Browsing by Author "Melby, Chris, advisor"
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Item Open Access A high energy flux state attenuates the weight loss-induced energy gap by acutely decreasing hunger and increasing satiety and resting metabolic rate(Colorado State University. Libraries, 2014) Foright, Rebecca, author; Melby, Chris, advisor; Davalos, Deana, committee member; Wdowik, Melissa, committee memberIntroduction: Maintaining weight loss is one of the greatest challenges facing obese dieters. Weight loss-induced, compensatory, biological adjustments increase hunger and decrease resting metabolic rate (RMR), resulting in a disconnect between desired and required calories. This phenomenon, termed the energy gap, results in strong biological pressures that promote weight regain. Previous research in athletes has shown that high levels of physical activity coupled with high energy intake may increase RMR and reduce hunger. It is possible that this high energy flux state characterized by high daily energy expenditure (resulting from increased physical activity) with matching high energy intake (high calorie throughput) may attenuate the weight loss-induced energy gap by reducing hunger and increasing RMR. Methods: This proof-of-concept pilot study utilized a within-subjects cross-over experimental design. Six obese adults [age (x±SD: 42±12 y); BMI=35.7±3.7 kg/m2] underwent baseline measures of body weight, body composition, RMR via indirect calorimetry, fasting and post-prandial perceived hunger via visual analog scales, fasting and serial postprandial measures of glucose, insulin, and peptide YY (PYY, an anorexigenic hormone) and ad libitum energy intake from a mid-day food buffet. They then underwent weight loss (7% of initial body weight achieved over several months) and were stabilized at this reduced weight for three weeks. Subjects were then placed in two different 4-day experimental conditions of energy balance in random order--Low Flux (LF): sedentary with energy intake (EI)=RMR x1.35; and HF: daily exercise net energy cost of ~500 kcal/d and EI= RMR x1.7. On each morning of the 4 days of the HF and LF conditions, RMR was measured and hunger and satiety monitored. On the day following the HF and the LF conditions, respectively, participants again underwent measures of RMR, fasting and post-prandial hunger and satiety, fasting and serial postprandial measures of glucose, insulin, and PYY, and ad libitum energy intake from the food buffet. Results: Daily energy intake during HF (x±SD: 3,191±587 kcal/d) was significantly greater (p<0.001) than during LF (x±SD: 2,449±406 kcal/d), but in line with the experimental design, subjects were in energy balance and average weight did not differ between low flux (103±4.8 kg) and high flux (103.4±4.7 kg). Perceived hunger at the end of day was lower (p=0.020), fullness throughout the day was higher (p=0.015) and there was a trend for hunger throughout the day to be lower (p=0.091) in HF compared to LF conditions. Additionally, RMR was significantly higher in HF (1926±138 kcal/day) compared to LF (1847±126 kcal/day; P = 0.05). Fasting and post-prandial glucose concentrations did not significantly change with weight loss. Fasting and postprandial insulin concentrations were lower after weight loss the day following HF and LF compared to pre-weight loss baseline values, but did not differ by flux condition. Fasting PYY concentrations were not different among pre-weight loss, HF, and LF, but postprandial PYY was lower the day following HF compared to pre-weight loss baseline. Ad libitum food intake and subjective feelings of hunger and satiety on the day following HF and LF did not differ between flux conditions or from pre-weight loss baseline values. Conclusions: A 4-day high flux state resulted in decreased hunger, increased satiety and increased RMR in weight-reduced, weight-stable, obese individuals when compared to a low flux state. Our findings support the importance of a daily high energy flux state in attenuating the increase in hunger and the decrease in energy expenditure that accompany diet-induced weight loss. However, the greater satiety and lower hunger were not evident the day following the high flux state, suggesting that such benefits resulting from the acute state are not long-lasting.Item Open Access A one-week controlled diet and exercise intervention significantly improves insulin sensitivity without changes in plasma adiponectin concentrations in young non-Hispanic white and Mexican American adults(Colorado State University. Libraries, 2010) Botero, Maria Fernanda, author; Melby, Chris, advisor; Allen, Kenneth, committee member; Hickey, Matthew, committee memberBackground: Hypoadiponectinemia (low levels of adiponectin in blood) has been linked to insulin resistance and type 2 diabetes (T2D). In the USA, the prevalence of these latter two conditions is higher in Mexican Americans (MA) when compared to Non-Hispanic Whites (NHW). Variations in plasma adiponectin concentrations may partially contribute to differences in