No description available.

abstract: ABSTRACT Background. College students’ modifiable health behaviors, including unhealthful eating patterns, predispose them to risk for future cardiometabolic conditions. Purpose. This novel 8-week randomized control parallel-arm study compared the effects of a daily 18-hour Time-Restricted Feeding protocol vs. an 8-hour fast on diet quality in college students. Secondary outcomes were resting morning blood pressure, biomarkers of glucose regulation, biomarkers of lipid metabolism, and anthropometric measures. Methods. Eighteen healthy college students (age = 23 ± 4 years; BMI = 23.2 ± 2.3 kg/m2; MET = 58.8 ± 32.9 min/wk) completed this study. Participants were randomized to a daily 18-hour fasting protocol (Intervention; n = 8) or a daily 8-hour fasting protocol (Control; n = 10) for eight weeks. One ‘cheat’ day was permitted each week. Outcomes were measured at weeks 0 (baseline), 4, and 8. A non-parametric Mann Whitney U test was used to compare the week 4 change from baseline between groups. Statistical significance was set at p≤0.05. Results. Diet quality (p = 0.030) and body weight (p = 0.016) improved from baseline to week 4 for the INV group in comparison to the CON group. The data suggest these improvements may be related to reductions in snacking frequency and increased breakfast consumption. Fasting blood glucose and hip circumference tended to improve for the INV group in comparison to the CON group (p = 0.091 and p = 0.100). However, saturated fat intake tended to increase in the INV group in comparison to the CON group (p = 0.064). Finally, there were no treatment differences between groups (p>0.05) for the 4-week change in total calories, dietary vitamin C, added sugars, resting systolic blood pressure, resting diastolic blood pressure, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), low-density lipoprotein (LDL) cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, waist circumference, or MET. Conclusion. These data, although preliminary, suggest that the 18-hour fasting protocol was effective for improving diet quality and reducing weight in comparison to the 8-hour fasting protocol in healthy college students. Future intervention trials will need to confirm these findings and determine the long-term relevance of these improvements for health outcomes. / Dissertation/Thesis / Doctoral Dissertation Nutrition 2020

Purpose: The purpose of this study was to determine whether time-restricted feeding (TRF) was an effective dietary strategy for reducing fat mass and preserving fat-free mass while evaluating potential changes in cardiometabolic biomarkers, hormones, muscle performance, and energy and macronutrient intake after eight weeks of aerobic exercise and resistance training in overweight and obese adults. Methods: This study was a randomized, controlled trial. Sedentary, overweight and obese adults (mean ± SD; age: 44.48 ± 7.28 years; BMI: 29.61 ± 2.62 kg/m2; females: 85.71%; males: 14.29%) were randomly assigned to a TRF or normal feeding (NF) dietary strategy group. The TRF group consumed all calories between 1200 and 2000 hours, whereas the NF group ate their typical diet. All groups completed eight weeks of aerobic exercise and supervised resistance training. Body composition, muscle performance, energy and macronutrient intake, physical activity, and physiological variables were assessed week zero and week nine. Results: A total of 21 participants completed the study (NF: n = 10; TRF: n = 11). A mild energy restriction was seen for the TRF (~300 kcal/day, 14.0%) and NF (~250 kcal/d, 11.0%) groups between baseline and week seven. Losses of total body mass were significantly greater for TRF (3.3%) relative to NF (0.2%), of which TRF had significantly greater losses of fat mass (9.0%) compared to NF (3.3%) despite similar reductions in energy intake. Lean mass increased across the intervention for both TRF (0.6%) and NF (1.9%), with no group differences. Conclusion: These data support the use of TRF and concurrent exercise training as a short-term dietary strategy for reducing fat mass and preserving lean mass in overweight and obese adults.

No description available.

