Factors affecting energy expenditure and the efficiency of fuel utilization : feeding and exercise models

The first aim of this dissertation was to monitor both rat and human responses to short-term perturbations in energy balance brought about through food energy restriction and refeeding, exercise training and the cessation of exercise training or surgical lipectomy. The second aim of this dissertation was to identify factors which might explain differences in food energy intake in weight-matched, weight-stable "large and small eaters". The final aim of this dissertation was to identify factors which might explain differences in resting energy expenditure in a large sample of weight-stable men and women, including exercising and non-exercising persons, and including persons who may be regarded as "restrained eaters"

From catastrophe to complexity: a novel model of integrative central neural regulation of effort and fatigue during exercise in humans

It is a popular belief that exercise performance is limited by metabolic changes in the exercising muscles, so called peripheral fatigue. Exercise terminates when there is a catastrophic failure of homoeostasis in the exercising muscles. A revolutionary theory is presented that proposes that exercise performance is regulated by the central nervous system specifically to ensure that catastrophic physiological failure does not occur during normal exercise in humans

Development of a four-item physical activity index from information about subsistence living in rural African women: a descriptive, cross-sectional investigation

BACKGROUND:We investigated the criterion validity of a physical activity index (PAI) derived from socio-demographic variables obtained from convenience samples of rural African women. METHODS: We used a sample (N = 206) from a larger dataset which surveyed adult rural Africans during 1997, and data collected during 2003/4 from 138 adult rural African women. A three-point PAI (low-, medium- and high-subsistence) was constructed from four socio-demographic questions related to electricity, cooking methods, water collection and availability of motorized transport. Criterion measures included measures of adiposity, blood biochemistry, resting blood pressure (RBP), physical fitness (VO2max) and single-plane accelerometry (ACC). RESULTS: Age, educational level and health status were not related to PAI level (p > 0.1). There was a significant negative, linear trend between the PAI level and adiposity level (p 0.08, RBP: p > 0.07). CONCLUSION: The PAI derived from a socio-demographic questionnaire is a valid instrument for broadly categorizing levels of physical activity for this specific population of rural African women. As the epidemiological transition progresses, validity will need to be re-established

Validation of a food frequency questionnaire in older South Africans

The International Society for Burns Injuries (ISBI) has published guidelines for the management of multiple or mass burns casualties, and recommends that 'each country has or should have a disaster planning system that addresses its own particular needs.' The need for a national burns disaster plan integrated with national and provincial disaster planning was discussed at the South African Burns Society Congress in 2009, but there was no real involvement in the disaster planning prior to the 2010 World Cup; the country would have been poorly prepared had there been a burns disaster during the event. This article identifies some of the lessons learnt and strategies derived from major burns disasters and burns disaster planning from other regions. Members of the South African Burns Society are undertaking an audit of burns care in South Africa to investigate the feasibility of a national burns disaster plan. This audit (which is still under way) also aims to identify weaknesses of burns care in South Africa and implement improvements where necessary

Accuracy of reporting food energy intake: Influence of ethnicity and body weight status in South African women

The current study sought to identify characteristics that may be associated with the misreporting of food energy intake (EI) in urban South African women. A total of 198 women (61 black, 76 of mixed ancestry, 61 white) completed a quantified food frequency questionnaire, from which daily energy and macronutrient intake were calculated. Body composition (body mass index [BMI], percentage of body fat), body image (Feel-Ideal Difference index and Body Shape questions) and socio-economic status (SES) (household density and asset index) were also measured. Food EI in relation to estimated basal metabolic rate ratio that was less than 1.05 represented under-reporting, whereas a ratio greater than 2.28 represented over-reporting. Results suggested that 26% of the participants under-reported, 64% adequately reported and 10% over-reported. Participants who under-reported had a higher BMI (p < 0.01) and higher percentage of body fat (p < 0.05) than those who adequately and over-reported. The majority of under-reporters were black (38%) versus 21% under-reporters of mixed ancestry and 20% white under-reporters (p < 0.01). Eighty-three per cent of black under-reporters were obese. On the other hand, a majority (63%) of overweight women of mixed ancestry and a majority (50%) of white normal-weight women under-reported their food EI. Under-reporters reported a lower intake of dietary fat (p < 0.01) and a higher intake of dietary protein (p < 0.01) than adequate or over-reporters. Food EI reporting was not influenced by SES or body image. In conclusion, results suggest that food EI reporting is influenced by body size, and may be ethnic-specific in South African women

Effect of body mass and physical activity volume and intensity on pedometry-measured activity energy expenditure in rural black South Africans in the Limpopo Province

Objectives. We developed a novel approach to investigate patterns of pedometry-measured total weekly activity energy expenditure (EEAct) in rural black South Africans in the Limpopo Province. Design. We analysed 7-day pedometry data in 775 subjects (female: N=508; male: N=267). Variance components models for EEAct were used to estimate the variance explained by body mass (BM), total weekly steps (volume) and estimated intensity (kcal. kg-1.step-1). Univariate General Linear Models, adjusting for age, BM and physical activity (PA) volume, were used to determine if EEAct was primarily affected by volume or intensity. Results. BM (13.1%), PA intensity (24.4%) and PA volume (56.9%) explained 94.4% of the variance in EEAct. Adjusted EEAct did not differ between sexes (78 kcal.week-1, p =0.2552). There were no significant differences across activity categories (sedentary to very active) for adjusted EEAct (62 - 287 kcal.week-1, p>0.1). Adjusted EEAct for 6 - 7 days of compliance (≥10 000 steps.day-1) differed significantly from 1 - 2 days of compliance (266 - 419 kcal.week-1, p0.30). Conclusions. We have highlighted an intensity effect for days of compliance and at very active ambulatory levels (≥12 500 steps. day-1). A volume effect appeared to dominate between sexes, across activity categories and weight-by-activity categories. It is important that post hoc statistical adjustments be made for body mass and PA volume when comparing EEAct across groups

Changes in training activity post COVID-19 infection in recreational runners and cyclists

Background: Anecdotal evidence suggests that athletes struggle to return to exercise post COVID-19 infection. However, studies evaluating the effect of COVID-19 on athletes’ exercise activity are limited. Objectives: The objectives of this study were: (i) to describe the perceptions of recreational runners and cyclists recovering from COVID-19 on their training activity and general wellbeing, (ii) to compare device-measured training data in runners and cyclists pre- and post COVID-19, with noninfected controls that had a training interruption. Methods: Participants who were recruited via social media completed an online questionnaire (n=61), including demographic, health and COVID-19 descriptive data. In a sub-sample, device-measured training data (heart rate, time, distance and speed, n=27) were obtained from GPS devices for four weeks before infection and on resumption of training. Similar data were collected for the control group (n=9) whose training had been interrupted but by factors excluding COVID-19. Results: Most participants experienced a mild to moderate illness (91%) that was associated with a training interruption time of two-four weeks. Decreases in heart rate, relative exercise intensity, speed, time and distance were observed during the first week of returning to training for both groups, followed by an increase from Week two onwards. Discussion: Results failed to support a ‘COVID-19 effect’ on exercise activity as reductions in training variables occurred in both the COVID-19 and control groups. A possible explanation for the reductions observed is a deliberate gradual return to training by athletes post-COVID-19. Conclusion: More research is needed using device-measured training data prior to and post COVID-19 infection to better understand the impact of the SARS-CoV-2 virus on the exercise activity of athletes.

Where does the black population of South Africa stand on the nutrition transition?

OBJECTIVE: To review data on selected risk factors related to the emergence of noncommunicable diseases (NCDs) in the black population of South Africa. METHODS: Data from existing literature on South African blacks were reviewed with an emphasis placed on changes in diet and the emergence of obesity and related NCDs. DESIGN: Review and analysis of secondary data over time relating to diet, physical activity and obesity and relevant to nutrition-related NCDs. SETTINGS: Urban, peri-urban and rural areas of South Africa. National prevalence data are also included. SUBJECTS: Black adults over the age of 15 years were examined. RESULTS: Shifts in dietary intake, to a less prudent pattern, are occurring with apparent increasing momentum, particularly among blacks, who constitute three-quarters of the population. Data have shown that among urban blacks, fat intakes have increased from 16.4% to 26.2% of total energy (a relative increase of 59.7%), while carbohydrate intakes have decreased from 69.3% to 61.7% of total energy (a relative decrease of 10.9%) in the past 50 years. Shifts towards the Western diet are apparent among rural African dwellers as well. The South African Demographic and Health Survey conducted in 1998 revealed that 31.8% of African women (over the age of 15 years) were obese (body mass index (BMI) > or = 30kg m(-2)) and that a further 26.7% were overweight (BMI > or = 25 to <30 kg m(-2)). The obesity prevalence among men of the same age was 6.0%, with 19.4% being overweight. The national prevalence of hypertension in blacks was 24.4%, using the cut-off point of 140/90 mmHg. There are limited data on the population's physical activity patterns. However, the effects of the HIV/AIDS epidemic will become increasingly important. CONCLUSIONS: The increasing emergence of NCDs in black South Africans, compounded by the HIV/AIDS pandemic, presents a complex picture for health workers and policy makers. Increasing emphasis needs to be placed on healthy lifestyles

Physical activity, change in blood pressure and predictors of mortality in older South Africans - a 2-year follow-up study