insulin resistance and T2D prevalence rates between adults of these two ethnic groups. Also, plasma adiponectin concentrations in MA and NHW adults may respond differently to a diet and exercise intervention. Objectives: 1. To determine whether or not pre-intervention fasting plasma adiponectin concentrations differ between sedentary, non-obese MA and NHW adults; 2. To determine if a combined one-week exercise and diet intervention (controlled low-saturated fat, low-sugar, high-fiber diet) improves both plasma adiponectin concentrations and insulin sensitivity in both NHW and MA adults; 3. To determine if changes in insulin sensitivity are associated with changes in circulating adiponectin concentrations. Methods: During the pre-study phase, volunteers underwent all initial screening tests. Eligible participants [n= 37; (20 NHW; 9 males, 11 females and 17 MA; 4 males, 13 females aged 18-40 years), fasting blood glucose < 126 mg/dl, blood pressure < 140/90 mm Hg, BMI < 30 kg/m2] continued with a 7-day baseline period, in which they were asked to maintain their regular food intake and their usual low level of exercise. A 3-hour intra-venous glucose tolerance test (IVGTT) for the measurement of insulin sensitivity was performed at the end of this period, as well as measurement of fasting plasma adiponectin. The intervention phase started immediately the day after and ended 7 days later. Subjects consumed a diet that was rich in vegetables, fruits, dietary fiber, and lean proteins and low in saturated fat and refined carbohydrates. Study investigators prepared all foods which were provided to participants. Subjects also exercised on a stationary cycle ergometer for 6 out of the 7 days of the intervention (40-45min/session at 65%V02 max). At the end of the intervention, 16-17 hours after the last exercise bout, plasma adiponectin was again measured and another IVGTT was performed. Dependent variables were analyzed using a 2 X 2 repeated measures ANOVA. Results: Insulin action, determined by the 3-h insulin area under the curve (IAUC) in response to glucose infusion, improved significantly (p<0.05) in response to the intervention (IAUC µU*min/L pre, post: MA = 2297, 1635; NHW = 1794, 1210). At baseline, plasma adiponectin levels were not significantly different between NHW and MA adults (NHW= 11.42 mµ/ml, MA= 11.17 mµ/ml) and there were no significant changes in adiponectin in response to the intervention in either group. Conclusion: A one-week diet and exercise intervention significantly improved insulin action in both MA and NHW adults, but changes in circulating adiponectin were not observed. Thus, the improvement in insulin sensitivity in response to a short-term diet/exercise intervention was disassociated from any changes in circulating adiponectin.Item Open Access A single session of sprint interval training increases total daily energy expenditure(Colorado State University. Libraries, 2014) Sevits, Kyle, author; Melby, Chris, advisor; Bell, Christopher, advisor; Gentile, Christopher, committee member; Browning, Ray, committee member; Melanson, Ed, committee memberBackground: Sprint interval training (SIT) is known to elicit favorable physiological adaptations, including improved insulin sensitivity and glucose tolerance. Its utility for weight maintenance is unclear. Presumably any effects would be mediated by increased energy expenditure during both the exercise itself, and during recovery. Therefore, the objective of this study is to determine the effects of a single bout of SIT on 24-hour energy expenditure (EE). Methods: 24-hour EE was determined in 12 healthy men (age: 26 ± 2 years; body mass index: 23.6 ± 0.5 kg/m2; mean ± SE). After three days of controlled diet and maintenance of energy balance, subjects were studied in a whole-room indirect calorimeter for two consecutive days. One of these days (random order) began with a single bout of SIT (5 x 30 second "all-out" exertions on a cycle ergometer against a resistance equivalent to 7.5% body mass, separated by 4 minutes of loadless cycling). Subjects spent the other day in the calorimeter without exercising. Results: An acute bout of SIT increased 24-hour EE in all subjects by an average of 226 ± 15 kcal during an otherwise sedentary day (Control: 2189 ± 58 vs. SIT: 2415 ± 62 kcal/day; P < 0.001). There was also a non-significant (P = 0.054) decrease in fat balance on the exercise day (control = -9.7 ± 7.9 g/day vs. SIT = -20.6 ± 8.2 g/day). Conclusions: Our data provide support for SIT as a time-efficient exercise to increase total daily energy expenditure and may aid in the maintenance of health.Item Open Access Association of pet ownership with eating, exercise, nutritional status, and heart health of seniors(Colorado State University. Libraries, 1995) Dembicki, Diane Florence, author; Anderson, Jennifer, advisor; Melby, Chris, advisor; Stallones, Lorann, committee member; Auld, Garry, committee member; Barber, Clif, committee memberThe familiar adage "pets are good for your health" is an interesting but largely untested theory. Numerous