Nosso grupo de pesquisa estuda ritmos circadianos em um roedor subterrâneo do gênero Ctenomys, o tuco-tuco. Nesta tese, apresentarei dados sobre sincronização fótica e não-fótica dos ritmos circadianos em tuco-tucos, e sobre sincronização não-fótica em camundongos. Investigamos a sincronização fótica em tuco-tucos por meio de uma abordagem conjunta de campo e laboratório. Inicialmente medimos o ciclo claro/escuro natural percebido por animais mantidos em áreas cercadas em campo, utilizando aparelhos light loggers que registraram continuamente o padrão temporal diário da exposição à luz. Em seguida, foi aplicado um modelo desse padrão de exposição à luz em laboratório, para testar o seu potencial como um sincronizador fótico dos ritmos circadianos dos tuco-tucos. O modelo consistiu em pulsos de luz aplicados uma vez por dia em diferentes momentos aleatórios. Apesar de carregar o mínimo de informação temporal, esse regime luminoso foi um sincronizador eficiente em muitos casos, tal como previsto anteriormente a partir de simulações computacionais de um oscilador matemático. Os resultados revelam que a sincronização de osciladores circadianos é ainda mais robusta do que se imaginava. Nosso segundo conjunto de experimentos avaliou a sincronização não-fótica em tuco-tucos, os quais são herbívoros, expostos a ciclos diários de disponibilidade de alimentos. Semelhante a outras espécies de roedores, tuco-tucos desenvolveram uma atividade antecipatória ao alimento, expressa diariamente antes da alimentação. Houve, no entanto, grande variabilidade inter-individual na expressão da atividade antecipatória, provavelmente relacionada com diferenças nas respostas metabólicas à restrição temporal do alimento. O trabalho final foi uma colaboração com o Dr. Shin Yamazaki, sobre sincronização não-fótica em camundongos do tipo selvagem e camundongos mutantes com ablação genética do relógio circadiano. Ciclos diários de alimentos palatáveis e de corrida em roda induziram ritmicidade autossustentada em camundongos mutantes arrítmicos, que não expressavam os genes Period, componentes importantes da maquinaria molecular que gera os ritmos circadianos nas células. Estes resultados sugerem a existência de novos osciladores circadianos que respondem a sinais diários de recompensa. Enquanto espécies modelo de laboratório, tais como o camundongo, podem trazer informações valiosas sobre os mecanismos fisiológicos, as espécies selvagens como o tuco-tuco podem nos dar pistas sobre o significado ecológico dos fenômenos circadianos / Our research group studies circadian rhythms in a subterranean rodent from the genus Ctenomys, the tuco-tuco. In this thesis, I will present data on photic and non-photic synchronization of circadian rhythms in tuco-tucos, as well as a study on non-photic synchronization in the laboratory mouse. Natural photic synchronization in tuco-tucos was verified with field and laboratory approaches. We initially measured the natural light/dark cycle experienced by tuco-tucos in semi natural field enclosures, by means of automatic light logger devices that continuously recorded the daily temporal pattern of light exposure. Next, a model of this light exposure pattern was applied to tuco-tucos in the laboratory, to test its potential as a photic synchronizer of the circadian rhythms. The model consisted of single light pulses applied once a day at varying random times. Despite the minimal timing information, this light regimen was a successful synchronizer in many instances, as predicted from previous computer simulations of a mathematical oscillator. These results revealed that the synchronization of circadian oscillators is even more robust than previously thought. Our second set of experiments evaluated the non-photic synchronization in the herbivorous tuco-tucos, by exposing animals to daily cycles of food availability. Similar to other rodent species, tuco-tucos in this protocol developed a circadian food anticipatory activity (FAA) right before the daily feeding time. However, there was great interindividual variability in FAA expression, likely related to differences in the metabolic responses to time-restricted feeding. The final work was a collaboration with Dr. Shin Yamazaki from the University of Texas Southwestern Medical Center, regarding non-photic synchronization in wildtype and mutant mice with genetic disruption of the circadian clock. Daily cycles of palatable food and wheel running induced self-sustaining rhythmicity in arrhythmic mutant mice, which do not express the Period genes, key components of the molecular machinery responsible for circadian rhythm generation within the cells. These results suggest the existence of novel circadian oscillators responsive to daily rewarding signals. While model laboratory species such as the mouse can bring valuable information on physiological mechanisms, wild species like the tuco-tuco can give us insights into the ecological meaning of circadian phenomena

