Exercise and ghrelin. A narrative overview of research

Acute effects of exercise intensity on butyrylcholinesterase and ghrelin in young men: A randomized controlled study

Background/objectives

Butyrylcholinesterase (BChE), a liver-derived enzyme that hydrolyzes acylated ghrelin to des-acylated ghrelin, may trigger a potential mechanism responsible for the acute exercise-induced suppression of acylated ghrelin. However, studies examining the effects of an acute bout of high-intensity exercise on BChE and acylated ghrelin have yielded inconsistent findings. This study aimed to examine the acute effects of exercise intensity on BChE, acylated ghrelin and des-acylated ghrelin concentrations in humans.

Methods

Fifteen young men (aged 22.7 ± 1.8 years, mean ± standard deviation) completed three, half-day laboratory-based trials (i.e., high-intensity exercise, low-intensity exercise and control), in a random order. In the exercise trials, the participants ran for 60 min (from 09:30 to 10:30) at a speed eliciting 70 % (high-intensity) or 40 % (low-intensity) of their maximum oxygen uptake and then rested for 90 min. In the control trial, participants sat on a chair for the entire trial (from 09:30 to 12:00). Venous blood samples were collected at 09:30, 10:00, 10:30, 11:00, 11:30 and 12:00.

Results

The BChE concentration was not altered over time among the three trials. Total acylated and des-acylated ghrelin area under the curve during the first 60 min (i.e., from 0 min to 60 min) of the main trial were lower in the high-intensity exercise trial than in the control (acylated ghrelin, mean difference: 62.6 pg/mL, p < 0.001; des-acylated ghrelin, mean difference: 31.4 pg/mL, p = 0.035) and the low-intensity exercise trial (acylated ghrelin, mean difference: 87.7 pg/mL, p < 0.001; des-acylated ghrelin, mean difference: 43.0 pg/mL, p = 0.042).

Conclusion

The findings suggest that BChE may not be involved in the modulation of ghrelin even though lowered acylated ghrelin concentration was observed after high-intensity exercise.

Physical Exercise and Appetite Regulation: New Insights

Physical exercise is considered an important physiological intervention able to prevent cardiovascular diseases, obesity, and obesity-related cardiometabolic imbalance. Nevertheless, basic molecular mechanisms that govern the metabolic benefits of physical exercise are poorly understood. Recent data unveil new mechanisms that potentially explain the link between exercise, feeding suppression, and obesity.

The Effects of Exercise on Appetite-Regulating Hormone Concentrations over a 36-h Fast in Healthy Young Adults: A Randomized Crossover Study

Hunger and satiety are controlled by several physiological mechanisms, including pancreatic and gastrointestinal hormones. While the influence of exercise and fasting have been described individually, in relation to these hormones, there is a paucity of work showing the effects of the two modalities (fasting and exercise) combined. Twenty healthy adults (11 males, 9 females) completed both conditions of this study, each consisting of a 36-h water-only fast. One of the fasts began with treadmill exercise, and the differences between the conditions on various appetite hormones were measured every 12 h. The difference in the area under the curve between conditions for ghrelin was 211.8 ± 73.1 pg/mL (F = 8.40, p < 0.0105), and, for GLP-1, it was -1867.9 ± 850.4 pg/mL (F = 4.82, p < 0.0422). No significant differences were noted for areas under the curve between conditions for leptin, PP, PYY, insulin, or GIP. Initiating a fast with exercise lowers ghrelin concentrations and elevates GLP-1 concentrations. Given that ghrelin elicits feelings of hunger and GLP-1 signals feelings of satiety, adding exercise to the beginning of a fast may reduce some of the biological drive of hunger, which could make fasting more tolerable, leading to better adherence and more significant health outcomes.

Effects of exercise training programmes on fasting gastrointestinal appetite hormones in adults with overweight and obesity: A systematic review and meta-analysis

