1,720,960 research outputs found
Protein oxidation in non-exercising healthy adults under varying dietary conditions: Physiological determinants, effects on fuel partitioning, and implications for body weight regulation
No full textBackground: Protein oxidation (PROTOX) typically accounts for the smallest fraction of daily energy expenditure (24hEE) in humans compared to carbohydrate and lipid oxidation. However, inter-individual differences in PROTOX may explain differences in fuel partitioning and body weight change. We aimed to elucidate the physiological determinants of PROTOX under controlled 24-h dietary conditions, including eucaloric feeding, fasting, and overfeeding diets with variable protein content. Methods: Eighty-six weight-stable healthy volunteers with normal glucose regulation (67 M/19F; age: 37 ± 10 years; BMI: 26.7 ± 4.5 kg/m2, body fat by DXA: 29.0 ± 9.8 %) underwent 24hEE measurements by whole-room calorimetry during energy balance (20 % protein, 50 % carbohydrate), different overfeeding diets (200 % of the daily eucaloric requirement), including three normal-protein (20 %) diets (balanced: 50 % carbohydrate; high-carbohydrate: 75 % carbohydrate; high-fat: 60 % fat), low-protein (3 %) and high-protein (30 %), and 24-h fasting in a randomized crossover design. Urine samples were collected during each 24-h dietary intervention for quantification of PROTOX and catecholamine excretion rates by nitrogen excretion and high-performance liquid chromatography, respectively. Results: PROTOX during energy balance (mean ± SD: 372 ± 78 kcal/day) was positively associated with protein intake (r = 0.39, p < 0.001), fat free mass (r = 0.35, p < 0.001), but not with fat mass (p = 0.24). Higher PROTOX was associated with higher 24-h urinary norepinephrine (partial r = 0.27, p = 0.01), but not epinephrine (p = 0.48), excretion rates. During normal-protein diets, higher PROTOX was associated with lower lipid oxidation, but not carbohydrate oxidation. Inter-individual variability in PROTOX did not predict changes in weight or body composition over two years. Conclusion: Dietary protein content, lean body mass, and sympathetic nervous system activity are key determinants of PROTOX. Although PROTOX did not predict free-living weight gain, increased PROTOX is associated with decreased lipid oxidation, underscoring its role in fuel partitioning and whole-body energy and substrate balance
Effects of Short-Term Fasting on Ghrelin/GH/IGF-1 Axis in Healthy Humans: the Role of Ghrelin in the Thrifty Phenotype
No full textA greater decrease in 24-hour energy expenditure (24hEE) during short-term fasting is indicative of a thrifty phenotype. As ghrelin and the growth hormone (GH) - insulin-like growth factor 1 (IGF-1) axis are implicated in the regulation of energy intake and metabolism, we investigated whether ghrelin, GH and IGF-1 concentrations mediate the fasting-induced decrease in 24hEE that characterizes thriftiness
The association between gut hormones and diet‐induced metabolic flexibility in metabolically healthy adults
No full textObjective
This study investigated whether interindividual variance in diet-induced metabolic flexibility is explained by differences in gut hormone concentrations.
Methods
A total of 69 healthy volunteers with normal glucose regulation underwent 24-hour assessments of respiratory quotient (RQ) in a whole-room indirect calorimeter during eucaloric feeding (EBL; 50% carbohydrate, 30% fat) and then, in a crossover design, during 24-hour fasting and three normal-protein (20%) overfeeding diets (200% energy requirements). Metabolic flexibility was defined as the change in 24-hour RQ from EBL during standard (50% carbohydrate), high-fat (60%), and high-carbohydrate (75%) overfeeding diets. Plasma concentrations of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) after an overnight fast were measured prior to and after each diet.
Results
Compared with EBL, on average, 24-hour RQ decreased by ~4% during high-fat overfeeding, whereas it increased by ~4% during standard overfeeding and by ~9% during high-carbohydrate overfeeding. During high-carbohydrate overfeeding, but not during any other overfeeding diet or fasting, increased GLP-1 concentration was associated with increased RQ (r = 0.44, p < 0.001), higher/lower carbohydrate/lipid oxidation rates (r = 0.34 and r = −0.51, both p < 0.01), respectively, and increased plasma insulin concentration (r = 0.38, p = 0.02).
Conclusions
Increased GLP-1 concentration following high-carbohydrate overfeeding associated with a greater shift to carbohydrate oxidation, suggesting that GLP-1 may be implicated in diet-induced metabolic flexibility to carbohydrate overload
Impaired metabolic flexibility to fasting is associated with increased ad libitum energy intake in healthy adults
No full textObjective: We investigated how changes in 24-h respiratory exchange ratio (RER) and substrate oxidation during fasting versus an energy balance condition influence subsequent ad libitum food intake. Methods: Forty-four healthy, weight-stable volunteers (30 male and 14 female; mean [SD], age 39.3 [11.0] years; BMI 31.7 [8.3] kg/m2) underwent 24-h energy expenditure measurements in a respiratory chamber during energy balance (50% carbohydrate, 30% fat, and 20% protein) and 24-h fasting. Immediately after each chamber stay, participants were allowed 24-h ad libitum food intake from computerized vending machines. Results: Twenty-four-hour RER decreased by 9.4% (95% CI: -10.4% to -8.5%; p < 0.0001) during fasting compared to energy balance, reflecting a decrease in carbohydrate oxidation (mean [SD], -2.6 [0.8] MJ/day; p < 0.0001) and an increase in lipid oxidation (2.3 [0.9] MJ/day; p < 0.0001). Changes in 24-h RER and carbohydrate oxidation in response to fasting were correlated with the subsequent energy intake such that smaller decreases in fasting 24-h RER and carbohydrate oxidation, but not lipid oxidation, were associated with greater energy intake after fasting (r = 0.31, p = 0.04; r = 0.40, p = 0.007; and r = -0.27, p = 0.07, respectively). Conclusions: Impaired metabolic flexibility to fasting, reflected by an inability to transition away from carbohydrate oxidation, is linked with increased energy intake
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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