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Objective: To conduct a secondary analysis of dietary variety consumed by individuals of African-origin in two countries with differing stages of economic development. Our overall aim is to determine the relationships of two different dietary variety scores developed previously in our laboratory with reported energy intake (rEI), ER (which will be a more accurate reflection of true EI) and BMI in the total sample and the plausibly reporting subsample. Methods: Data for this analysis were collected as part of METS between January 2010 to September 2011, whose purpose was to elucidate the associations of physical activity and diet with body weight, diabetes, and risk of cardiovascular disease. Five communities of African-origin and in different countries were selected based on their different levels of economic development, as measured using the UN Human Development Index. A subsample of 141 (Ghana, n=70 and U.S., n=71) men and women with an average age of 35.1±0.5 years and an average BMI of 27.5±0.6 kg/m2 were randomly selected to have their total energy expenditure (TEE) measured by the doubly labeled water (DLW) method. Participants were interviewed using the multiple-pass method designed by the Medical Research Council of South Africa to estimate their dietary intake the day after consumption. Data was transferred to Nutrient Data System for Research (NDSR) ver. 2011 and dietary variety scores (DVS) were calculated for combination and ingredient varieties. Combination variety was defined as the total number of unique foods and beverages consumed in a day. Ingredient variety was the total number of unique ingredients consumed in a day. Implausibility of rEI was controlled for by calculating rEI as a percentage of TEE. Associations of dietary variety scores with total energy intake and BMI were assessed for both the total sample and plausible subsample using SPSS version 22 through univariate analyses of variance and correlations. Results: Both combination and ingredient variety were positively associated with rEI in both countries when implausible reporting was not controlled, but no significant association was observed in both countries when implausible reporting was controlled. Ingredient variety was negatively associated with TEE when implausible reporting was both controlled and uncontrolled in the U.S. (p= 0.029), but no association was observed in Ghana. Ingredient and combination variety were also negatively associated with log BMI, percent body fat, and weight in U.S. when implausible reporting was not controlled but not in Ghana’s. However, in Ghana, combination variety was positively associated with percent body fat (p=0.041) and log BMI (p= 0.027) when plausible reporting was controlled but was not significant when implausible reporting was uncontrolled. Conclusion: Dietary variety was positively associated with rEI in both countries when implausible reporting was not controlled and with obesity markers in Ghana when plausible reporting was controlled.

An exercise-induced energy deficit may affect post-exercise energy intake, physical activity energy expenditure (PAEE) and energy balance hormones. Therefore, the objective of this thesis was to investigate the impact of a single bout of exercise either of moderate (40% O2max) or high (70% O2max) intensity on post-exercise energy intake, physical activity energy expenditure and energy balance hormones in both sedentary and active males. Physical activity energy expenditure increased between 38 and 62 hours following moderate intensity exercise in sedentary males (Chapters 3 and 4). This was due to increased light intensity energy expenditure (2.4-4.79 METs) such as standing and walking activities (Chapter 4). The Change in PAEE was not associated with circulating leptin and adiponectin concentrations. There was no impact of a single bout of exercise on post-exercise energy intake in sedentary males during a buffet meal (Chapter 4). Chapter 5 aimed to determine whether changes in PAEE, energy intake, and energy balance hormones were related to physical activity status. Interestingly, plasma acylated ghrelin concentration was suppressed while total peptide YY (PYY) concentration tended to be elevated after high intensity exercise in active males (Chapter 5). However, there was no impact of either moderate or high intensity exercise on PAEE and post-exercise energy intake in active males. The final study (Chapter 6) determined whether high intensity exercise in the fed state after a few days of food restriction had an impact on circulating energy balance hormones. Circulating postprandial total PYY and pancreatic polypeptide (PP) were increased for one hour after high intensity exercise in active men. There was no change in PAEE and post-exercise energy intake after exercise.