anecdotal remarks on the health benefits of companion animals to the elderly refer to eating and exercise. Research is needed to examine if any health benefits result from pet ownership, and, if so, models must be developed to explain the reasons. An early empirical study found increased survival rate of heart patients due to pets (Freidmann et al., 1980). A theoretical framework is developing based on pet attachment and substitute social support (Stallones et al., 1990). Recent research investigated the effects of pets on risk factors for cardiovascular disease (Anderson et al., 1992). A new model was developed, based on pet ownership leads to better self care, to show possible associations between pet ownership with eating, exercise, nutritional status, and specific cardiovascular risk factors. The major hypotheses tested were pet owners have significantly lower serum total cholesterol, low-density lipoprotein cholesterol, and triglycerides, and higher high-density lipoprotein cholesterol than non-owners and these differences are explained by diet and physical activity. The experimental design was a cross-sectional, observational study of a self-selected convenience sample. Seniors aged sixty and above were solicited at senior congregate meals program sites in north-central Colorado (n=127). Instruments used were questionnaires on eating and exercise, emotional and physical health, social support, and pet attachment, biochemical analyses of diet and blood, and anthropometric and physiological measures. Statistical procedures included two-tailed t-tests, Chi-square, multivariate analysis, correlation coefficients and partial coefficients, and analysis of covariance ; a value of p <0. 05 was considered significant. There were few significant differences in diet, nutritional status, and risk factors for cardiovascular disease and no significant differences in number of exercise activities and duration of walking between pet and nonowners. Dog owners walked significantly longer than nonowners. Pet owners had significantly lower triglycerides than non-owners. It could not be concluded that pet ownership is associated with better diet and nutritional status, greater physical activity, and reduced cardiovascular risk compared to non-ownership in seniors.Item Open Access Cardiometabolic plasticity and skeletal muscle protein expression in Hispanic and non-Hispanic whites in response to a short-term diet and exercise intervention(Colorado State University. Libraries, 2009) Schmidt, Stacy L., author; Melby, Chris, advisor; Hickey, Matt, advisorThe prevalence rates for type 2 diabetes (T2D) and the metabolic syndrome (MetS) have steadily increased to epidemic proportions over the past few decades, with disproportionately high rates of these health problems in Hispanics. The largest minority group in the United States is Hispanics, with Mexican Americans (MA) comprising the largest and fastest growing portion of the US Hispanic population. Insulin resistance is more prevalent in the MA population compared to other ethnic groups, and appears to precede many of the metabolic abnormalities involved in the progression toward T2D and MetS. Insulin resistance and many factors present in the MetS have been shown to improve following an increase in physical activity and consumption of diets low in saturated fatty acids and high in fiber. The overall objective of this project was to determine the combined effects of an increase in exercise combined with dietary lipid and carbohydrate modification on insulin sensitivity and blood lipids, and to determine if differences in expression of skeletal muscle proteins exist in non-obese, non-diabetic sedentary MA and NHW adults.Item Open Access Evaluation of a school-based diabetes education intervention, an extension of Program ENERGY(Colorado State University. Libraries, 2014) Conner, Matthew David, author; Melby, Chris, advisor; Auld, Garry, committee member; Hickey, Matthew S., committee memberBackground: The prevalence of both obesity and type 2 diabetes in the United States has increased over the past two decades nd rates remain high. The latest data from the National Center for Health Statistics estimates that 36% of adults and 17% of children and adolescents in the US are obese (CDC Adult Obesity, CDC Childhood Obesity). Being overweight or obese greatly increases one's risk of developing several chronic diseases, such as type 2 diabetes. Approximately 8% of adults in the US have diabetes, type 2 diabetes accounts for 90-95% of these cases. Type 2 diabetes in children and adolescents is still rare, however clinical reports suggest an increase in the frequency of diagnosis (CDC Diabetes Fact Sheet, 2011). Results from the Diabetes Prevention Program show that the incidence of type 2 diabetes can be reduced through the adoption of a healthier lifestyle among high-risk individuals (DPP, 2002). Objectives: This classroom-based intervention included scientific coverage of energy balance, diabetes, diabetes prevention strategies, and diabetes management. Coverage