of US children to be 68.9%. Figure 3 shows the prevalence of overfat adults and children in the US, with State-by-State rates of overfat, which follow overweight and obese levels, shown in Figure 4.

HeaLtH eFFeCts oF eXCess Body Fat
While the health consequences of being overweight or obese are widely known, it is the specific condition of excess body fat that is associated with various disease risk factors, chronic illness, increased morbidity and mortality, and reduced quality of life. The problems associated with the rise in prevalence of overweight and obese classifications alone have replaced the longstanding problems of undernutrition and infectious diseases (30). Moreover, the overfat pandemic, with its potential downstream conditions, has created a major global economic burden (2). In a single year (2014) in the US, for example, total health-care costs climbed to $3.2 trillion US dollars (75). Overfat-related cardiometablic and physical impairments could be a substantial portion of these annual costs.

Body Fat Measures
Various research methods have been used to quantify body fat levels in humans, including bioelectrical impedance and hydrostatic plethysmography, with DXA being one of the most accurate and precise methods currently accessible (36). Epidemiologic studies have also demonstrated that abdominal fat distribution, assessed through WC, waist-to-hip ratio and WHtR measurements, can be useful in the clinical assessment of adiposity-related risk (37), although, like BMI, these measures do not accurately estimate body fat percentage. Of these, the WHtR may be the most convenient, inexpensive, and valuable clinical indicator of health and overfat risk for use in all ethnic groups of adults and children (76,77). A simple recommendation is that the WC measurement should be less than half of a person's height (2).
While recognition of the staggering prevalence of the overfat pandemic is a key step in addressing this public health problem, it is difficult to discuss the issue without at least briefly addressing its possible causes.

LiFestyLe inFLUenCe on Body Fat
In addition to genetic influences, two lifestyle factors, physical activity, and dietary sugar, can play key roles in the development of excess body fat and are reviewed here.  More than half of US adults meet the federal 2008 Physical Activity Guidelines for Americans and regularly exercise using either aerobic or muscle-strengthening exercise, with an increase shown rising from 44% in 1998 to almost 52% in 2014 (5). Those meeting these guidelines for both aerobic activity and musclestrengthening exercise also increased from about 14% in 1998 to 21% in 2014. However, as shown in Figure 5, the recorded rates for adults being either overweight or obese rose to over 70.7% during a similar period, reflecting the overfat prevalence increase from 75 to over 90% (Figure 3). Whether these exercise recommendations are adequate or accurate is not known. However, physical activity and exercise is expected to increase energy expenditure and whole body fat oxidation, with a sedentary lifestyle decreasing insulin sensitivity and fat oxidation, potentially increasing stored body fat (78)(79)(80)(81)(82). This includes elite athletes and those in active military, who can also have excess body fat (83)(84)(85)(86). In healthy adults, high glycemic foods can also reduce overall energy expenditure by nearly 50% compared with isoenergetic meals containing whole foods (87).
While some authors have placed a strong emphasis on the importance of physical activity for reducing excess body fat (88), others feel that physical activity plays a lesser role in the development of the overfat pandemic (89). Indeed, Luke and Cooper (90) argue that despite dramatic increases in obesity rates over the past 30 years, physical activity levels in the Western population have not reduced and changed little. Swinburn et al. (91) showed that increased energy intake appears to be more than sufficient to explain weight gain in the US population, contending that the simultaneous increase in most country's obesity rates appear driven mainly by a shift toward more processed, affordable, and effectively marketed food than ever before. Finally, Basu et al. (92) showed that differences in sugar availability could explain variations in diabetes prevalence at a population level that is not explained by physical activity or being overfat. Clearly, these opposing trends, that is, the rise in the rates of overfat despite increases in physical activity are at odds with the belief that an increase in physical activity (energy expenditure) is the solution to the overfat pandemic.

dietary sugar
The largest contributing lifestyle factor to overfat would appear to be excess sugar consumption. Indeed, excess sugar in foods plays a major role in the cause of the rising rates of overweight and obesity classifications, including the monosaccharides, glucose and fructose, and the disaccharides maltose and sucrose (93). As sugar-sweetened beverages are the single largest source of added sugar and the top source of energy intake in the US diet (94), their increased consumption among adults and children may be a primary contributor to the overfat pandemic (95)(96)(97)(98). The consumption of sugar-sweetened beverages is also strongly associated with chronic illness (99).
The recommendations from the Institute of Medicine, the American Heart Association, the Obesity Society, and many other organizations is to reduce consumption of soft-drinks for children and adults (100), with the US Dietary Guidelines Advisory Committee recommending that added sugars constitute <10% of total calories per day (101). However, these recommendations have not yet been effectively implemented.
In addition to sugar-sweetened beverages, high glycemic diets, those containing foods with added sugar and other refined carbohydrates, can contribute to insulin resistance and chronic inflammation, and to the development of Type 2 diabetes, dyslipidemia, nonalcoholic liver disease, cardiovascular disease, and other chronic illness in adults and children (18, [102][103][104]. Average daily consumption of added sugar for men (335 calories) and women (230 calories) exceed recommendations of the American Heart Association of 150 and 100 calories, respectively (105). This is particularly true of refined sugar and other refined carbohydrate consumption beginning very early in life, which occurs despite current evidence suggesting that children also limit added sugar intake to <10% of total energy (106).
It is well established that early life exposure to excess sugars (other than lactose) could influence taste preferences, satiety, and health (107). In animal studies, maternal exposure to sugar during pregnancy and lactation have shown long-lasting overfat promoting effects in their offspring (108). Walker and Goran (109) found that 74% of 100 selected test samples of infant formulas, baby and children' s cereals, and other retail food items analyzed in a laboratory contained ≥20% of total calories per serving, mostly from added sugars. Of 20 yogurt products tested, the mean percent of sugar from added sugar was 63% (37% on average was naturally occurring). The popularity of packaged foods represents one problem of hidden sugars, as nutrition databases and, therefore, nutrition labels may not accurately reflect true sugar content. A number of baby food products tested by Walker and Goran (109) indicated no added sugar in their ingredients, when in actuality they contained high sugar content.
The effects of excess dietary sugar can influence cardiometabolic health rapidly. For example, reducing consumption of added sugars in the diet, without reducing calories or losing body mass, reversed a cluster of chronic metabolic diseases in children, including high cholesterol, hypertension, and nonalcoholic liver disease, within only 9 days (110,111).
While physical activity has many known health benefits and should continue to be recommended, as depicted in Figure 6, the above arguments suggest that current public health guidelines addressing the overfat pandemic require far more emphasis on reducing the consumption of refined carbohydrates, including added sugars.
An important focus of this review was to emphasize the extensiveness of the overfat pandemic as a primary public health problem deserving of more clinical attention, not unlike The National Cholesterol Education Program's Adult Treatment Panel III report that states obesity be the primary target of intervention for metabolic syndrome (26). Indeed, the prevalence of overfat is much greater, and the need for further research and consensus to build on the overfat definition presented here is obvious.

ConCLUsion
The number of overfat Americans continues to rise, with estimations of 91% in adults and 69% in children, the highest levels in US history. Recognition of the overfat pandemic is a key step in initiating its reversal and prevention. Because overfat prevalence continued rising during periods of increased exercise rates, current public health guidelines to address the overfat pandemic may require more emphasis on food, especially in reducing consumption of excess refined carbohydrates, including added sugars.
aUtHor ContriBUtions PM-originator of ideas, data collection, analysis, critical thinking, and writing of the manuscript. PL-contributed to ideas, critical thinking, and writing of the manuscript.