Responses in growth rate, food conversion efficiency, carcass composition, residual food intake, meat quality and reproduction traits to selection in pigs for four years, for high or low post-weaning growth rate on a fixed but restricted ration were measured in progeny grown on either restricted, ad libitum individual or ad libitum group feeding regimens. Genetic and phenotypic correlations among the traits were also examined on animals whose full pedigrees comprised a total of 5324 animals. Substantial divergent response was achieved from selection for high vs. low growth rate on restricted feeding, with the genetic means of daily gain diverging by 81.25 g or 2.78 genetic standard deviations (SigmaG). The high and low growth rate lines also differed in ultrasonic backfat and food conversion efficiency by 1.12 SigmaG and 0.84 SigmaG, and by 0.88 SigmaG, 1.10 SigmaG, and 1.14 SigmaG for carcass weight daily gain, carcass fat and lean percentage, respectively. These responses were consistent with the moderately to highly, favourable genetic correlations among and between performance and carcass composition traits. Genetic changes in growth rate, ultrasonic backfat, food conversion ratio, carcass daily gain, carcass fat and lean percentage when measured on ad libitum individual feeding were all economically beneficial. The high growth line had a significantly lower voluntary daily food intake and residual food intake than the contemporaneous low line, indicating a reduced energy requirement for maintenance in the high relative to the low line. Genetic correlations between either growth rate or backfat and carcass traits were favourable but unfavourable between daily food intake and carcass fat or lean percentage, implying that selection strategies which place emphasis on increased leanness and decreased fatness would result in a decline in voluntary food intake of the animals. The descendants of breeding pigs selected for high post-weaning daily gain on restricted feeding showed significantly increased growth rates, slaughter weights and carcase lean percentages and reduced fatness when grown in group housing with ad libitum feeding. This suggests that restricted feeding is an effective performance testing approach for seedstock lines supplying commercial regimens with group housing and ad libitum feeding. Carcase lean pH values measured 24 hours post-mortem (pH24) were not statistically different between the selected lines, suggesting that an increase in basal metabolic rate due to increased rate of lean deposition in the high relative to the low line may have been compensated for by a reduction in heat production from other sources such as physical activity. Such a reduction was evidenced by a lower residual food intake in the high than the low growth lines. This supports the hypothesis that selection for high growth rate on restricted feeding does not have detrimental effects on pork quality. The sows of the high growth line produced more piglets with significantly heavier weights at birth, giving a potential for better post-natal growth and higher yield of pork weaned per sow per year than the low growth sows. Body weights of the high line sows prior to mating were also significantly higher than those of low line sows suggesting earlier age of sexual maturity. A non-significant tendency for high line sows to have a lower voluntary food intake than low line sows pointed to the possibility that their lower maintenance requirement as growers was carried over to the lactational phase of life. It is concluded that selection for high growth rate on a restricted ration of fixed amount will produce pig strains with a high genetic potential for lean growth, reduced energy requirement for maintenance and improved reproductive performance, and which will be suitable for growing under a wide range of commercial feeding environments.