More than seventy percent of Americans over the age of sixty are classified as overweight or obese, and the future incidence of these conditions is expected to rise. Although it is unclear why older adults are predisposed to weight gain, decreased total energy expenditure may contribute to positive energy balance. It is also possible that age-related impairments in energy intake regulation result in the inability to appropriately adjust food intake to meet energy requirements with advancing age. The purpose of these investigations was to determine the influence of age and habitual physical activity on acute regulation of energy intake. Secondary objectives were to determine if there are sex differences in energy intake regulation, and to determine if pre-meal water consumption decreases meal energy intake in young and older adults. To achieve these objectives, the ability to spontaneously adjust energy intake at a meal under "preloading" conditions in which a yogurt shake or water was consumed prior to the meal was determined. We hypothesized that older adults would demonstrate less accurate energy intake regulation than younger adults, but that energy intake dysregulation would be attenuated in physically active older adults. We also expected that young men would have higher accuracy of energy intake regulation compared to young women matched for dietary cognitive restraint and cardiorespiratory fitness, and that pre-meal water consumption would decrease meal energy intake in young and older adults. Our main finding was that energy intake regulation is significantly impaired in older compared to younger adults, and that habitual physical activity improves short-term, but not acute, energy intake regulation. We also found that young men demonstrate significantly higher accuracy of energy intake regulation compared to young women. Lastly, we determined that pre-meal water consumption significantly decreases meal energy intake in older, but not young, adults. Overall, these results indicate that acute energy intake regulation is less accurate with advancing age, but that regular physical activity improves short-term energy intake regulation. Additionally, sex appears to influence energy intake regulation, and water consumption is a potential strategy to reduce energy intake in older adults. / Ph. D.

The role of gut hormones in the regulation of appetite and food intake is well established. The studies presented within this thesis have examined the effects of exercise and different environmental conditions on gut hormones (acylated ghrelin and total peptide YY), appetite and food intake. Forty-two young (mean ± SEM; 22.6 ± 0.4 y), healthy and generally lean (body mass index 23.7 ± 0.3 kg m2) males were recruited into four studies. In study one, 60 minutes of high intensity (70 % of O2 max) running and cycling exercise suppressed concentrations of the appetite-stimulating hormone acylated ghrelin to a similar extent. Study two revealed that after 60 minutes running in the heat (30 °C), hunger is lower in the pre-prandial period, and energy intake lower over the 7 h trial duration compared with a similar trial conducted in temperate (20 °C) conditions. Acylated ghrelin was suppressed during running in the temperate and hot environment but this did not appear to mediate the lower energy intake observed during the hot trial. In study three, energy intake tended to be higher after 60 minutes running in a cool environment (10 °C) compared with a temperate (20 °C) environment. During and shortly after running in the cold, perceived ratings of fullness and satisfaction were lower. Acylated ghrelin concentrations appeared to be suppressed to a lesser extent during running in the cold which could mediate the elevated energy intake observed at the first meal. However, energy intake was also higher at the second meal in the cold trial when acylated ghrelin concentrations were higher in the temperate trial. Study four showed that energy intake and acylated ghrelin concentrations were lower, and total PYY tended to be lower, in normobaric hypoxia suggesting a possible role for acylated ghrelin, but not PYY, in mediating the decrease in energy intake observed in hypoxia. This thesis confirms that exercise transiently suppresses acylated ghrelin concentrations regardless of the environmental conditions (temperature and altitude) exercise is performed in. The findings support anecdotal reports that appetite and energy intake are suppressed in the heat and stimulated in the cold. These responses may be partly mediated by acylated ghrelin immediately after running but other mechanisms are likely involved thereafter. Acute hypoxic exposure suppresses acylated ghrelin concentrations; an observation which may explain the decreased energy intake in hypoxia.

Glucose is the primary fuel for the brain and also important for exercising muscle. The purpose of the thesis was to investigate the effects of the glycaemic index (GI) of mixed meals on appetite, cognitive performances and metabolic responses during intermittent exercise in recreationally active adults. Study one investigated whether a low GI (LGI) breakfast (GI = 42.5) could suppress appetite and reduce energy intake (EI) of 12 recreationally active females (28.2 ± 8.0 years) more than a high GI (HGI) breakfast (GI = 73.5). Area under the curve of the appetite score (AS AUC) following LGI breakfast was significantly greater than the HGI trial during the 60-min postprandial (pp) period (2568 ± 1027 vs. 2198 ± 821 mm∙min, p = 0.025). The HGI breakfast facilitated a stronger appetite suppressing effect up to eight hours post breakfast than the LGI trial (18834 ± 3906 vs. 21278 ± 3610 mm∙min, p = 0.028). The EI on the LGI trial day was significantly higher than on the pre-trial day (2,215 ± 576 vs. 1,748 ± 464 kcal, corrected p = 0.008). Fourteen recreationally active males (34.5 ± 8.9 years) in study two consumed the LGI (GI = 41.3) and HGI (GI = 74.3) breakfasts in the laboratory and then prescribed LGI and HGI meals in the free living environment. In line with study one, the AS AUC was significantly smaller following HGI than LGI breakfast over the 60-min pp period (2,989 ± 1,390 vs. 3,758 ± 1,290 mm∙min, p = 0.027). The HGI meals (GI = 76.9) suppressed appetite more than the LGI meals (GI = 39.6) over 12 hours on the trial day (35,454 ± 9,730 vs. 41,244 ± 8,829 mm∙min, p = 0.009) although energy balance was not different between trials. Study three investigated whether following a LGI breakfast (GI = 42.2) providing 1 g CHO kg-1 BM could result in a better vigilance and attention than a HGI breakfast (GI = 72.4), and reduced lunch EI in 16 recreationally active males (24.4 ± 3.6 years). A significant trial x time effect in the interference time of the Stroop Colour Word Task (SCWT) (p = 0.039) showed that the LGI breakfast maintained the attentional performance up to 90-min pp. Both high pre-task glucose concentration ([Glucose]) at 15-min pp and low pre-task [Glucose] at 105-min pp in the HGI trial were associated with unfavourable outcomes in vigilance in the Rapid Information Processing Task (RIPT). The LGI pre-task [Glucose] returning back to fasting level at 60-min pp was associated positively with the response time. The pre-lunch AS was a significant predictor of the lunch EI per fat free mass which explained 21% and 26% of variance in the LGI and HGI trials respectively. No significant difference was found in the ad libitum lunch EI between trials. Sixteen recreationally active males (27.8 ± 7.7 years) in study four consumed a LGI (GI = 42) and a HGI breakfast (GI = 72.8) providing 1.2 g CHO kg-1 BM consumed 60 minutes prior to intermittent running on two separate mornings. Better attentional performance at 150-min pp was found following LGI than HGI breakfast. The significant trial x time interaction in the SCWT (p = 0.045) showed the shortest interference time performed after the last exercise session in the LGI trial. The amounts of CHO and fat being oxidized were comparable between trials during three sessions of 16-min intermittent running with an average intensity of 65% V̇O2max. In conclusion, the pre-meal appetite sensation is more predictive of the subsequent meal EI than the pre-meal [Glucose]. The meal strategy for weight management in recreationally active adults may focus on greater appetite suppression by selecting HGI foods whilst maintaining healthy eating guidelines. Recreationally active males performing sports requiring high levels of vigilance and selective attention with low physical activity levels can benefit up to 60–90 min pp from the LGI breakfast. Their attentional performance can benefit from the LGI breakfast with moderate to high intermittent intensities in the late exercise period at 150–min pp. Recreationally active adults should consider the timing of meal consumption in relation to performing intermittent exercise, in order to maximize the advantages from the LGI or HGI breakfasts for cognitive performance or appetite suppression. They may be more liberal in pre-exercise food choices if substrate oxidation during intermittent running is only of their concern.

Current physical activity recommendations are being met by less than 21 % of children between 5-15 y. Recent Government initiatives are aiming to increase children’s participation in exercise. However, the effects on an imposed bout of exercise-induced energy expenditure (EE) on energy intake (EI) and appetite (hunger, fullness and prospective consumption) in normal weight children have received a limited research focus to date. Therefore, this thesis aimed to investigate how an imposed bout of exercise-induced energy expenditure (EE) on energy intake (EI) and appetite in normal weight children The first study investigated whether 17 habitually active girls were able to accurately increase their EI to match the EE following 60 min moderate intensity walking exercise. On average 17% of the EE was compensated for by an increase in EI. However, the ranged for EI change was -160% to +166% indicating large individual responses. The second study investigated whether 30 min of maximal sprint intermittent sprint cycling exercise would significantly alter EI or appetite in 13 boys and 13 girls. In the boys, hunger and prospective consumption were suppressed whilst fullness increased immediately following the exercise, whilst EI was significantly increased in response to the exercise condition. No significant changes to appetite or EI were observed in the girls. The third study investigated whether a mid-morning snack, moderate intensity cycling exercise (energy matched to snack) or both would alter EI or appetite in 20 boys and 18 girls. Irrespective of sex, hunger and prospective consumption were suppressed whilst fullness increased following the mid-morning snack, however this change in appetite did not alter EI as no significant differences were found between conditions. The fourth study investigated whether 99 recreational sports players (males/females, adults/children) were able to conceptualise their EE following 1 h habitual training into quantifiable amounts of food (chocolate) or drink (sports drink). Only 36 % of the EE from the exercise was met by the estimated amounts of food or drink. Age, sex nor sports participation significantly altered the participants’ accuracy of estimation. The fifth study investigated whether sex or dietary restraint impacted brain activation responses to visual food stimuli in 15 boys and 14 girls between a fed and fasted condition. Significant differences in brain activation were found between conditions, sexes and dietary restraint, potentially suggesting the differences observed in the previous experimental studies could be attributed to neurological alterations between participants. In conclusion, the findings presented demonstrate the changes in EI between young adolescents in response to an imposed bout of exercise are extremely variable. Whilst eating behaviours failed to correspond to the EI differences observed between participants, potentially brain activation differences may be responsible. The sex of the participant is more likely to impact EI and appetite following maximal sprint intensity exercise, more so than a bout of moderate intensity exercise. Future research should focus on determining what underpins the variable change in EI between participants following a bout of exercise.

Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

Background: The relationship between eating frequency (EF) and adiposity is surrounded by controversy. Numerous cross-sectional studies have been performed on the subject, yet the results are mixed. While some of these studies show an inverse relationship between EF and adiposity, this is likely due to underreporting of EF and total energy intake when diets are self-reported. In studies where underreporting was taken into account, EF is positively associated with both energy intake and adiposity. Intervention trials have failed to show a significant effect of EF on energy intake or weight change, but only a small number exist. Objective: In this study, we examined associations among EF, energy intake, and adiposity in free living adults consuming self-selected diets. In conducting this analysis, two common methodological problems in this research area were addressed: 1) the lack of consideration of energy balance fluctuations throughout the day, and 2) a tendency not to account for implausible reporting of energy intake. We hypothesized that individuals with higher EF would have higher BMI, percentage body fat, and energy intake. Additionally individuals with greater fluctuations in energy balance will have higher BMI, percentage body fat, and EF. Methods: We performed a secondary analysis of data collected as part of a previous study in our laboratory on diet and energy regulation (unpublished). One hundred and twenty-six participants were enrolled (62.4 % female, and 75.2% Caucasian), and one participant dropped the study due to pregnancy. Mean ±SD age, BMI, and percentage body fat of the remaining 125 participants were 29.8 ±12.2 years, 24.5±3.9 kg/m2, and 27.8±9.8% respectively. We analyzed one day of dietary intake collected using a multiple pass 24 hour recall. Energy intake was calculated by NDS (Nutrition Data System for Research, version 2011 (n=36) and version 2010 (n=89)). An eating occasion was defined as any occurrence of energy intake > 0 kcal separated by at least 1 hour. EF was defined as the number of eating occasions per day. A specifically designed spreadsheet that generates within-day energy balance was used to produce estimates of hourly energy balance. We also used total energy expenditure measured by doubly labeled water and the Huang et al. (2005)1 method to identify implausible reporters (cutoff for plausibility was reported energy intake (REI) within ±16.8% of TEE) and conducted Pearson’s correlations and regression analysis in both the total sample and a subsample in which implausible energy intake reporters were excluded from analysis. Results: We identified 59.2% of the sample as implausible reporters (n=74; 47 under-reported and 27 over-reported). Mean ±SD EF and energy intake were 4.7±1.5 and 2356±964 kcal in the total sample and 4.8±1.6 and 2371±689 kcal in the plausible sample. In the total sample EF was positively correlated to energy intake among women (r=0.244, p=0.032). No other significant relationships were observed between EF and either energy intake, BMI, or percentage body fat, in the total or plausible sample. In the total sample, maximum energy deficit > 400 kcal in a 24 hours period was significantly and positively correlated with percentage body fat (r=0.211,p=0.019) and negatively correlated with EF (r=-0.243, p=0.007) when controlling for sex and age. Separating the sample by sex we observed significant positive correlation between percentage body fat and maximum energy deficit in men (r=0.382, p=0.009) but not in women. No significant relationships between fluctuations in energy balance and percentage body fat were observed in the plausible sample. Conclusion: No evidence was found to suggest a relationship between EF and adiposity. The significant positive relationships observed between maximum energy deficit and adiposity in the total sample are consistent with previous findings. The number of implausible reporters identified in our analysis supports that over and under-reporting is a major issue associated with self-reporting of dietary intake.