A systematic review and meta-analysis was performed to determine the effect of exercise training on fasting gastrointestinal appetite hormones in adults living with overweight and obesity. For eligibility, only randomised controlled trials (duration ≥ four weeks) examining the effect of exercise training interventions were considered. This review was registered in the International Prospective Register of Systematic Reviews (CRD42020218976). The searches were performed on five databases: MEDLINE, EMBASE, Cochrane Library, Web of Science, and Scopus. The initial search identified 13204 records. Nine studies, which include sixteen exercise interventions, met the criteria for inclusion. Meta-analysis was calculated as the standardised mean difference (Cohen's d). Exercise training had no effect on fasting concentrations of total ghrelin (d: 1.06, 95% CI -0.38 to 2.50, P = 0.15), acylated ghrelin (d: 0.08, 95% CI: -0.31 to 0.47, P = 0.68) and peptide YY (PYY) (d = -0.16, 95% CI: -0.62 to 0.31, P = 0.51) compared to the control group. Analysis of body mass index (BMI) (d: -0.31, 95% CI: -0.50 to -0.12, P < 0.01) and body mass (d: -0.22, 95% CI: -0.42 to -0.03, P = 0.03) found a significant reduction after exercise compared to controls. Overall, exercise interventions did not modify fasting concentrations of total ghrelin, acylated ghrelin, and PYY in individuals with overweight or obesity, although they reduced body mass and BMI. Thus, any upregulation of appetite and energy intake in individuals with overweight and obesity participating in exercise programmes is unlikely to be related to fasting concentrations of gastrointestinal appetite hormones.

A neurocognitive perspective on the relationship between exercise and reward: Implications for weight management and drug addiction

The impact of exercise on food reward is increasingly being discussed as an interplay between executive function (EF), homeostasis and mechanisms promoting or undermining intentional behaviour change. Integrating current knowledge of neurocognitive processes encompassing cognitive and affective networks within an energy balance framework will provide a more comprehensive account. Reward circuitry affected by recreational drugs and food overlap. Therefore the underlying processes explaining changes in drug-taking behaviour may offer new insights into how exercise affects the reward value of recreational drugs and food. EF is important for successful self-regulation, and training EF may boost inhibitory control in relation to food- and drug-related reward. Preclinical and clinical observations suggest that reward-seeking can transfer within and between categories of reward. This may have clinical implications beyond exercise improving metabolic health in people with obesity to understanding therapeutic responses to exercise in people with neurocognitive deficits in non-food reward-based decision making such as drug dependence.

The 13C-bicarbonate technique as a tool for measurement of energy expenditure in overweight dogs undergoing body weight reduction and the effect of different dietary composition

Changes in body size and composition, i.e., body weight (BW) gain or loss, affect the daily energy expenditure (EE). To ensure an appropriate BW reduction and to find an efficient strategy to reduce and maintain a target BW, regular evaluations and adjustments of energy allowance are important. This study aimed to provide a detailed knowledge about the possible changes in resting EE using the oral 13C-bicarbonate technique (o13CBT) as a research tool in 16 overweight pet dogs undergoing BW reduction. Dietary composition (i.e., in % of dry matter [DM] being a high protein [33.3], low fat [9.6], and high crude fiber [18.0] diet [LFHFibre], and a high protein [37.9], high fat [52.0], carbohydrate-free diet [HFat]) during 16 wk of energy restriction were evaluated regarding effects on resting EE, rate of BW reduction, body composition, and plasma concentrations of metabolic hormones involved in energy metabolism and appetite regulation. The mean BW loss was higher (P < 0.05) for the dogs fed the LFHFibre diet (1.1%/wk) than that for dogs fed the HFat diet (0.8%/wk), but the total BW reduction of 14.6% and 12.0% of initial BW did not differ significantly (P > 0.05). Resting EE was lower (P < 0.02) after the BW reduction; 414 kJ (99 kcal)/kg BW0.75/d at the start (week 0) and 326 kJ (78 kcal)/kg BW0.75/d at the end (week 16) of the study. The BW reduction in both groups (P > 0.05) consisted of both fat mass (FM) and fat-free mass (FFM). Energy expenditure, calculated in relation to amount of FFM, was not significantly (P > 0.05) affected by BW reduction. Dietary composition did not significantly affect (P > 0.05) plasma concentrations of insulin, leptin, and ghrelin, and no effect (P > 0.05) of BW reduction was observed on hormone concentrations. In conclusion, the o13CBT proved to be a useful research method for studying short-term EE in overweight dogs. Even though all dogs lost BW, most dogs were still overweight at the end of the study. Due to a high individual variation among dogs, a longer experimental period with a larger sample size would be desirable.