Responses in growth rate, food conversion efficiency, carcass composition, residual food intake, meat quality and reproduction traits to selection in pigs for four years, for high or low post-weaning growth rate on a fixed but restricted ration were measured in progeny grown on either restricted, ad libitum individual or ad libitum group feeding regimens. Genetic and phenotypic correlations among the traits were also examined on animals whose full pedigrees comprised a total of 5324 animals. Substantial divergent response was achieved from selection for high vs. low growth rate on restricted feeding, with the genetic means of daily gain diverging by 81.25 g or 2.78 genetic standard deviations (SigmaG). The high and low growth rate lines also differed in ultrasonic backfat and food conversion efficiency by 1.12 SigmaG and 0.84 SigmaG, and by 0.88 SigmaG, 1.10 SigmaG, and 1.14 SigmaG for carcass weight daily gain, carcass fat and lean percentage, respectively. These responses were consistent with the moderately to highly, favourable genetic correlations among and between performance and carcass composition traits. Genetic changes in growth rate, ultrasonic backfat, food conversion ratio, carcass daily gain, carcass fat and lean percentage when measured on ad libitum individual feeding were all economically beneficial. The high growth line had a significantly lower voluntary daily food intake and residual food intake than the contemporaneous low line, indicating a reduced energy requirement for maintenance in the high relative to the low line. Genetic correlations between either growth rate or backfat and carcass traits were favourable but unfavourable between daily food intake and carcass fat or lean percentage, implying that selection strategies which place emphasis on increased leanness and decreased fatness would result in a decline in voluntary food intake of the animals. The descendants of breeding pigs selected for high post-weaning daily gain on restricted feeding showed significantly increased growth rates, slaughter weights and carcase lean percentages and reduced fatness when grown in group housing with ad libitum feeding. This suggests that restricted feeding is an effective performance testing approach for seedstock lines supplying commercial regimens with group housing and ad libitum feeding. Carcase lean pH values measured 24 hours post-mortem (pH24) were not statistically different between the selected lines, suggesting that an increase in basal metabolic rate due to increased rate of lean deposition in the high relative to the low line may have been compensated for by a reduction in heat production from other sources such as physical activity. Such a reduction was evidenced by a lower residual food intake in the high than the low growth lines. This supports the hypothesis that selection for high growth rate on restricted feeding does not have detrimental effects on pork quality. The sows of the high growth line produced more piglets with significantly heavier weights at birth, giving a potential for better post-natal growth and higher yield of pork weaned per sow per year than the low growth sows. Body weights of the high line sows prior to mating were also significantly higher than those of low line sows suggesting earlier age of sexual maturity. A non-significant tendency for high line sows to have a lower voluntary food intake than low line sows pointed to the possibility that their lower maintenance requirement as growers was carried over to the lactational phase of life. It is concluded that selection for high growth rate on a restricted ration of fixed amount will produce pig strains with a high genetic potential for lean growth, reduced energy requirement for maintenance and improved reproductive performance, and which will be suitable for growing under a wide range of commercial feeding environments.

Responses in growth rate, food conversion efficiency, carcass composition, residual food intake, meat quality and reproduction traits to selection in pigs for four years, for high or low post-weaning growth rate on a fixed but restricted ration were measured in progeny grown on either restricted, ad libitum individual or ad libitum group feeding regimens. Genetic and phenotypic correlations among the traits were also examined on animals whose full pedigrees comprised a total of 5324 animals. Substantial divergent response was achieved from selection for high vs. low growth rate on restricted feeding, with the genetic means of daily gain diverging by 81.25 g or 2.78 genetic standard deviations (SigmaG). The high and low growth rate lines also differed in ultrasonic backfat and food conversion efficiency by 1.12 SigmaG and 0.84 SigmaG, and by 0.88 SigmaG, 1.10 SigmaG, and 1.14 SigmaG for carcass weight daily gain, carcass fat and lean percentage, respectively. These responses were consistent with the moderately to highly, favourable genetic correlations among and between performance and carcass composition traits. Genetic