of diabetes management topics were included in lesson content to further the students' understanding of the disease. Measurable short-term goals of the intervention included increases in: general diabetes knowledge, diabetes management knowledge, and awareness of type 2 diabetes prevention strategies. Methods: A total of 66 sixth grade students at Tavelli Elementary School in Fort Collins, CO completed the intervention. The program consisted of nine classroom-based lessons; students participated in one lesson every two weeks. The lessons were delivered from November of 2005 to May of 2006. Each bi-weekly lesson included a presentation and interactive group activities. Participants completed two diabetes knowledge questionnaires at baseline and post intervention. A diabetes survey developed by Program ENERGY measured general diabetes knowledge and awareness of type 2 diabetes prevention strategies. The second questionnaire, adapted from a survey developed for the Starr County Diabetes Education Study (Garcia et al, 2001), measured general diabetes and diabetes management knowledge. A comparison group, a total of 19 students, also completed both surveys during the study period. Results: Significant increases (p<0.05) were seen in the post-intervention study group in general diabetes knowledge, diabetes management knowledge, and awareness of diabetes prevention strategies, when compared to the baseline study group and comparison group.Item Open Access Multilocus genetic associations with obesity outcomes in Hispanic and non-Hispanic whites using a principal components regression approach: the San Luis Valley Diabetes Study(Colorado State University. Libraries, 2013) Booth-Kalajian, Andrea D., author; Nelson, Tracy, advisor; Melby, Chris, advisor; Hokanson, John, committee member; Peel, Jennifer, committee member; Bellows, Laura, committee memberIntroduction: The overweight and obesity crisis in America has reached alarming rates with little progress of reversing the trend, despite much effort. Heritability has been estimated at up to 70%, though it is still unclear how genetics respond to environmental pressures. Evaluating groups of genes that are known to influence metabolic pathways has given some insight into the variation we see in body composition and prevalence of metabolic diseases. Methods: Data from the San Luis Valley Diabetes Study's third examination were utilized (1997-1998, n=837). One hundred seven single nucleotide polymorphisms (SNP) were selected from 22 genes that have previously been associated with obesity and type 2 diabetes (T2D) in a cohort of Hispanic and non-Hispanic white (NHW) individuals. Genetic data were reduced to a smaller set of derived factors using principal components analysis (PC). Associations were determined between factors and obesity outcomes. Results: Hispanics were more likely to have T2D than NHW (19% vs. 11%). Sample minor allele frequencies for 100 analyzable SNPs varied between the two groups with the minor alleles of rs8059937 (A2BP1) and rs6822807 (UCP1) being significantly more prevalent in Hispanics and rs11724758 (FABP2) and rs2239179 (VDR) significantly more prevalent in NHWs. SNP variance was redistributed into orthogonal components and 32 were retained for analysis, accounting for 77% of the total variance in genetic data. The combined genetic information increased predictive power of increases in body mass index (BMI) from the study baseline by 5.6% in Hispanics. Genetic data increased predictability of BMI and waist circumference (WC) in NHWs by 7.5% and 5.1%, respectively. Both groups had a significant increase in knowledge gained (18%) for the prevalence of T2D when genetic information was added to the base model. SNPs from UCP1 loaded strongly onto PC4, which was associated with BMI change in Hispanics and BMI, WC, and T2D in NHWs. PC7 represented SNPs from RBP4 and FABP2, which was associated with diabetes status in both groups. All obesity outcomes were associated with PC15 in Hispanics, symbolizing SNPs on the PPARD and RBP4 genes. NHWs showed additional associations with components having strong loadings from SNPs on multiple genes, including ADIPOQ, GC, VDR, PPARG, PPARGC1A, PPARD, UCP2, UCP3, and AlOX15. Conclusions: When combined together, multilocus genetic data show a larger influence on obesity outcomes than single polymorphisms alone. Base variations in UCP1, RBP4, and FABP2 gene sequences are associated with change in BMI and diabetes status in Hispanics and BMI, WC, and diabetes status in NHWs.Item Open Access The effects of a single bout of exercise on plasma triglycerides, glucose, and insulin following consumption of a high-fat mixed macronutrient meal(Colorado State University. Libraries, 2011) Smith, Whitney, author; Melby, Chris, advisor; Hickey, Matt, advisor; Nelson, Tracy, committee memberPurpose: The aim of the present study was to examine the effect of a single, acute bout of exercise with caloric replacement compared to a sedentary condition on plasma triglyceride, glucose, and insulin concentrations in response