Changes in body mass, appetite-related hormones, and appetite sensation in women during 4 days of hypobaric hypoxic exposure equivalent to 3,500-m altitude

Altitude exposure may suppress appetite and hence provide a viable weight-loss strategy. While changes in food intake and availability as well as physical activity may contribute to altered appetite at altitude, herein we aimed to investigate the isolated effects of hypobaric hypoxia on appetite regulation and sensation. Twelve healthy women (age: 24.0 ± 4.2 years, body mass: 60.6 ± 7.0 kg) completed two 4-day sojourns in a hypobaric chamber, one in normoxia [P_B = 761 mmHg, 262 m (NX)] and one in hypobaric hypoxia [P_B = 493 mmHg (HH)] equivalent to 3,500-m altitude. Energy intake was standardized 4 days prior and throughout both sojourns. Plasma concentrations of leptin, acylated ghrelin, cholecystokinin (CCK), and cytokine growth differentiation factor 15 (GDF15) were determined every morning. Before and after breakfast, lunch, and dinner, appetite was assessed using visual analog scales. Body mass was significantly decreased following HH but not NX (-0.71 ± 0.32 kg vs. -0.05 ± 0.54 kg, condition: P < 0.001). Compared to NX, acylated ghrelin decreased throughout the HH sojourn (condition × time: P = 0.020), while leptin was higher throughout the entire HH sojourn (condition: P < 0.001). No differences were observed in CCK and GDF15 between the sojourns. Feelings of satiety and fullness were higher (condition: P < 0.001 and P = 0.013, respectively), whereas prospective food consumption was lower in HH than in NX (condition: P < 0.001). Our findings suggest that hypoxia exerts an anorexigenic effect on appetite-regulating hormones, suppresses subjective appetite sensation, and can induce weight loss in young healthy women. Among the investigated hormones, acylated ghrelin and leptin most likely explain the observed HH-induced appetite suppression.NEW & NOTEWORTHY This study investigated the effects of hypoxia on appetite regulation in women while strictly controlling for diet, physical activity, menstrual cycle, and environmental conditions. In young women, 4 days of altitude exposure (3,500 m) decreases body weight and circulating acylated ghrelin levels while preserving leptin concentrations. In line with the hormonal changes, altitude exposure induces alterations in appetite sensation, consisting of a decreased feeling of hunger and prospective food intake and an increased feeling of fullness and satiety.

Effects of a 12-Week Diet versus Diet plus Aerobic and Resistance Exercise Program on Acylated and Desacylated Ghrelin, and Ghrelin O-Acyltransferase in Adolescent Girls with Obesity

This study investigated the effects of a 12-week diet versus diet plus aerobic and resistance exercise programme on acylated ghrelin (AG), desacylated ghrelin (DAG), and ghrelin O-acyltransferase (GOAT) concentrations in girls with obesity. We randomised 30 adolescents with obesity to a 12-week aerobic and resistance exercise group (EG) or a control group (CG). At baseline and at 4, 8, and 12 weeks, we measured their body composition, lipid profile, glucose, AG, DAG, and GOAT concentrations. In the EG, the body fat percentage decreased by 2.37% and was significantly lower than that in the CG. The DAG concentrations significantly increased by 48.3% and 27.4% in the EG and CG, respectively. At 4, 8, and 12 weeks, DAG concentrations were significantly higher in the EG than in the CG. AG concentrations were higher at week 12 than at baseline in both groups. In both groups, the GOAT concentrations increased at weeks 8 and 12; however, no between-group differences were observed in the changes in GOAT concentrations. This study showed increased DAG concentrations and non-significant changes in AG and GOAT concentrations after a 12-week aerobic and resistance exercise programme in girls with obesity. These findings suggest that an aerobic and resistance exercise programme influences appetite-regulating hormones, mainly through changes in DAG concentrations.

The endocrine pancreas during exercise in people with and without type 1 diabetes: Beyond the beta-cell

Although important for digestion and metabolism in repose, the healthy endocrine pancreas also plays a key role in facilitating energy transduction around physical exercise. During exercise, decrements in pancreatic β-cell mediated insulin release opposed by increments in α-cell glucagon secretion stand chief among the hierarchy of glucose-counterregulatory responses to decreasing plasma glucose levels. As a control hub for several major glucose regulatory hormones, the endogenous pancreas is therefore essential in ensuring glucose homeostasis. Type 1 diabetes (T1D) is pathophysiological condition characterised by a destruction of pancreatic β-cells resulting in pronounced aberrations in glucose control. Yet beyond the beta-cell perhaps less considered is the impact of T1D on all other pancreatic endocrine cell responses during exercise and whether they differ to those observed in healthy man. For physicians, understanding how the endocrine pancreas responds to exercise in people with and without T1D may serve as a useful model from which to identify whether there are clinically relevant adaptations that need consideration for glycaemic management. From a physiological perspective, delineating differences or indeed similarities in such responses may help inform appropriate exercise test interpretation and subsequent program prescription. With more complex advances in automated insulin delivery (AID) systems and emerging data on exercise algorithms, a timely update is warranted in our understanding of the endogenous endocrine pancreatic responses to physical exercise in people with and without T1D. By placing our focus here, we may be able to offer a nexus of better understanding between the clinical and engineering importance of AIDs requirements during physical exercise.