changes in growth rate, ultrasonic backfat, food conversion ratio, carcass daily gain, carcass fat and lean percentage when measured on ad libitum individual feeding were all economically beneficial. The high growth line had a significantly lower voluntary daily food intake and residual food intake than the contemporaneous low line, indicating a reduced energy requirement for maintenance in the high relative to the low line. Genetic correlations between either growth rate or backfat and carcass traits were favourable but unfavourable between daily food intake and carcass fat or lean percentage, implying that selection strategies which place emphasis on increased leanness and decreased fatness would result in a decline in voluntary food intake of the animals. The descendants of breeding pigs selected for high post-weaning daily gain on restricted feeding showed significantly increased growth rates, slaughter weights and carcase lean percentages and reduced fatness when grown in group housing with ad libitum feeding. This suggests that restricted feeding is an effective performance testing approach for seedstock lines supplying commercial regimens with group housing and ad libitum feeding. Carcase lean pH values measured 24 hours post-mortem (pH24) were not statistically different between the selected lines, suggesting that an increase in basal metabolic rate due to increased rate of lean deposition in the high relative to the low line may have been compensated for by a reduction in heat production from other sources such as physical activity. Such a reduction was evidenced by a lower residual food intake in the high than the low growth lines. This supports the hypothesis that selection for high growth rate on restricted feeding does not have detrimental effects on pork quality. The sows of the high growth line produced more piglets with significantly heavier weights at birth, giving a potential for better post-natal growth and higher yield of pork weaned per sow per year than the low growth sows. Body weights of the high line sows prior to mating were also significantly higher than those of low line sows suggesting earlier age of sexual maturity. A non-significant tendency for high line sows to have a lower voluntary food intake than low line sows pointed to the possibility that their lower maintenance requirement as growers was carried over to the lactational phase of life. It is concluded that selection for high growth rate on a restricted ration of fixed amount will produce pig strains with a high genetic potential for lean growth, reduced energy requirement for maintenance and improved reproductive performance, and which will be suitable for growing under a wide range of commercial feeding environments.

Nosso grupo de pesquisa estuda ritmos circadianos em um roedor subterrâneo do gênero Ctenomys, o tuco-tuco. Nesta tese, apresentarei dados sobre sincronização fótica e não-fótica dos ritmos circadianos em tuco-tucos, e sobre sincronização não-fótica em camundongos. Investigamos a sincronização fótica em tuco-tucos por meio de uma abordagem conjunta de campo e laboratório. Inicialmente medimos o ciclo claro/escuro natural percebido por animais mantidos em áreas cercadas em campo, utilizando aparelhos light loggers que registraram continuamente o padrão temporal diário da exposição à luz. Em seguida, foi aplicado um modelo desse padrão de exposição à luz em laboratório, para testar o seu potencial como um sincronizador fótico dos ritmos circadianos dos tuco-tucos. O modelo consistiu em pulsos de luz aplicados uma vez por dia em diferentes momentos aleatórios. Apesar de carregar o mínimo de informação temporal, esse regime luminoso foi um sincronizador eficiente em muitos casos, tal como previsto anteriormente a partir de simulações computacionais de um oscilador matemático. Os resultados revelam que a sincronização de osciladores circadianos é ainda mais robusta do que se imaginava. Nosso segundo conjunto de experimentos avaliou a sincronização não-fótica em tuco-tucos, os quais são herbívoros, expostos a ciclos diários de disponibilidade de alimentos. Semelhante a outras espécies de roedores, tuco-tucos desenvolveram uma atividade antecipatória ao alimento, expressa diariamente antes da alimentação. Houve, no entanto, grande variabilidade inter-individual na expressão da atividade antecipatória, provavelmente relacionada com diferenças nas respostas metabólicas à restrição temporal do alimento. O trabalho final foi uma colaboração com o Dr. Shin Yamazaki, sobre sincronização não-fótica em camundongos do tipo selvagem e camundongos mutantes com ablação genética do relógio circadiano. Ciclos diários de alimentos palatáveis e de corrida em roda induziram ritmicidade autossustentada em camundongos mutantes arrítmicos, que não expressavam os genes Period, componentes importantes da maquinaria molecular que gera os ritmos circadianos nas células. Estes resultados sugerem a existência de novos osciladores circadianos que respondem a sinais diários