Normal-Weight Obesity Related Clinical Issues

Part 1 Prevalence of obesity in China:effects of various DefinitionsBody mass index(BMI)and body fat percentage(BF%)are commonly used methods to assess obesity.Although BMI is based on height and weight to assess obesity,it may not accurately evaluate the degree of fat accumulation.It is usually of high specificity and low sensitivity to diagnose obesity.Therefore,the value of BMI in assessing obesity has been challenged recently.BF%is a direct indicator of obesity and can distinguish between fat and non-fat tissue.Compared with BMI,the BF%is more accurate.This article compares three commonly obesity criteria,analyzes the characteristics of obesity epidemiology in China,and explores more accurate assessment methods to provide the evidence for clinical intervention.AimsTo explore the prevalence and epidemic characteristics of obesity in China and provide the evidence for early interventions and decrease complications of obesity.MethodsThe population-based cohort study was a part of China National Diabetes and Metabolic Disorders Survey(CNDMDS)during 2007-2008.A multi-stage stratified sampling method was used to select a nationally representative sample of Chinese adults aged?20 years.A structured questionnaire was used to collect the information and physical examination.The cut-off values which defined as being overweight and obesity were greater than or equal 24 kg/m2 and 28 kg/m~2 BMI,respectively.Abdominal obesity was considered to be more than or equal 90 cm and 85 cm waist circumference(WC)in men and women.Men and women with greater than or equal 20%and 30%BF%were considered to be obesity.Bioelectrical impedance analysis(BIA)was used to measure BF%.The t-test was used for the comparison between groups.Male BF%?20%and female BF%?30%were gold standards to analyze the optimal cut-offs of BMI and WC between men and women by Receiver Operating Characteristic(ROC)curves.Results14,204 women and 9,718 men aged 20-88 years were included in this study to assess the clinical characteristics of obesity in china.The average age of these subjects was 45.02±13.63 years.Using BMI as standard,the prevalence of overweight and obesity were 46.51%in women and less than 56.62%in men,among them there were 13.37%obesity in women,and 17.10%obesity in men,respectively.The prevalence of abdominal obesity rate were 37.73%and 29.94%in men and women,when WC was used as standard.When BF%was used as standard of obesity,the prevalence rate of men and women was respectively.77.79%and 59.16%.When the cut-off values(defined as being obesity)in men and women were greater than or equal 20%and 30%BF%,respectively,the corresponding cut-off values of BMI were 22.97 kg/m~2 and 22.91 kg/m~2.ConclusionMen had higher prevalence of overweight and obesity than women in China.It was possible to underestimate the prevalence of obesity just by BMI.Therefore,we suggest that BF%should be a part of comprehensive assessments of multiple methods to evaluate obesity.Part 2 Body fat percentage cutoffs for risk of cardiometabolic abnormalities in the Chinese adult population: a nationwide studyAlthough BMI is currently the main measurement for obesity,it may not accurately evaluate the degree of fat accumulation.Therefore,direct measurement of body fat using simple methods such as Bioelectrical impedance analysis(BIA)may be a better surrogate for the assessment of obesity.However,neither the WHO nor any major scientific society involved in the study of obesity has defined a normal value for body fat percentage(BF %).China has a large population,and in recent years,the prevalence and incidence of obesity have dramatically increased.Compared with Caucasian populations,the Chinese are relatively slim,but for the same BMI,their BF% has been found to be relatively higher.Therefore,it is necessary to establish the BF% cutoffs suitable for Chinese populations.However,the relevant literature is limited,and the reported BF% cutoffs of Chinese populations are mainly based on local areas and are thus less representative for the nationwide Chinese population.In this study,we analyzed data from the 2007–2008 China National Diabetes and Metabolic Disorders Study(CNDMS),with aim of investigating the optimal cut-offs of the BF%.AimsThe direct assessment of Body fat percentage(BF%)by using simple methods might be an alternative index of obesity.We aim to investigate the optimal cut-offs of the BF% relating to metabolic disorders and cardiovascular risks of China.MethodsThe data were obtained from CNDMDS in 2007–2008.Participants with age of 20-75 years and with a BF% measurement record were included.The BF% was measured by using a foot-to-foot bioelectrical impedance analysis.Receiver operating characteristic curve was used to decide the optimal BF% cutoffs for predicting the risks of diabetes,hypertension,metabolic syndrome(Met S),and 10-year cardiovascular events(estimated by Framingham risk score [FRS]).ResultsA total of 23,769 participants was enrolled with the mean age of 44.88 years,the male percentage is 40.59%,and the mean BF% is 25.22%.The mean BF% of subjects who had diabetes,hypertension,metabolic syndrome,and FRS ?10% were higher than those without diabetes,hypertension,metabolic syndrome,and FRS ?10%.In men,the optimal BF% cutoffs for these four endpoints were 24.50%,24.90%,24.21%,and 22.10%,respectively.In women,they were 35.69%,32.50%,32.60%,and 32.31%,respectively.Based on the weights of these endpoints,the pooled optimal BF% cutoff was 23.67% and 32.88% in men and women,respectively.ConclusionWe suggest the optimal bioelectrical impedance analysis(BIA)measured BF% cutoffs for predicting risk of cardiometabolic abnormalities to be 24% and 33% in Chinese men and women,respectively.Part 3 Prevalence and Cardiometabolic Risks of Normal Weight Obesity in Chinese Population: A Nationwide StudyThe status of normal BMI but with increased BF% is defined as normal weight obesity(NWO).A number of studies have reported increased cardiovascular risks in NWO populations,and NWO may even increase the risk of death from cardiovascular disease in the elderly.However,the prevalence of NWO differs among different populations.In our previous studies,we have calculated the cut-off value of BF in the Chinese population based on the prevalence of cardiometabolic risks.We found that the cut-off value of BF% was lower in the Chinese than in Caucasian populations.In addition,the cut-off value of BMI for diagnosing diabetes in the Chinese also differed from that of Caucasian populations.Therefore,because there is a lack of relevant research,our study described the prevalence of NWO in Chinese population,and the correlation between NWO and the risk of metabolic and cardiovascular disease based on the CNDMDS population from 2007 to 2008.AimsSeveral studies have reported increased cardiovascular risks in normal-weight obesity(NWO)populations.We aimed at investigating the prevalence of NWO and its relationship with cardiometabolic risks in Chinese patients.MethodsThe data were obtained from the CNDMDS in 2007–2008.Participants aged 20-75 years old who had the BF% measurement record were included.The BF% was measured by using the BIA.All results with P values < 0.05 were considered statistically significant.The population of the entire fourth census was used to standardize the prevalence.The BF% was measured using the biological impedance method.ResultsTotal 23,748 people(9,633 males and 14,115 females)were enrolled and the prevalence of NWO was 9.52 % for men,5.90 % for women.The prevalence risks of diabetes,Framingham risk score(FRS)?10%,hypertension,and metabolic syndrome(MS)were significantly increased in the NWO group(odds ratio [OR]1.519,95% confidence interval [CI] 1.262–1.828;OR 1.973,95% CI 1.596–2.439;OR 1.525,95% CI 1.333–1.745;OR 2.175,95% CI 1.920–2.463,respectively)compared with the normal group.To further investigate the association between NWO population and cardiometabolic risk,after excluding abdominal obesity participants,the analysis suggested NWO population with normal WC have higher risks in DM,FRS ? 10%,HTN,and Met S than normal WC but not NWO.ConclusionCardiometabolic risks are significantly increased in NWO population,and such risks persist after excluding the effect of abdominal obesity.This study suggests that NWO,a subtype of obesity,may provide more information about the cardiometabolic risks compared with the traditional obesity types based on BMI or WC.Part 4 Normal weight obesity and risk of diabetes in Shaanxi province,northwestern China: a population-based cohort studyIn the past three decades,obesity has become a global epidemic that threatens public health.Obesity confers substantial excess risk for morbidity and mortality,particularly from diabetes and cardiovascular diseases.The concept of obesity subtypes draws lots of attention.A phenotype,called “normal weight obesity”(NWO),has been introduced,which describes those individuals with normal body mass index(BMI)but increased percent of body fat(BF).The most recent study on NWO focused on the association with diabetes,but there was almost no cohort study.Therefore,cohort studies focusing on the NWO with the risk of diabetes were needed.We conducted a population-based cohort study,aiming to evaluate the risk of developing diabetes in the Chinese population with NWO.AimsThe term of NWO describes those individuals with normal body mass index(BMI)but had increased percent of body fat percentage(BF%).We aimed at evaluating the risk of developing diabetes in Chinese population with NWO.MethodsThe population-base cohort study,which was held in Xi'an,Northwestern China,was based on China National Diabetes and Metabolic Disorders Survey.Among 1915 subjects at baseline,806 subjects agreed and completed a 5-year follow-up examination.693 non-diabetic subjects were included as study sample.BF% was assessed by electrical bioimpedance.NWO was defined as subjects with a normal BMI(18.5-23.9 kg/m2)and excess in BF%(?24% in men and ?33% in women).Diabetes was diagnosed based on oral glucose tolerance test.ResultsAmong 693 individuals,37(5.34%)developed diabetes during the follow-up period.Total 293 individuals were diagnosed as normal weight healthy controls,68(9.81%)were diagnosed as NWO,and 332 were diagnosed as overweight and obesity(BMI ? 24 kg/m2).The cumulative incidence of diabetes in normal weight healthy controls,NWO people,and overweight people was 2.39%(7cases),5.88%(4cases)and 7.83%(26cases),respectively.Cox proportional hazard regression showed that the multivariable-adjusted relative risk of diabetes in the NWO people and overweight people were 2.393(95%CI:0.687-8.335,P = 0.171)and 2.537(95%CI:1.085-5.928,P = 0.032),respectively,compared with those in normal weight healthy controls.ConclusionsThe incidence rate of diabetes in Chinese people with NWO is increased.Chinese people with overweight and obesity have higher risks of developing diabetes.In clinical practice,we suggest using simple methods to measure BF% in Chinese population.Part 5 Association between Normal Weight Obesity and Exposure to the Great Chinese Famine of 1959–1962: A Nationwide StudyManmade famine may lead to long-term malnutrition in different age groups(particularly during the early years of life),thereby providing a unique opportunity to test this hypothesis.However,current available studies about the relationship between childhood malnutrition owing to human famine and the risk of metabolic disease in adulthood have inconsistent findings.Therefore,we analyzed the data obtained from the 2007–2008 CNDMDS,also investigated the risk of NWO among individuals who were exposed to the Great Chinese Famine in the prenatal stage,childhood,adolescence,and adulthood,to validate the DOHa D hypothesis.AimsThe developmental origins of health and disease(DOHa D)hypothesis states that poor environmental influences in early life may be risk factors for metabolic disease in later life.The Great Chinese Famine during 1959-1962 provides unique opportunities to testify this hypothesis.MethodsWe analyzed the data which were obtained from the 2007-2008 CNDMDS.Total 25,796 subjects(10,174 males and 15,622 females)who were born before December 1965 were included.Participants were categorized into seven exposure groups: famine-unexposed group,fetal-exposed group,early childhood-exposed group,mid childhood-exposed group,late childhood-exposed group,adolescence-exposed group,and adulthood-exposed group.We defined NWO as a normal BMI(18.5–23.9 kg/m2)but with excess BF%.The cut-off values of BF%(?24% for males and ?33% for females)reported in our previous study were used as the diagnostic criteria for excess BF%.ResultsIn men,the prevalence of NWO is 5.56%,5.30%,5.13%,4.38%,4.72% and 4.52.In women,the prevalence of NWO is 2.56%,2.88%,3.47%,3.30%,3.91% and 3.26%.In both males and females,there is no significant difference statistically among all groups.Logistics regression analyses showed that the risk of NWO was not significantly increased in all famine-exposed groups compared with the unexposed group in males and females.The risk of NWO was not significantly increased in severe and less severe famine-exposed groups compared with the unexposed group in males and females(all P >0.05).ConclusionDOHa D hypothesis cannot satisfactorily explain the finding that the risk of NWO increases in adulthood among populations who were exposed to famine in early life.