The effect of acute exercise on pre-prandial ghrelin levels in healthy adults: A systematic review and meta-analysis

BACKGROUND

Ghrelin is a gut hormone with numerous physiological effects, including the regulation of energy balance, insulin sensitivity, vascular health, and body composition. Acylated (AG) and des-acylated (DAG) ghrelin constitute approximately 22 % and 78 % of total plasma ghrelin (TG), respectively. Alterations in the TG concentration and the AG/DAG ratio may be implicated in conditions involving energy imbalances and insulin resistant states (e.g., metabolic syndrome or Type 2 diabetes mellitus). Exercise is a therapeutic option that can potentially optimize ghrelin levels. Understanding the precise intensity and dose of exercise to optimize ghrelin levels may lead to targeted interventions to restore metabolic regulation in obesity and other clinical conditions.

OBJECTIVE

To perform a systematic review and meta-analysis on the effects of acute exercise on pre-prandial levels of TG, AG, and DAG in healthy adults and to determine if sample demographics or exercise doses moderate such effects.

METHODS

Electronic databases (PubMed, Medline, SPORTDiscus, Web of Science, and Google Scholar) were searched with articles published through August 2020. The following criteria was determined a priori for article inclusion: (i) the study was a randomized controlled trial (RCT),(ii) exercise was an acute bout, (iii) the exercise bout for the intervention group(s)/condition was structured, (iv) the control group/condition received no exercise, (v) participants were adults age 18 or older, (vi) ghrelin was sampled through blood, (vii) there was at least one baseline measure and one post-exercise measure of ghrelin, (viii) there were at least 3 timepoints where ghrelin was measured while participants were fasted to allow for pre-prandial total area-under-the-curve (AUC_total) calculation, (ix) participants were healthy with no overt disease, (x) interventions were carried out without any environmental manipulations. Standardized mean difference (SMD) with 95 % confidence intervals were calculated using the restricted maximum likelihood estimation Moderator analyses to determine whether the overall pooled effect was influenced by: sex, ghrelin form, method of ghrelin analysis, age, body mass index, body fat percentage, fitness, intensity of exercise bout, duration of exercise bout, energy expenditure, and length of AUC_total data.

RESULTS

The analysis included 24 studies that consisted of 52 trials, n = 504 (age 27.0 (8.8) years, BMI 24.7 (2.7) kg/m²) and measured AG (n = 38 trials), DAG (n = 7), and TG (n = 7). The overall model indicated that exercise lowered ghrelin levels compared to control (no exercise); (SMD=-0.44, p < 0.001), and exercise intensity exhibited an inverse relationship with ghrelin levels (regression coefficient (ß)=-0.016, p = 0.04). There was no significant difference by ghrelin form (p = 0.18).

DISCUSSION

Acute exercise significantly lowers plasma ghrelin levels, with higher intensity exercise associated with greater ghrelin suppression. The majority of studies applied a moderate intensity exercise bout and measured AG, with limited data on DAG. This exercise dose may be clinically significant in individuals with metabolic dysregulation and energy imbalance as a therapy to optimize AG levels. More work is needed to compare moderate and high intensity exercise and the ghrelin response in clinical populations.

Ghrelin Response to Acute and Chronic Exercise: Insights and Implications from a Systematic Review of the Literature

BACKGROUND

Ghrelin is a peptide hormone predominantly produced by the stomach. It exerts a wide range of functions including stimulating growth hormone release and regulating appetite, food intake, and glucose and lipid metabolism. Since physical exercise affects all these aspects, a particular interest is accorded to the relationship between ghrelin and exercise. This systematic review aimed to summarize the current available data on the topic for a better understanding of the relationship.

METHODS

An extensive computerized search was performed in the PubMed and SPORTDiscus databases for retrieving relevant articles. The search contained the following keywords: ghrelin, appetite-related peptides, gastrointestinal peptides, gastrointestinal hormones, exercise, acute exercise, chronic exercise, training, and physical activity. Studies investigating the effects of acute/chronic exercise on circulating forms of ghrelin were included.