de recompensa. Enquanto espécies modelo de laboratório, tais como o camundongo, podem trazer informações valiosas sobre os mecanismos fisiológicos, as espécies selvagens como o tuco-tuco podem nos dar pistas sobre o significado ecológico dos fenômenos circadianos / Our research group studies circadian rhythms in a subterranean rodent from the genus Ctenomys, the tuco-tuco. In this thesis, I will present data on photic and non-photic synchronization of circadian rhythms in tuco-tucos, as well as a study on non-photic synchronization in the laboratory mouse. Natural photic synchronization in tuco-tucos was verified with field and laboratory approaches. We initially measured the natural light/dark cycle experienced by tuco-tucos in semi natural field enclosures, by means of automatic light logger devices that continuously recorded the daily temporal pattern of light exposure. Next, a model of this light exposure pattern was applied to tuco-tucos in the laboratory, to test its potential as a photic synchronizer of the circadian rhythms. The model consisted of single light pulses applied once a day at varying random times. Despite the minimal timing information, this light regimen was a successful synchronizer in many instances, as predicted from previous computer simulations of a mathematical oscillator. These results revealed that the synchronization of circadian oscillators is even more robust than previously thought. Our second set of experiments evaluated the non-photic synchronization in the herbivorous tuco-tucos, by exposing animals to daily cycles of food availability. Similar to other rodent species, tuco-tucos in this protocol developed a circadian food anticipatory activity (FAA) right before the daily feeding time. However, there was great interindividual variability in FAA expression, likely related to differences in the metabolic responses to time-restricted feeding. The final work was a collaboration with Dr. Shin Yamazaki from the University of Texas Southwestern Medical Center, regarding non-photic synchronization in wildtype and mutant mice with genetic disruption of the circadian clock. Daily cycles of palatable food and wheel running induced self-sustaining rhythmicity in arrhythmic mutant mice, which do not express the Period genes, key components of the molecular machinery responsible for circadian rhythm generation within the cells. These results suggest the existence of novel circadian oscillators responsive to daily rewarding signals. While model laboratory species such as the mouse can bring valuable information on physiological mechanisms, wild species like the tuco-tuco can give us insights into the ecological meaning of circadian phenomena

This research project consisted of five experiments. The main objective of this study was to determine the effects of restricted feeding and season on growth, carcass characteristics, meat chemical composition, reproduction and egg laying performance of Koekoek chickens. Feed restriction lowered the body weight, weight gain, feed intake and improved the feed conversion efficiency during the rearing phase. During the laying phase, chickens that were in the RA treatment had higher body weights, weight gains and lower FCR. Chickens that were reared in summer had a higher body weight, weight gain and FCR, while total feed intake and mortality rates were high in winter. Feed restriction reduced the slaughter weight, defeathered weight, dressed weight, skin weight, breast muscle weight, shank width, chest width and heart girth during the rearing phase. The intestine, liver and abdominal fat pad weights were higher in chickens that were fed ad libitum. Chickens that were reared in summer had higher shank width, slaughter weight, defeathered weight, chest width, heart girth, breast muscle weight, skin weight, abdominal fat pad weight, intestine weight, liver weight and the relative skin percentage at the age of 18 weeks. During the laying phase, abdominal fat pad weight, abdominal fat pad percentage, intestine percentage, liver weight, gizzard weight and gizzard percentage were higher in the ad libitum fed chickens. Unrestricted feeding during the rearing phase increased the development of combs, wattles, pubic bones, ovaries and oviducts more than restricted feeding while at the age of 32 weeks, enhanced growth of the reproductive organs was seen in chickens that were fed ad libitum only during the laying phase (RA). The cold winter conditions hindered the growth of the combs, wattles, pubic bones, oviducts and ovaries. Restricted feeding during the laying phase reduced the laying percentage, egg weights and improved the hatching percentage. Ad libitum feeding during the rearing phase resulted in the attainment of puberty at an earlier age in chickens. Chickens that were produced in summer reached puberty first as well as 20%, 50% and 80% egg production, and had a higher average laying percentage and egg weights. / Thesis (PhD)--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted