Obesity phenotypes and subclinical cardiovascular diseases in a mixed‐ancestry South African population: A cross‐sectional study (南非混合血统人群的肥胖表型与亚临床心血管疾病：一项横向研究)

Abstract

Keywords: cardiovascular risk factors, obesity phenotype, South Africa, sub-clinical cardiovascular disease.Efforts to characterize the disease risk associated with obesity 1 suggest that related metabolic abnormalities are not uniform in all obese persons. The concepts of "metabolically-healthy-" and "metabolicallyabnormal-" normal-weight, overweight and obese have been used to characterize the phenotypes resulting from the cross-classification of individuals by body mass index (BMI) and metabolic status. 2 Studies, mostly from developed countries, suggest each phenotype to represent a sizable proportion of the population. However, evidence on their association with cardiovascular disease (CVD) risk is inconclusive, and no study has assessed the prevalence of obesity phenotypes and correlation with disease risk in Africans. 3 We assessed the prevalence of obesity phenotypes, and their association with sub-clinical CVD in mixed-ancestry South Africans. MethodsParticipants were from the Bellville-South community in Cape Town, as described elsewhere. 4,5 Based on BMI (weight [kg]/height [m 2 ]), participants were classified as normal-weight (BMI, <25.0), overweight (BMI, 25.0-29.9), or obese (BMI, ≥30.0). The metabolic status was considered abnormal if two or more of the following: (i) systolic (or diastolic) blood pressure ≥130 (85) mmHg, or history of doctor-diagnosed hypertension;(ii) fasting blood glucose ≥5.6 mmol/L or diabetes mellitus (known/screen-detected using oral glucose tolerance test); (iii) serum triglycerides ≥1.69 mmol/L; and (iv) high-density lipoprotein (HDL)-cholesterol <1.04 mmol/L for men (<1.29 mmol/L women). Crossclassification of participants by BMI and metabolic status resulted in the following categories: normalweight metabolically-healthy (NWMH), overweight metabolically-healthy (OvMH), obese metabolicallyhealthy (OMH), normal-weight metabolic-abnormal (NWMA), overweight metabolically-abnormal (OvMA), and obese metabolically-abnormal (OMA).Sub-clinical CVD was based on the common carotid intima-media thickness (CIMT) and the cardiac interventricular septum (IVS) thickness. CIMT was measured by qualified sonographer observers, in longitudinal section at the far wall of the distal common carotid arteries, at three consecutive end-points, 5-10 mm apart. The median of the six readings (three from each side) was calculated for each participant using a portable B-mode and spectral Doppler ultrasound scanner. The same device was used to measure the telediastolic IVS thickness based on B-mode images.The Cochrane-Armitage trend test and modified Brown-Forsythe Levene-type procedures were used to investigate the linear trend of baseline characteristics across BMI categories overall, and by metabolic status. The R statistical software version 2.13.0 (13-04-2011), (The R Foundation for Statistical Computing, Vienna, Austria) was used for all statistical analyses. ResultsThe starting sample comprised 574 individuals examined in 2011; 235 (40.9) did not consent for the CIMT meaCorrespondence

The Distribution of Obesity Phenotypes in HIV-Infected African Population

“…A better proxy for visceral adipose tissue is WC and, unsurprisingly, within BMI categories, participants with compared to without metabolic abnormalities had greater WC and elevated HOMA-IR index, a proxy measure of insulin resistance. Similar findings have also been reported in other studies [ 20 , 23 , 24 , 25 ]. Recent studies in Caucasians that have included insulin resistance among abnormal metabolic traits, have reported high prevalence of metabolically abnormal phenotypes both in obese and non-obese people [ 26 , 27 ].…”

“…The distribution of body size phenotypes in our study is comparable with results of local studies conducted in the general population in South Africa [ 24 , 28 ]. Our previous community-based study in mixed-ancestry adults in Cape Town applying the same definition criteria found OMH and NWMA to be present respectively 16.5% and 5% of the sample [ 24 ].…”

“…The distribution of body size phenotypes in our study is comparable with results of local studies conducted in the general population in South Africa [ 24 , 28 ]. Our previous community-based study in mixed-ancestry adults in Cape Town applying the same definition criteria found OMH and NWMA to be present respectively 16.5% and 5% of the sample [ 24 ]. Furthermore, among normal-weight participants (17.1% of the sample), 29.1% were classified as metabolically abnormal, while among obese participants (53.7% of the sample), 30.8% were classified as metabolically healthy [ 24 ].…”

Obesity phenotypes in urban and rural Cameroonians: a cross-sectional study

“…Our study is among the firsts to examine the concept of metabolically healthy obesity in African populations, and is relevant to the ongoing debate on the usefulness of this concept. The prevalence of body size phenotypes among African populations including the urban rural differences, have seldom been investigated in studies [ 6 ]. Compared to studies conducted in other continents, and despite differences in the definitions of “metabolically healthy” that have been used, the prevalence of metabolically healthy obese individuals is similar between the present and previous studies, which found a prevalence of 6 to 75% [ 6 ], depending on the definition used, and higher in population of Asia descend than in Caucasian.…”

“…Despite the increasing prevalence of obesity in Africa population [ 5 ], assessment of the aforementioned body size phenotypes and their implications for disease risk and prognostic have mainly been conducted in Western populations [ 6 ]. Furthermore, few extant studies have examined the frequencies of various phenotypes by ethnicity, with suggestion of higher prevalence of metabolically healthy obesity among Asians populations [ 4 ].…”