RESULTS

The initial search identified 840 articles. After screening, 80 articles were included. Despite a heterogeneity of studies and a variability of the findings, the review suggests that acute exercise suppresses acyl ghrelin production regardless of the participants and the exercise characteristics. Long- and very long-term exercise training programs mostly resulted in increased total and des-acyl ghrelin production. The increase is more noticeable in overweight/obese individuals, and is most likely due to weight loss resulting from the training program.

CONCLUSION

The review suggests that exercise may impact ghrelin production. While the precise mechanisms are unclear, the effects are likely due to blood flow redistribution and weight loss for acute and chronic exercise, respectively. These changes are expected to be metabolically beneficial. Further research is needed for a better understanding of the relationship between ghrelin and exercise.

The effect of antecedent exercise on the acute stress response and subsequent food consumption: a preliminary investigation

Physical activity has been shown to be protective against many of the deleterious consequences of stress; however, the effects of exercise on stress-induced food consumption are unclear. This study examined the effect of an acute bout of exercise prior to exposure to an acute stressor on subsequent eating behavior, together with the physiological (e.g., heart rate, blood pressure, salivary cortisol) and psychological (e.g., mood, perceived stress) responses to stress. Twenty-three men and women completed four experimental conditions (control, exercise only, stress only, and exercise prior to stress) conducted in a counterbalanced order using a within-subjects repeated measures design. Ad libitum energy intake from a laboratory test meal was assessed at each trial, together with monitoring of physiological and psychological responses. No difference in total energy intake (p = 0.146) or energy intake from 'unhealthy' foods was noted between conditions (p = 0.783), despite lower circulating ghrelin when antecedent exercise was performed compared with stress alone (p < 0.05). Exposure to an acute stressor is not necessarily associated with alterations in subsequent food intake, nor does antecedent exercise prior to stress exposure affect food choices, despite transient alterations in the hunger hormone ghrelin.

Exercise Shifts Hypothetical Food Choices toward Greater Amounts and More Immediate Consumption

Although exercise modulates appetite regulation and food intake, it remains poorly understood how exercise impacts decision-making about food. The purpose of the present study was to assess the impact of an acute exercise bout on hypothetical choices related to the amount and timing of food intake. Forty-one healthy participants (22.0 ± 2.6 years; 23.7 ± 2.5 kg/m², 56% female) completed 45 min of aerobic exercise and a resting control condition in randomized order. Food amount preferences and intertemporal food preferences (preference for immediate vs. delayed consumption) were assessed using electronic questionnaires with visual food cues. Compared to rest, exercise resulted in a greater increase in the food amount selected, both immediately post-exercise (+25.8 ± 11.0 vs. +7.8 ± 11.0 kcal/item, p = 0.02) and 30 min post-exercise (+47.3 ± 12.4 vs. +21.3 ± 12.4 kcal/item, p = 0.005). Exercise further resulted in a greater increase in the preference for immediate consumption immediately post-exercise (+0.23 ± 0.10 vs. +0.06 ± 0.10; p = 0.03) and 30 min post-exercise (+0.30 ± 0.12 vs. +0.08 ± 0.12; p = 0.01). Our findings demonstrate that a single bout of aerobic exercise shifts hypothetical food choices toward greater amounts and more immediate consumption, highlighting the importance of the timing of food choices made in the exercise context.

Oxidative stress in exercise training: the involvement of inflammation and peripheral signals

The evidence about the health benefits of regular physical activity is well established. Exercise intensity is a significant variable and structured high-intensity interval training (HIIT) has been demonstrated to improve both whole-body and skeletal muscle metabolic health in different populations. Conversely, fatigue accumulation, if not resolved, leads to overwork, chronic fatigue syndrome (CFS), overtraining syndrome up to alterations of endocrine function, immune, systemic inflammation, and organic diseases with health threat. In response to temporary increases in stress during training, some athletes are unable to maintain sufficient caloric intake, thus suffering a negative energy balance that causes further stress. The regulation of the energy balance is controlled by the central nervous system through an elaborate interaction of the signalling that involves different tissues such as leptin, adiponectin and ghrelin whose provide important feedback to the hypothalamus to regulate the energy balance. Although exercise-induced reactive oxygen species are required for normal force production in muscle, high levels of ROS appear to promote contractile dysfunction. However, a high level of oxidative stress in may induce a rise in inflammatory markers and a disregulation in expression of adiponectin, leptin and grelin.

