Javier T Gonzalez

Javier T Gonzalez
University of Bath | UB · Department for Health

42.59
 · 
Bsc MRes PhD

About

111
Publications
36,166
Reads
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783
Citations
Research Experience
December 2017 - present
University of Bath
Position
  • Senior Lecturer (Associate Professor)
September 2014 - November 2017
University of Bath
Position
  • Lecturer (Assistant Professor)
September 2010 - present
Northumbria University
Position

Publications

Publications (111)
Article
Carbohydrate and fat are the main substrates utilized during prolonged endurance-type exercise. The relative contribution of each is primarily determined by the intensity and duration of exercise, along with individual training and nutritional status. During moderate-to-high intensity exercise, carbohydrate represents the main substrate source. As...
Article
Full-text available
Carbohydrate availability in the form of muscle and liver glycogen is an important determinant of performance during prolonged bouts of moderate‐ to high‐intensity exercise. Therefore, when effective endurance performance is an objective on multiple occasions within a 24‐h period, the restoration of endogenous glycogen stores is the principal facto...
Article
Purpose: To define the effect of glucose ingestion compared to sucrose ingestion on liver and muscle glycogen depletion during prolonged endurance-type exercise. Methods: Fourteen cyclists completed two 3-h bouts of cycling at 50% of peak power output while ingesting either glucose or sucrose at a rate of 1.7 g/min (102 g/h). Four cyclists perfo...
Article
Full-text available
The present study examined the impact of breakfast and exercise on postprandial metabolism, appetite and macronutrient balance. A sample of twelve (blood variables n 11) physically active males completed four trials in a randomised, crossover design comprising a continued overnight fast followed by: (1) rest without breakfast (FR); (2) exercise wit...
Article
Purpose: To assess the effects of sucrose versus glucose ingestion on post-exercise liver and muscle glycogen repletion. Methods: Fifteen well-trained male cyclists completed 2 test days. Each test day started with glycogen-depleting exercise, followed by 5 h of recovery, during which subjects ingested 1.5 g·kg⁻¹·h⁻¹ sucrose or glucose. Blood wa...
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
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
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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
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
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
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...
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 g...
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
Full-text available
Carbohydrate availability is important to maximize endurance performance during prolonged bouts of moderate‐ to high‐intensity exercise as well as for acute post‐exercise recovery. The primary form of carbohydrates that are typically ingested during and after exercise are glucose (polymers). However, intestinal glucose absorption can be limited by...
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
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Fructose is a commonly‐ingested dietary sugar which has been implicated in playing a particularly harmful role in the development of metabolic disease. Fructose is primarily metabolised by the liver in humans, and increases rates of hepatic de novo lipogenesis. Fructose increases hepatic de novo lipogenesis via numerous mechanisms; by altering tran...
Article
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Academic periodization is based on concepts used to optimize elite sporting performance and this may represent an effective approach to help young academics reflect on their working practices in order to meet the demands of their roles. The focus on maximizing efficiency hopes to benefit performance, but also to reduce the risk of early career acad...
Article
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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
Purpose: To monitor physiological, technical, and performance responses to individualized high-intensity interval training (HIIT) prescribed using the critical speed (CS) and critical stroke rate (CSR) concepts in swimmers completing a reduced training volume program (≤30 km·wk-1) for 15 weeks. Methods: Over the 15-week period, 12 highly trained...
Article
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Background: Prior studies have shown that intermittent fasting is capable of producing improvements in body weight and fasted health markers. However, the extent to which intermittent fasting incurs compensatory changes in the components of energy balance and its impact on postprandial metabolism are yet to be ascertained. Methods: A total of 30...
Article
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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
The objective of this review paper is to evaluate the impact of undertaking aerobic exercise in the overnight-fasted v. fed-state, in the context of optimising the health benefits of regular physical activity. Conducting a single bout of aerobic exercise in the overnight-fasted v. fed-state can differentially modulate the aspects of metabolism and...
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
Purpose: To assess the concurrent and predictive validity of the 3-min all-out test (3MT) against conventional methods (CM) of determining critical speed (CS) and curvature constant (D'), and to examine the test-retest reliability of the 3MT in highly-trained swimmers. Methods: Thirteen highly-trained swimmers (age: 16 ± 2 y, weight: 64.7 ± 8.5...
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...
Article
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The importance of post-exercise recovery nutrition has been well described in recent years, leading to its incorporation as an integral part of training regimes in both athletes and active individuals. Muscle glycogen depletion during an initial prolonged exercise bout is a main factor in the onset of fatigue and so the replenishment of glycogen st...
Article
Full-text available
The carbohydrate deficit induced by exercise is thought to play a key role in increased post-exercise insulin action. However, the effects of replacing carbohydrate utilized during exercise on postprandial glycaemia and insulin sensitivity are yet to be determined. This study therefore isolated the extent to which the insulin-sensitizing effects of...
Article
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Exposure to hypoxia appears to depress appetite and energy intake, however the mechanisms are not fully understood. The aim of this review was to determine the magnitude of changes in hunger and energy intake in hypoxic compared with normoxic environments, and establish any alterations in appetite-related hormone concentrations. PubMed and The Coch...
Article
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Key points: In lean individuals, 6 weeks of extended morning fasting increases the expression of genes involved in lipid turnover (ACADM) and insulin signalling (IRS2) in subcutaneous abdominal adipose tissue. In obese individuals, 6 weeks of extended morning fasting increases IRS2 expression in subcutaneous abdominal adipose tissue. The content a...
Article
The role of dietary carbohydrates in the development of obesity and associated metabolic dysfunction has recently been questioned. Within the last decade, the Scientific Advisory Committee on Nutrition carried out a comprehensive evaluation of the role of dietary carbohydrates in human health. The current review aims to complement and extend this r...
Article
Oral glucose tolerance and insulin sensitivity are common measures, but are determined using various blood sampling methods, employed under many different experimental conditions. This study established whether measures of oral glucose tolerance and oral glucose-derived insulin sensitivity (insulin sensitivity indices; ISI) differ when calculated f...
Article
Following ingestion of a mixed-macronutrient meal, blood glucose and triacylglycerol (TAG) concentrations are elevated for approximately 2 and 8 hours, respectively, depending on factors such as the amount and type of food ingested. For many individuals who consume at least three meals per day, the majority of waking hours are thus spent in a postp...
Article
Aim: To evaluate an additional rapid-acting insulin bolus on postprandial lipaemia, inflammation and pro-coagulation following high-carbohydrate high-fat feeding in people with type 1 diabetes. Methods: A total of 10 males with type 1 diabetes [HbA1c 52.5 ± 5.9 mmol/mol (7.0% ± 0.5%)] underwent three conditions: (1) a low-fat (LF) meal with norm...
Article
Feeding profoundly affects metabolic responses to exercise in various tissues but the effect of feeding status on human adipose tissue responses to exercise has never been studied. Ten healthy overweight men aged 26 ± 5 years (mean ± SD) with a waist circumference of 105 ± 10 cm walked at 60% of maximum oxygen uptake under either FASTED or FED cond...
Article
Personalised nutrition can be defined as developing unique nutrition guidelines for each individual; precision nutrition seeks to develop effective approaches based on the combination of an individual's genetic, environmental and lifestyle factors. The former infers variants that underlie traits are largely fixed (i.e. stable across time) and appea...
Article
Aim: To determine if neuromuscular disturbances are modulated following a repeated bout of eccentric exercise METHODS: Following eccentric exercise performed with the elbow-flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase and voluntary activation using motor point and motor cortex stimulation at...
Article
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Background Muscles get smaller and weaker as we age and become more vulnerable to atrophy when physical activity is reduced or removed. This research is designed to investigate the potentially protective effects of two separate exercise strategies against loss in skeletal muscle function and size, and other key indices of health, following 14 days...
Article
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Individual differences in appetite are increasingly appreciated. However, the individual day-to-day reliability of appetite measurement is currently uncharacterised. This study aimed to assess the reliability of appetite following ingestion of mixed-macronutrient liquid meals at a group- and individual-level. Two experiments were conducted with ide...
Article
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Single-course, ad libitum meals are recommended for the assessment of energy intake within appetite research. This study represents the first investigation of the comparative sensitivity of two single-course, ad libitum meals designed to differ in palatability. We conducted two experiments using a preload study design. All protocols were identical...
Article
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Patients with type 1 diabetes are provided guidance and structured education on adjusting their mealtime bolus insulin dose based on meal carbohydrate content. However, recent research in patients using continuous subcutaneous insulin infusion has highlighted the role of dietary fat in increasing prandial insulin requirements, particularly late int...
Article
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The Bath Breakfast Project is a series of randomised controlled trials exploring the effects of extended morning fasting on energy balance and health. These trials were categorically not designed to answer whether or not breakfast is the most important meal of the day. However, this review will philosophise about the meaning of that question and ab...
Article
Maximal eccentric contractions induce an immediate strength loss that results from skeletal muscle damage, the symptoms of which can persist for several days after the exercise insult. The repeated bout effect (RBE) refers to the acute adaptive response precipitated from a single bout of eccentric contractions that result in an attenuated damage re...
Article
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We aimed to assess postprandial metabolic and appetite responses to a mixed-macronutrient lunch following prior addition of whey protein to a carbohydrate-rich breakfast. Ten healthy males (age: 24 ± 1 years; body mass index (BMI): 24.5 ± 0.7 kg/m²) completed three trials in a non-isocaloric, crossover design. A carbohydrate-rich breakfast (93 g ca...
Article
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Background: Type 1 diabetes is associated with raised inflammation, impaired endothelial progenitor cell mobilisation and increased markers of vascular injury. Both acute and chronic exercise is known to influence these markers in non-diabetic controls, but limited data exists in Type 1 diabetes. We assessed inflammation, vascular repair and injury...
Conference Paper
Full-text available
PURPOSE: Resting pulmonary function (PFT) is known to have important effects on ventilation, gas exchange and breathing mechanics during exercise and consequently, is routinely assessed in athletes. ATS/ERS guidelines recommend that individuals should avoid a large meal 2-hr prior to PFT testing to avoid measurement contraindication. However, for e...
Article
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Evening-time exercise is a frequent cause of severe hypoglycemia in type 1 diabetes, fear of which deters participation in regular exercise. Recommendations for normalizing glycemia around exercise consist of prandial adjustments to bolus insulin therapy and food composition, but this carries only short-lasting protection from hypoglycemia. Therefo...