Sugar-sweetened beverage intake and relative weight gain among South African adults living in resource-poor communities: longitudinal data from the STOP-SA study.

OBJECTIVES: This study examines the prospective association between sugar-sweetened beverages (SSB) consumption and change in body weight over a 4-5-year period in a socio-economically disadvantaged South African population. METHODS: This is a longitudinal study involving 800 adults (212 men, 588 women); 247 from the original METS (Modelling the Epidemiological Transition Study) cohort (N = 504) and 553 of the original 949 members of the PURE (Prospective Urban and Rural Epidemiology) Study. Both cohorts were drawn from low-income, socio-economically disadvantaged communities. Mean follow-up duration and age were 4.5 (SD 0.45) and 50.0 (SD 11.8) years, respectively. Harmonised measurements included body mass index, self-reported moderate-to-vigorous physical activity, and intake of meat, snacks and 'take-aways', fruits and vegetables and SSB (in servings/week). Multivariate logistic regression models were developed to determine the extent to which SSB consumption predicted relative weight gain, after controlling for potential confounders and known predictors. RESULTS: Nearly a third (29%) of participants had a relative weight change ≥5.0%; higher in the non-obese compared to the obese group (32% vs. 25%; p = 0.026). The average SSB consumption was 9.9 servings/week and was higher in the food insecure compared to the food secure group (11.5 vs. 9.0 servings/week; p = 0.006); but there were no differences between women and men (10.3 vs. 9.1 servings/week; p = 0.054). Mean SSB consumption was higher in the group who gained ≥5% weight compared to those who did not (11.0 vs. 8.7; p = 0.004). After adjustment, SSB consumption of 10 or more servings/week was associated with a 50% greater odds of gaining at least 5% body weight (AOR: 1.50, 95% CI (1.05-2.18)). CONCLUSION: These results show that higher intake of SSB predicts weight gain in a sample of South Africans drawn from low-income settings. Comprehensive, population-wide interventions are needed to reduce SSB consumption in these settings.

Prediction of fat-free mass using bioelectrical impedance analysis in young adults from five populations of African origin.

BACKGROUND/OBJECTIVES: Bioelectrical impedance analysis (BIA) is used in population and clinical studies as a technique for estimating body composition. Because of significant under-representation in existing literature, we sought to develop and validate predictive equation(s) for BIA for studies in populations of African origin. SUBJECTS/METHODS: Among five cohorts of the Modeling the Epidemiologic Transition Study, height, weight, waist circumference and body composition, using isotope dilution, were measured in 362 adults, ages 25-45 with mean body mass indexes ranging from 24 to 32. BIA measures of resistance and reactance were measured using tetrapolar placement of electrodes and the same model of analyzer across sites (BIA 101Q, RJL Systems). Multiple linear regression analysis was used to develop equations for predicting fat-free mass (FFM), as measured by isotope dilution; covariates included sex, age, waist, reactance and height(2)/resistance, along with dummy variables for each site. Developed equations were then tested in a validation sample; FFM predicted by previously published equations were tested in the total sample. RESULTS: A site-combined equation and site-specific equations were developed. The mean differences between FFM (reference) and FFM predicted by the study-derived equations were between 0.4 and 0.6 kg (that is, 1% difference between the actual and predicted FFM), and the measured and predicted values were highly correlated. The site-combined equation performed slightly better than the site-specific equations and the previously published equations. CONCLUSIONS: Relatively small differences exist between BIA equations to estimate FFM, whether study-derived or published equations, although the site-combined equation performed slightly better than others. The study-derived equations provide an important tool for research in these understudied populations.

Energy expenditure in young adult urban informal settlement dwellers in South Africa.

Obesity prevalences are increasing in industrialized and developing countries. As a pilot for a comparative study of physical activity and weight change, we assessed energy expenditure (EE) in young black South African adults living in an urban informal settlement. Total EE (TEE) was assessed using doubly labeled water, activity EE (AEE) and activity patterns by accelerometry and body composition by isotope dilution. Twenty young women and eight men were enrolled. Over 50% of the women and no men were obese (mean BMI 31.0 and 21.6 kg/m(2), respectively). Women had significantly lower TEE and AEE after adjustment for body size, as well as lower levels of moderate and vigorous activity. Neither TEE nor AEE was associated with BMI or percent body fat, whereas percent time in vigorous activity was modestly negatively associated with adiposity. These data add to the small literature on EE and activity among populations undergoing epidemiologic transitions.

Total daily energy expenditure in black and white, lean and obese South African women.