Objective. A 2-year follow-up study of a cohort of 200 historically disadvantaged older South Africans was conducted to: (i) characterise current levels of habitualphysical activity; (ii) relate physical activity to current risk factors for chronic disease; and (iii) identify risk factors associated with 2-year mortality. The baseline sample, drawn in 1993, was found to have a high prevalence of hypertension (71.7%).Research design. Retrospective cohort study.Methods. A baseline sample of 200 persons aged ≥ 65 years, resident in the Cape Peninsula, was randomly drawn by means of a two-stage cluster design. Baseline measurements included: anthropometry, waist/hip ratio, systolic and diastolic blood pressure, body mass index (BMI), serum albumin, serum ferritin, haemoglobin and fasting plasma glucose levels, plasma lipid profiles, oral glucose tolerance test and self-reported health status. Subjects were revisited after 2 years, at which time an adapted version of the Yale Physical Activity Survey was administered and measurements of blood pressure and anthropometry were repeated.Statistical analyses. Spearman's rank-order correlations were used to describe relationships between various current risk factors and physical activity. Logistic regression was used to detennine predictors of 2-year mortality from baseline data.Results. At follow-up, 142 of the SUbjects (66 men, 76 women) were traced and measurements collected. Thirty-two subjects were reported to have died by relatives living in the same household (22 men, 10 women). Levels of reported physical activity in the survivors were two-thirds lower than those reported in a sample of North Americans of similar age. There was an inverse association between age and physical activity (r = -0.31; P &lt; 0.0005) and a positive association between BMI and physical activity  (r = -0.29; P &lt; 0.0005). There was, however, no association between physical activity and systolic or diastolic blood pressure. In men, BMI in the lower tertile (P = 0.07) and serum albumin levels were positively associated with increased mortality. Serum albumin levels were protective over the 2-year follow-up period (OR = 0.85; P &lt; 0.05). In women, being diabetic (OR =4.88; P =0.06) and having a waist/hip ratio in the upper tertile (OR =3.26; P =0.06) were associated with mortality.Conclusions. Physical activity levels in this sample of older historically disadvantaged South Africans were habitually low. Simple anthropometric assessments incorporating weight and waistlhip ratio, together with serum albumin measurements, may be useful to screen general health risk for older adults at primary care level and provide indications for social or medical intervention. Further, strategies for earlier detection and effective management of diabetes, particularly in older women, may reduce premature mortality in this population

Physical activity, change in blood pressure and predictors of mortality in older South Africans - a 2-year follow-up study

Objective. A 2-year follow-up study of a cohort of 200 historically disadvantaged older South Africans was conducted to: (i) characterise current levels of habitual physical activity; (ii) relate physical activity to current risk factors for chronic disease; and (iii) identify risk factors associated with 2-year mortaJity. The baseline sample, drawn in 1993, was found to have a high prevalence of hypertension (71.7%). Research design. Retrospective cohort study. Methods. A baseline sample of 200 persons aged ;:;.. 65 years, resident in the Cape Peninsula, was randomly drawn by means of a two-stage cluster design. Baseline measurements included: anthropometry, waist/hip ratio, systolic and diastolic blood pressure, body mass index (BMI), serum albumin, serum ferritin, haemoglobin and fasting plasma glucose levels, plasma lipid profiles, oral glucose tolerance test and self-reported health status. SUbjects were revisited after 2 years, at which time an adapted version of the Yale Physical Activity Survey was administered and measurements of blood pressure and anthropometry were repeated. Statistical analyses. Spearman\u27s rank-order correlations were used to describe relationships between various current risk factors and physical activity. Logistic regression was used to detennine predictors of 2-year mortality from baseline data. Results. At follow-up, 142 of the SUbjects (66 men, 76 women) were traced and measurements collected. Thirtytwo subjects were reported to have died by relatives liVing in the same household (22 men, 10 women). Levels of reported physical activity in the survivors were two-thirds lower than those reported in a sample of North Americans of similar age. There was an inverse association between age and physical activity (r = --{).31; P \u3c 0.0005) and a positive association between BMI and physical activity (r = 0.29; P \u3c 0.005). There was, however, no association between physical activity and systolic or diastolic blood pressure. In men, BMI in the lower tertile (P = 0.07) and serum ferritin levels were positively associated with increased mortality. Serum albumin levels were protective overthe 2-year follow-up period (OR = 0.85; P \u3c 0.05). In women, being diabetic (OR =4.88; P =0.06) and having a waistlhip ratio in the upper tertile (OR =3.26; P =0.06) were associated with mortality. Conclusions. Physical activity levels in this sample of older historically disadvantaged South Africans were habitually low. Simple anthropometric assessments incorporating weight and waistlhip ratio, together with serum albumin measurements, may be useful to screen general health risk for older adults at primary care level and provide indications for social or medical intervention. Further, strategies for earlier detection and effective management of diabetes, particularly in older women, may reduce premature mortality in this population