James A Betts

James A Betts
University of Bath | UB · Department for Health

About

158
Publications
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Publications

Publications (158)
Preprint
Background: The role of nutrient timing in energy intake amongst people with dysglycaemia is understudied but could be a simple method to help regulate appetite. This study analysed within-person associations of sugar intake at breakfast and subsequent energy intake. Methods: We used 4-day diet diary data from 147 participants (47 % men) encompassi...
Poster
Full-text available
PURPOSE: Establish the time-course of changes in oxygen consumption, substrate metabolism, and heart rate during treadmill walking upon commencing a low-carbohydrate, ketogenic diet. METHODS: In a randomized, parallel group design, 53 healthy men and women (mean±SD, age: 35±16 years, body mass index: 24±3 kg/m2) were allocated to either a moderate...
Article
Introduction: Continuous exercise can increase postprandial gut hormone such as glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) responses but it is unknown whether interrupting prolonged sitting with intermittent walking elicits this effect. Method: Ten participants with central overweight/obesity (7 men and 3 postmenopausal women, 51 ± 5 y...
Article
Caffeine is a psycho-active stimulant that can improve physical and cognitive performance. We systematically reviewed the evidence on the effects of acute caffeine ingestion on physiological parameters, physical and technical-skill performance during high-performance team-sport match-play. Following PRISMA guidelines, studies were identified using...
Article
Full-text available
Daily (circadian) rhythms coordinate our physiology and behaviour with regular environmental changes. Molecular clocks in peripheral tissues (e.g. liver, skeletal muscle, and adipose) give rise to rhythms in macronutrient metabolism, appetite regulation and the components of energy balance - such that our bodies can align the periodic delivery of n...
Article
It is unclear whether neuromuscular electrical stimulation (NMES) has meaningful metabolic effects when users have the opportunity to self-select the intensity to one that can be comfortably tolerated. Nine healthy men aged 28 ± 9 y (mean ± SD) with a body mass index 22.3 ± 2.3 kg/m ² completed 3 trials involving a 2-h oral glucose tolerance test w...
Article
A high dose of whey protein hydrolysate fed with milk minerals rich in calcium (Capolac ® ) results in enhanced glucagon-like peptide-1 (GLP-1) concentrations in lean individuals, however the effect of different calcium doses ingested alongside protein is unknown. The present study assessed the dose response of calcium fed alongside 25 g whey prote...
Article
Purpose of review: To consider emerging research into the physiological effects of excessive dietary carbohydrate intake, with a particular focus on interactions with physical activity. Recent findings: A single episode of massive carbohydrate overload initiates physiological responses to stimulate additional peptide hormone secretion by the gut...
Article
Full-text available
This study investigated whether carbohydrate-energy replacement immediately after prolonged endurance exercise attenuates insulin sensitivity the following morning, and whether exercise improves insulin sensitivity the following morning independent of an exercise-induced carbohydrate deficit. Oral glucose tolerance and whole-body insulin sensitivit...
Article
Constant routine and forced desynchrony protocols typically remove the effects of behavioural/environmental cues to examine endogenous circadian rhythms, yet this may not reflect rhythms of appetite regulation in the real world. It is therefore important to understand these rhythms within the same subjects under controlled diurnal conditions of lig...
Article
New findings: What is the central question of this study? To explore the relationship between proteins in skeletal muscle and adipose tissue determined at rest and peak rates of fat oxidation in men and women. What is the main finding and its importance? Resting content of proteins in skeletal muscle involved in triglyceride hydrolysis and mitocho...
Article
Full-text available
This study assessed the effects of glucose-fructose co-ingestion during recovery from high-intensity rugby training on subsequent performance. Nine professional, senior academy Rugby Union players performed two trials in a double-blind, randomized, crossover design. Identical rugby training sessions were separated by a 3-hour recovery period, durin...
Article
Full-text available
Purpose Intermittent energy restriction commonly refers to ad libitum energy intake punctuated with 24 h periods of severe energy restriction. This can improve markers of metabolic health but the effects on bone metabolism are unknown. This study assessed how 24 h severe energy restriction and subsequent refeeding affected markers of bone turnover....
Article
Full-text available
PRESENT 2020: Texto que desarrolla la lista de verificación para el adecuado informe de la evidencia en ensayos clínicos de deporte y nutrición del ejercicio (Traducción Inglés-Español)
Article
Full-text available
PurposeTo examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training.Methods In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30–60 min at 70–75% maximal oxygen uptake (VO2max) 4 times/week. Participant...