BACKGROUND/OBJECTIVES: In South Africa (SA), the prevalence of obesity in women is 56%, with black women being most at risk (62%). Studies in the United States have demonstrated ethnic differences in resting (REE) and total daily energy expenditure (TDEE) between African American (AA) and their white counterparts. We investigated whether differences in EE exist in black and white SA women, explaining, in part, the ethnic obesity prevalence differences. SUBJECTS/METHODS: We measured REE, TDEE and physical activity EE (PAEE) in lean (BMI <25 kg m(-2)) and obese (BMI >30 kg m(-2)) SA women (N=44, 30+/-6 year). REE, TDEE, PAEE and total awake EE were measured during a 21 h stay in a respiration chamber. RESULTS: Black and white subjects within obese and lean groups were not significantly different for age, mass, BMI and % body fat. However, fat-free mass (kg FFM) was consistently lower in the black women (P<0.01) in both weight groups. After adjusting EE measurements for differences in FFM, REE was not significantly different for either body weight or ethnicity, although 24 h TDEE (kJ) was significantly greater in the obese women (P<0.01) and white women (P<0.05). Total awake non-PAEE was not significantly different for either groups, while total awake time was only significantly lower for the lean groups (P<0.01). Total PAEE (kJ min(-1)) was significantly lower in the lean (P<0.001) and black groups (P<0.01). CONCLUSIONS: In this sample of matched, lean and obese, black and white SA women, differences in TDEE were largely explained by ethnic differences in PAEE, and were not as a result of ethnic differences in REE.

BMI, fat and muscle differences in urban women of five ethnicities from two countries.

OBJECTIVE: To investigate body composition differences, especially the relationship between body mass index (BMI) and percent body fat (%BF), among five ethnic groups. DESIGN: Cross-sectional. SUBJECTS: Seven hundred and twenty-one apparently healthy women aged 18-60 years (BMI: 17.4-54.0 kg/m(2)) from South Africa (SA, 201 black, 94 European) and New Zealand (NZ, 173 European, 76 Maori, 84 Pacific, 93 Asian Indian). MEASUREMENTS: Anthropometry, including waist circumference, and total, central and peripheral body fat, bone mineral content and total appendicular skeletal muscle mass (ASMM) derived from dual X-ray absorptiometry. RESULTS: Regression analysis determined that at a BMI of 30 kg/m(2), SA European women had a %BF of 39%, which corresponded to a BMI of 29 for SA black women. For a BMI of 30 kg/m(2) in NZ Europeans, equivalent to 43% body fat, the corresponding BMIs for NZ Maori, Pacific and Asian Indian women were 34, 36 and 26 kg/m(2), respectively. Central fat mass was lower in black SA than in European SA women (P<0.001). In NZ, Pacific women had the lowest central fat mass and highest ASMM, whereas Asian Indian women had the highest central fat mass, but lowest ASMM and bone mineral content. CONCLUSIONS: The relationship between %BF and BMI varies with ethnicity and may be due, in part, to differences in central fatness and muscularity. Use of universal BMI or waist cut-points may not be appropriate for comparison of obesity prevalence among differing ethnic groups, as they do not provide a consistent reflection of adiposity and fat distribution across ethnic groups.

[Pathology related to altitude]. / La pathologie liée à l'altitude.

Low atmospheric pressure at high altitude causes a reduction of partial oxygen pressure in the air. Resulting hypoxia triggers adaptive mechanisms to maintain oxygen delivery to cells at levels compatible with requirements of the body. Hyperventilation and tachycardia followed by polyglobulia are the main physiological responses. Hypoxia-related events can lead to edema of certain organs. Acute mountain sickness, high altitude pulmonary and cerebral edema are potentially serious disorders in remote areas. Since the only remedy is descending to lower altitudes, early recognition of symptoms while return is still possible is important. Use of a portable hyperbaric chamber can be an alternative if return is impossible. The potentially serious consequences of these diseases and poor effectiveness of treatment modalities underscore the need for prevention. The main preventive measures are screening to identify subjects at risk and providing information to mountaineers.

[Cardiovascular effects of a calcium channel blocker in hypoxia caused by altitude]. / Effets cardiovasculaires d'un bloqueur calcique en hypoxie d'altitude.

OBJECTIVE: High altitude pulmonary oedema can be successfully treated and prevented by calcium channel blockers. Moreover, calcium entering in the cells could explain the congestive phenomena of acute mountain sickness (AMS). These findings led us to study the action of a calcium channel blocker, isradipine, in the prevention of non-complicated AMS. METHODS: In a double blind randomized study, 20 healthy volunteers received 5 mg of isradipine (n = 6) or placebo (n = 6) for 8 days. After 5 days of treatment in normoxia, the subjects were rapidly transported to an altitude of 4350 m. The efficiency of the treatment was then estimated by the AMS symptom score, haemodynamic parameters and renal function. RESULTS: The administration of isradipine did not significantly modify AMS symptom score nor most of other parameters measured in high altitude hypoxia. Heart rate was an average of 15 b/min lower in the isradipine group, probably because of a direct action of isradipine on the sinus node. Otherwise, the effects of hypoxia were similar in both groups and were in accordance with the literature. There was no clear explanation for the increase in cardiac output and stroke volume when the subjects moved from supine to standing position. Renal blood flow, measured by Doppler or para-aminohippuric acid clearance was not modified by hypoxia. Cerebral blood flow was elevated, due to the direct vasodilator effect of hypoxia. However this increase did not seem to be the main mechanism responsible for the congestive phenomena. On the other hand, the increase in capillary permeability (demonstrated by the increased transcapillary escape rate of albumin, and albuminuria) appeared to play a major role in the pathogenesis of AMS and high altitude cerebral oedema. Isradipine had no protective effect on these phenomena and its use should be restricted to the treatment of high altitude pulmonary oedema.