to a high-fat, mixed macronutrient (HFMM) meal challenge. Methods: Eight non-obese, sedentary females aged 19.6 ± 1.3 years participated in two trials: sedentary (SED) and exercise (EX). For the SED trial, subjects refrained from exercise the evening prior to the next morning's HFMM meal. The EX trial was designed to have subjects cycle at 65% of their VO2peak to produce a net energy cost of 400 calories, with a snack provided shortly after to replace the extra calories expended with exercise. However, due to a methodological error, the net energy cost of exercise was less than the targeted value by approximately 100 kcal, which when accompanied by the replacement energy snack, likely resulted in a small acute positive energy balance. Thus, the unintended research question addressed was whether or not a low intensity bout of exercise could attenuate the postprandial lipemic response to a HFMM meal when subjects slightly overcompensated for their exercise energy expenditure. During the trial day subjects reported to the laboratory following a 12-hour overnight fast. Blood samples were obtained by intravenous cannulation before ingestion of the HFMM meal challenge and at 30, 60, 90, 120, 150, 180, 210, 240, 300, and 360 minutes after ingestion. Plasma was analyzed for triglyceride, glucose, and insulin concentrations, with these variables compared across the SED and EX conditions using a repeated measures analysis of variance. Results: There were no significant treatment by time interactions for any of the dependent variables. Low intensity exercise with modest energy overconsumption failed to attenuate the postprandial triglyceride, glucose, and insulin responses to a HFMM meal challenge in comparison to the SED condition. Conclusion: A low intensity exercise bout accompanied by modest energy overconsumption failed to improve the postprandial response to a HFMM meal challenge compared to the HFMM meal challenge without exercise. Exercise alone may not be beneficial in attenuating postprandial lipemia unless it is accompanied by a resulting acute caloric deficit.Item Open Access Using participatory action research methods to create nutrition education that sustainably improves diet diversity through women's empowerment(Colorado State University. Libraries, 2021) Sly, Brittney Catherine, author; Weir, Tiffany, advisor; Melby, Chris, advisor; Cunningham-Sabo, Leslie, committee member; Leisz, Stephen, committee memberMalnutrition is a major cause of morbidity and mortality for vulnerable sub-Saharan African populations, and despite decades-long efforts from global and regional organizations, the prevalence of malnutrition is not improving. Many programs fail to address the underlying causes of malnutrition within specific cultural and community contexts, particularly issues that contribute to malnutrition such as hygiene, agriculture, education, and poverty reduction. Therefore, there is a need for more sustainable, culturally inclusive, and targeted malnutrition remediation interventions that address the multifaceted issues involved with the rising numbers of malnourished people in sub-Saharan Africa. The purpose of this research was to develop a nutrition-sensitive agriculture intervention, aimed at sustainably increasing diet diversity and food security at the household level, in a rural Rwandan community, using Participatory Action Research (PAR) methods to empower women as peer educators. Small groups of women (n=42), divided into 6 groups of 7, collectively received agriculture trainings and nutrition education over the course of 16 weeks, along with the tools and support to start and maintain kitchen gardens. A large group session, using PAR methodology, was conducted to guide self-reflection and knowledge-assessment, while empowering women educators to spread information throughout their community. By coupling the intention of nutrition-sensitive agriculture with the empowering and inclusive methods of PAR, the goal was to provide the framework for establishing more sustainable nutrition-sensitive agriculture interventions, while encouraging the dissemination of information to the larger community. Collaborative community-based nutrition-sensitive agricultural interventions in rural, poor Rwandan populations can increase household diet diversity to encourage sustained change in dietary patterns for nutritional adequacy. Using kitchen gardens as the conduit for change, households can increase their consumption of home-grown vegetables, as well as other nutrient-dense foods. Additionally, employing PAR methods within the intervention design to enable participants to serve as active contributors and peer educators, enhanced women's empowerment and contributed to increased agency, as well as widespread information dissemination. However, more research concerning the systems that affect food availability and agricultural markets is needed to enact changes in food security, as well as more investigation into the ways in which empowerment influences the spread of information throughout a community.