Article
Full-text available
Objective: An important notion in personalized medicine is that there is clinically relevant treatment response heterogeneity. Low-carbohydrate (CHO) and low-fat diets are widely adopted to reduce body mass. To compare individual differences in responses between two dietary interventions, a formal statistical comparison of response variances betwe...
Article
Full-text available
Purpose To examine whether calcium type and co-ingestion with protein alter gut hormone availability. Methods Healthy adults aged 26 ± 7 years (mean ± SD) completed three randomized, double-blind, crossover studies. In all studies, arterialized blood was sampled postprandially over 120 min to determine GLP-1, GIP and PYY responses, alongside appet...
Article
Full-text available
Aim Fibroblast growth factor 21 (FGF21) has recently been implicated in thirst in rodent models. The mechanisms for this are currently uncertain, and it is unclear whether hydration status can alter FGF21 concentrations, potentially providing an additional mechanism by which hypohydration induces thirst. The aim of this study is therefore to unders...
Article
Full-text available
PurposePrior studies exploring the reliability of peak fat oxidation (PFO) and the intensity that elicits PFO (FATMAX) are often limited by small samples. This study characterised the reliability of PFO and FATMAX in a large cohort of healthy men and women.Methods Ninety-nine adults [49 women; age: 35 (11) years; \(\dot{V}\)O2peak: 42.2 (10.3) mL·k...
Article
Full-text available
The analysis of time series data is common in nutrition and metabolism research for quantifying the physiological responses to various stimuli. The reduction of many data from a time series into a summary statistic(s) can help quantify and communicate the overall response in a more straightforward way and in line with a specific hypothesis. Neverth...
Article
Poor postprandial glucose control is a risk factor for multiple health conditions. The second-meal effect refers to the progressively improved glycaemic control with repeated feedings, an effect which is achievable with protein ingestion at the initial eating occasion. The most pronounced glycaemic response each day therefore typically occurs follo...
Article
Purpose: Ingested ethanol (EtOH) is metabolized gastrically and hepatically, which may influence resting and exercise metabolism. Previous exercise studies have provided EtOH intravenously rather than orally, altering the metabolic effects of EtOH. No studies to date have investigated the effects of EtOH ingestion on systemic and peripheral (e.g....
Article
Morning coffee is a common remedy following disrupted sleep yet each factor can independently impair glucose tolerance and insulin sensitivity in healthy adults. Remarkably, the combined effects of sleep fragmentation and coffee on glucose control upon waking per se have never been investigated. In a randomised cross-over design, 29 adults (Mean ±...
Article
Full-text available
Background: Fructose ingestion with a high-fat beverage increases postprandial lipemia when compared with glucose. It is unknown whether other sugars, such as galactose, also increase postprandial lipemia. Objectives: The objective was to assess whether galactose ingestion within a high-fat beverage increases postprandial lipemia relative to glu...
Article
This study investigated metabolic, endocrine, appetite, and mood responses to a maximal eating occasion in fourteen men (mean ±SD: age 28 ±5 y, body mass 77.2 ±6.6 kg, body mass index 24.2 ±2.2 kg·m ⁻² ) who completed two trials in a randomised crossover design. On each occasion participants ate a homogenous mixed-macronutrient meal (pizza). On one...
Article
The timing of carbohydrate ingestion and how this influences net muscle glycogen utilization and fatigue has only been investigated in prolonged cycling. Past findings may not translate to running because each exercise mode is distinct both in the metabolic response to carbohydrate ingestion and in the practicalities of carbohydrate ingestion. To t...
Article
Full-text available
PRESENT 2020: Texto que desarrolla la lista de verificación para el adecuado informe de la evidencia en ensayos clínicos de deporte y nutrición del ejercicio (Traducción Inglés-Español)
Article
Full-text available
Objective: This study investigated the effect of 3 weeks of high-sugar ("Sweet") versus low-sugar ("Plain") breakfast on energy balance, metabolic health, and appetite. Methods: A total of 29 healthy adults (22 women) completed this randomized crossover study. Participants had pre- and postintervention appetite, health, and body mass outcomes me...
Article
Purpose: Maximizing carbohydrate availability is important for many endurance events. Combining pectin and sodium alginate with ingested maltodextrin-fructose (MAL+FRU+PEC+ALG) has been suggested to enhance carbohydrate delivery via hydrogel formation but the influence on exogenous carbohydrate oxidation remains unknown. The primary aim of this st...
Article
Some readers may not have access to the full paper, so a properly formatted and well-written abstract is imperative. Authors should give priority to information about the current study rather than using the abstract for an extensive background or rationale. 2a Methods: Key information regarding the study design, methods, and population should be su...
Article
This study explored lifestyle and biological determinants of peak fat oxidation (PFO) during cycle ergometry, using duplicate measures to account for day-to-day variation. Seventy-three healthy adults (age range: 19–63 years; peak oxygen consumption ; n = 32 women]) completed trials 7–28 days apart that assessed resting metabolic rate, a resting ve...
Article
During short-term recovery, postexercise glucose–fructose coingestion can accelerate total glycogen repletion and augment recovery of running capacity. It is unknown if this advantage translates to cycling, or to a longer (e.g., overnight) recovery. Using two experiments, the present research investigated if postexercise glucose–fructose coingestio...
Article
Full-text available
Context Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness. Objective To assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization, and postprandial glucose metabolism. Design 1) Acute, r...
Article
Background: Few studies have investigated the effect of hydration status on appetite for food in healthy adults. Prior work suggests hydration status does not alter appetite or energy intake, with mixed findings regarding appetite hormone secretion. However, an extensive investigation into both the psychological and physiological appetitive respon...
Preprint
Full-text available
Context Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness. We hypothesised that in men with overweight/obesity, acute exercise before versus after nutrient ingestion would increase whole-body and intramuscular lipid utilization, translating into greater increases in oral gl...
Article
Exploring individual responses to exercise training is a growing area of interest. Understanding reasons behind true observed inter-individual responses may help personalise exercise training to maximise the benefits received. While numerous factors have been explored, an often underappreciated consideration in the sport and exercise science field...
Article
We explore the novel hypothesis that carbohydrate availability is involved in the regulation of energy balance with exercise, via hormonal and neural signals. We propose that carbohydrate availability could play a direct mechanistic role and partially explain previously-documented relationships between a more active lifestyle and tighter control of...
Article
Obesity remains a major public health concern and intermittent fasting is a popular strategy for weight loss, which may present independent health benefits. However, the number of diet books advising how fasting can be incorporated into our daily lives is several orders of magnitude greater than the number of trials examining whether fasting should...
Article
Full-text available
Background: At rest, omission of breakfast lowers daily energy intake, but also lowers energy expenditure, attenuating any effect on energy balance. The effect of breakfast omission on energy balance when exercise is prescribed is unclear. Objectives: The aim of this study was to assess the effect on 24-h energy balance of omitting compared with...
Article
Full-text available
Objective The aim of this study was to determine the effects of sustained morning fasting or breakfast consumption on metabolism, energy intake, and appetite in healthy adults with obesity. Methods An independent‐measures randomized controlled trial with baseline and follow‐up laboratory assessment days separated by a 6‐week intervention of either...
Article
Dietary sugars, exercise and hepatic carbohydrate metabolism – CORRIGENDUM - Javier T Gonzalez, James A Betts
Article
Full-text available
Vitamin D is lipophilic and accumulates substantially in adipose tissue. Even without supplementation, the amount of vitamin D in the adipose of a typical adult is equivalent to several months of the daily reference nutrient intake (RNI). Paradoxically, despite the large amounts of vitamin D located in adipose tissue, individuals with obesity are o...
Article
The aim of this study was to investigate the acute effect of hydration status on glycemic regulation in healthy adults and explore underlying mechanisms. In this randomized crossover trial, 16 healthy adults (8 male) underwent an oral glucose tolerance test (OGTT) when hypohydrated and rehydrated, after four days of pre-trial standardization. One d...
Article
Full-text available
Purpose: Prolonged sitting is a major health concern, targeted via government policy and the proliferation of height-adjustable workstations and wearable technologies to encourage standing. Such interventions have the potential to influence energy balance and thus facilitate effective management of body/fat mass. It is therefore remarkable that th...
Article
The present paper reviews the physiological responses of human liver carbohydrate metabolism to physical activity and ingestion of dietary sugars. The liver represents a central link in human carbohydrate metabolism and a mechanistic crux point for the effects of dietary sugars on athletic performance and metabolic health. As a corollary, knowledge...
Article
Aims: To characterize postprandial glucose flux after exercise in the fed versus overnight fasted-state and to investigate potential underlying mechanisms. Methods: In a randomized order, twelve men underwent breakfast-rest (BR; 3 h semi-recumbent), breakfast-exercise (BE; 2 h semi-recumbent before 60-min of cycling (50% peak power output) and o...
Article
New findings: What is the central question of this study? Glucagon-like peptide-1 (GLP-1) is an important obesity/diabetes target, with effects dependent on circulating GLP-1 concentrations. Peripheral tissues extract GLP-1, therefore sampling venous versus arterialised blood may provide different GLP-1 concentrations. This study examined whether...
Article
The maximal capacity to utilise fat (peak fat oxidation [PFO]) may have implications for health and ultra-endurance performance, and is commonly determined by incremental exercise tests employing 3-minute stages. However, 3-minute stages may be insufficient to attain steady-state gas kinetics, compromising test validity. We assessed whether 4-minut...
Article
Full-text available
Circadian regulation of transcriptional processes has a broad impact on cell metabolism. Here, we compared the diurnal transcriptome of human skeletal muscle conducted on serial muscle biopsies in vivo with profiles of human skeletal myotubes synchronized in vitro. More extensive rhythmic transcription was observed in human skeletal muscle compared...
Data
List of 9211 genes identified by RNA-seq analysis in human skeletal muscle. Rhythmic transcripts (5748) were grouped into genes rhythmic at the pre-mRNA and mRNA level (R-I, R-E), at the pre-mRNA level only (R-I), and at the mRNA level only (R-E).
Data
GO term enrichment analysis for transcripts identified as rhythmic in human skeletal muscle.
Data
Reactome enrichment analysis, using the Panther classification system, for genes that were grouped into model 1. Related to Figure 4—figure supplements 1–3 and Supplementary file 1-table S5.
Data
Detailed list of exact p-values and raw data related to Figures 2 and 3.
Data
Reactome pathway analysis, using the Panther classification system for transcripts that were down- and/or upregulated upon clock disruption. Related to Supplementary file 1-table S5.
Data
List of genes found in each of the 16 models identified by rhythmic analysis of the RNA-seq data. A gene was classified into one category if the probability was >0.5. If the probability was <0.5, transcripts were grouped into model 16 (non-rhythmic). Related to Figure 4—figure supplement 1, Supplementary file 1-tables S4-S6.
Data
This dataset contains the log2 RPKM values for all 25 time points (0 to 48 hr) and the mean of all time points per donor and per condition (siControl/siCLOCK) as well as the model where each gene is grouped.
Data
GO term enrichment analysis, using the Panther classification system, for transcripts that were down- and/or upregulated upon clock disruption. Related to Supplementary file 1-table S4.
Data
List of 190 genes, rhythmic in hSKMs. Transcripts representing non-protein coding sequences, pseudogenes or retired loci are colored in red, transcripts associated with cell cycle are colored in blue, transcripts related to cell differentiation, adhesion and proliferation are colored in green.
Data
List of 16,776 genes identified in hSKM by RNA-seq and used for the differential analysis. Related to Supplementary file 1-tables S2-8.
Data
GO term enrichment analysis, using the Panther classification system, for transcripts that were grouped into model 1. Related to Figure 4—figure supplements 1–3 and Supplementary file 1-table S4.
Article
Purpose: Breaking prolonged sitting reduces postprandial glucose and insulin concentrations and influences skeletal muscle molecular signaling pathways, but it is unknown whether breaking sitting also affects adipose tissue. Methods: Eleven central overweight participants (seven men and four postmenopausal women) 50 ± 5 yr old (mean ± SD) comple...
Article
Full-text available
Background: Short-term overfeeding combined with reduced physical activity impairs metabolic function and alters the expression of key genes within adipose tissue. We have shown that daily vigorous-intensity running can prevent these changes independent of any net effect on energy imbalance. However, which type, intensity and/or duration of exerci...
Article
The initial metabolism of fructose is thought to primarily take place in the liver. Using stable isotope labeling combined with tissue and arterio-venous sampling, Jang et al. (2018) demonstrate that in mice, the small intestine is the primary site of fructose metabolism. This raises important questions about fructose handling in humans. The initia...