The effects of high intensity interval training on appetite management in individuals with type 2 diabetes: influenced by participants weight

Background and purpose

The connection between exercise and appetite has ramifications for acute energy balance and weight-management. Research would suggest that exercise training can transiently suppress appetite, particularly in overweight and T2D, healthy-weight individuals. However, the effect of such a transient appetite suppression on subsequent food intake may be restricted. The aim of this thesis was to investigate appetite responses to HIIT in obesity with T2D and to assess the effect of other exercise characteristics, as well as exercise intensity, in mediating these responses especially appetite hormones.

Materials and methods

Eighty individuals with type 2 diabetes (forty normal and forty obesity weight) performed HIIT trials, all in arandomly divided, in 8 groups (10 in each group) which included, obesity non-diabetic control, obesity diabetic control, normal weight diabetic control, obesity non-diabetic training, obesity diabetic training, normal weight, non-diabetic training, and normal weight diabetic training. Twelve-weeks HIIT sessions (each session of an interval training includes 60 s of high intensity training (85-95% of reserve heart rate)) + running for 60 s at low intensity (55-60% of reserve heart rate) were applied. Blood samples were taken at the beginning and after the fourth, eighth and twelfth week of the training. Data were analyzed using repeated variance analysis and Pearson correlation coefficient.

Results

The results showed that training reduced ghrelin plasma levels in obese diabetic subjects (P < 0.05). Training has reduced PYY plasma in healthy subjects (non-diabetic) with normal weight (P < 0.05). Training reduced plasma levels of PYY in diabetic patients with normal weight and increased it in obese diabetic and healthy subjects (P < 0.05). Training has increased GLP-1 plasma in obese diabetic and diabetic with normal weight groups (P < 0.05). Training reduced TNF-α in normal (non-diabetic) subjects with normal weight and diabetic and non-diabetic obese subjects.

Conclusion

Collectively, the studies reported here suggest that appetite hormones differ between lean and obesity participants. The finding also suggested HIIT is more likely to elicit appetite hormones responses in obesity than in lean individuals with type 2 diabetes. Therefore, with caution, it is recommended that the high intensity interval training can be beneficial for these patients.

Physiology of energy homeostasis: Models, actors, challenges and the glucoadipostatic loop

The aim of this review is to discuss the physiology of energy homeostasis (EH), which is a debated concept. Thus, we will see that the set-point theory is highly challenged and that other models integrating an anticipative component, such as energy allostasis, seem more relevant to experimental reports and life preservation. Moreover, the current obesity epidemic suggests that EH is poorly efficient in the modern human dietary environment. Non-homeostatic phenomena linked to hedonism and reward seem to profoundly impair EH. In this review, the apparent failed homeostatic responses to energy challenges such as exercise, cafeteria diet, overfeeding and diet-induced weight loss, as well as their putative determinants, are analyzed to highlight the mechanisms of EH. Then, the hormonal, neuronal, and metabolic factors of energy intake or energy expenditure are briefly presented. Last, this review focuses on the contributions of two of the most pivotal and often overlooked determinants of EH: the availability of endogenous energy and the pattern of energy intake. A glucoadipostatic loop model is finally proposed to link energy stored in adipose tissue to EH through changes in eating behavior via leptin and sympathetic nervous system activity.

Acute and Chronic Effects of Exercise on Appetite, Energy Intake, and Appetite-Related Hormones: The Modulating Effect of Adiposity, Sex, and Habitual Physical Activity

Exercise facilitates weight control, partly through effects on appetite regulation. Single bouts of exercise induce a short-term energy deficit without stimulating compensatory effects on appetite, whilst limited evidence suggests that exercise training may modify subjective and homeostatic mediators of appetite in directions associated with enhanced meal-induced satiety. However, a large variability in responses exists between individuals. This article reviews the evidence relating to how adiposity, sex, and habitual physical activity modulate exercise-induced appetite, energy intake, and appetite-related hormone responses. The balance of evidence suggests that adiposity and sex do not modify appetite or energy intake responses to acute or chronic exercise interventions, but individuals with higher habitual physical activity levels may better adjust energy intake in response to energy balance perturbations. The effect of these individual characteristics and behaviours on appetite-related hormone responses to exercise remains equivocal. These findings support the continued promotion of exercise as a strategy for inducing short-term energy deficits irrespective of adiposity and sex, as well as the ability of exercise to positively influence energy balance over the longer term. Future well-controlled studies are required to further ascertain the potential mediators of appetite responses to exercise.

A Role for Exercise in Attenuating Unhealthy Food Consumption in Response to Stress

It is well established that both acute and chronic stress can be detrimental to health and wellbeing by directly increasing the risk of several chronic diseases and related health problems. In addition, stress may contribute to ill-health indirectly via its downstream effects on individuals’ health-related behaviour, such as promoting the intake of unhealthy palatable foods high in fat and sugar content. This paper reviews (a) the research literature on stress-models; (b) recent research investigating stress-induced eating and (c) the potential physiological and psychological pathways contributing to stress-induced eating. Particular attention is given to (d) the role of physical exercise in attenuating acute stress, with exploration of potential mechanisms through which exercise may reduce unhealthy food and drink consumption subsequent to stressor exposure. Finally, exercise motivation is discussed as an important psychological influence over the capacity for physical exercise to attenuate unhealthy food and drink consumption after exposure to stressors. This paper aims to provide a better understanding of how physical exercise might alleviate stress-induced unhealthy food choices.

Effects of walking in water on gut hormone concentrations and appetite: comparison with walking on land

The effects of water exercise on gut hormone concentrations and appetite currently remain unclear. The aim of the present study was to investigate the effects of treadmill walking in water on gut hormone concentrations and appetite. Thirteen men (mean ± s.d. age: 21.6 ± 2.2 years, body mass index: 22.7 ± 2.8 kg/m², peak oxygen uptake (VO_2peak): 49.8 ± 7.8 mL/kg per min) participated in the walking in water and on land challenge. During the study period, ratings of subjective feelings of hunger, fullness, satiety and motivation to eat were reported on a 100-mm visual analog scale. A test meal was presented after walking, and energy intake (EI) was calculated. Blood samples were obtained during both trials to measure glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and acylated ghrelin (AG) concentrations. Hunger scores (How hungry do you feel?) were significantly lower during the water trial than during the land trial (P < 0.05). No significant differences were observed in EI between water and land trials. GLP-1 concentrations were significantly higher in the water trial than in the land trial (P < 0.05). No significant differences were observed in PYY concentrations between water and land trials. AG concentrations were significantly lower in the water trial than in the land trial (P < 0.01). In conclusion, changes in gut hormone concentrations during walking in water contribute to the exercise-induced suppression of appetite and provide novel information on the influence of walking in water on the acute regulation of appetite.

Multiplexed Temporal Quantification of the Exercise-regulated Plasma Peptidome

Exercise is extremely beneficial to whole body health reducing the risk of a number of chronic human diseases. Some of these physiological benefits appear to be mediated via the secretion of peptide/protein hormones into the blood stream. The plasma peptidome contains the entire complement of low molecular weight endogenous peptides derived from secretion, protease activity and PTMs, and is a rich source of hormones. In the current study we have quantified the effects of intense exercise on the plasma peptidome to identify novel exercise regulated secretory factors in humans. We developed an optimized 2D-LC-MS/MS method and used multiple fragmentation methods including HCD and EThcD to analyze endogenous peptides. This resulted in quantification of 5,548 unique peptides during a time course of exercise and recovery. The plasma peptidome underwent dynamic and large changes during exercise on a time-scale of minutes with many rapidly reversible following exercise cessation. Among acutely regulated peptides, many were known hormones including insulin, glucagon, ghrelin, bradykinin, cholecystokinin and secretogranins validating the method. Prediction of bioactive peptides regulated with exercise identified C-terminal peptides from Transgelins, which were increased in plasma during exercise. In vitro experiments using synthetic peptides identified a role for transgelin peptides on the regulation of cell-cycle, extracellular matrix remodeling and cell migration. We investigated the effects of exercise on the regulation of PTMs and proteolytic processing by building a site-specific network of protease/substrate activity. Collectively, our deep peptidomic analysis of plasma revealed that exercise rapidly modulates the circulation of hundreds of bioactive peptides through a network of proteases and PTMs. These findings illustrate that peptidomics is an ideal method for quantifying changes in circulating factors on a global scale in response to physiological perturbations such as exercise. This will likely be a key method for pinpointing exercise regulated factors that generate health benefits.

Acute effects of exercise on appetite, ad libitum energy intake and appetite-regulatory hormones in lean and overweight/obese men and women

BACKGROUND

Acute exercise does not elicit compensatory changes in appetite parameters in lean individuals; however, less is known about responses in overweight individuals. This study compared the acute effects of moderate-intensity exercise on appetite, energy intake and appetite-regulatory hormones in lean and overweight/obese individuals.

METHODS

Forty-seven healthy lean (n=22, 11 females; mean (s.d.) 37.5 (15.2) years; 22.4 (1.5) kg m^-2) and overweight/obese (n=25, 11 females; 45.0 (12.4) years, 29.2 (2.9) kg m^-2) individuals completed two, 8 h trials (exercise and control). In the exercise trial, participants completed 60 min treadmill exercise (59 (4)% peak oxygen uptake) at 0-1 h and rested thereafter while participants rested throughout the control trial. Appetite ratings and concentrations of acylated ghrelin, peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) were measured at predetermined intervals. Standardised meals were consumed at 1.5 and 4 h and an ad libitum buffet meal was provided at 7 h.

RESULTS

Exercise suppressed appetite (95% confidence interval (CI) -3.1 to -0.5 mm, P=0.01), and elevated delta PYY (95% CI 10 to 17 pg ml^-1, P<0.001) and GLP-1 (95% CI 7 to 10 pmol l^-1, P<0.001) concentrations. Delta acylated ghrelin concentrations (95% CI -5 to 3 pg ml^-1, P=0.76) and ad libitum energy intake (95% CI -391 to 346 kJ, P=0.90) were similar between trials. Subjective and hormonal appetite parameters and ad libitum energy intake were similar between lean and overweight/obese individuals (P⩾0.27). The exercise-induced elevation in delta GLP-1 was greater in overweight/obese individuals (trial-by-group interaction P=0.01), whereas lean individuals exhibited a greater exercise-induced increase in delta PYY (trial-by-group interaction P<0.001).

CONCLUSIONS

Acute moderate-intensity exercise transiently suppressed appetite and increased PYY and GLP-1 in the hours after exercise without stimulating compensatory changes in appetite in lean or overweight/obese individuals. These findings underscore the ability of exercise to induce a short-term energy deficit without any compensatory effects on appetite regardless of weight status.

Acute effect of exercise intensity and duration on acylated ghrelin and hunger in men

Acute exercise transiently suppresses the orexigenic gut hormone acylated ghrelin, but the extent to which exercise intensity and duration determine this response is not fully understood. The effects of manipulating exercise intensity and duration on acylated ghrelin concentrations and hunger were examined in two experiments. In experiment one, nine healthy males completed three, 4-h conditions (control, moderate-intensity running (MOD) and vigorous-intensity running (VIG)), with an energy expenditure of ~2.5 MJ induced in both MOD (55-min running at 52% peak oxygen uptake (V.O_2peak)) and VIG (36-min running at 75% V.O_2peak). In experiment two, nine healthy males completed three, 9-h conditions (control, 45-min running (EX45) and 90-min running (EX90)). Exercise was performed at 70% V.O_2peak In both experiments, participants consumed standardised meals, and acylated ghrelin concentrations and hunger were quantified at predetermined intervals. In experiment one, delta acylated ghrelin concentrations were lower than control in MOD (ES = 0.44, P = 0.01) and VIG (ES = 0.98, P < 0.001); VIG was lower than MOD (ES = 0.54, P = 0.003). Hunger ratings were similar across the conditions (P = 0.35). In experiment two, delta acylated ghrelin concentrations were lower than control in EX45 (ES = 0.77, P < 0.001) and EX90 (ES = 0.68, P < 0.001); EX45 and EX90 were similar (ES = 0.09, P = 0.55). Hunger ratings were lower than control in EX45 (ES = 0.20, P = 0.01) and EX90 (ES = 0.27, P = 0.001); EX45 and EX90 were similar (ES = 0.07, P = 0.34). Hunger and delta acylated ghrelin concentrations remained suppressed at 1.5 h in EX90 but not EX45. In conclusion, exercise intensity, and to a lesser extent duration, are determinants of the acylated ghrelin response to acute exercise.

Appetite and Energy Intake Responses to Acute Energy Deficits in Females versus Males

Purpose

To explore whether compensatory responses to acute energy deficits induced by exercise or diet differ by sex.

Methods

In experiment one, 12 healthy women completed three 9-h trials (control, exercise-induced (Ex-Def) and food restriction–induced energy deficit (Food-Def)) with identical energy deficits being imposed in the Ex-Def (90-min run, ∼70% of V˙O_2max) and Food-Def trials. In experiment two, 10 men and 10 women completed two 7-h trials (control and exercise). Sixty minutes of running (∼70% of V˙O_2max) was performed at the beginning of the exercise trial. The participants rested throughout the remainder of the exercise trial and during the control trial. Appetite ratings, plasma concentrations of gut hormones, and ad libitum energy intake were assessed during main trials.

Results

In experiment one, an energy deficit of approximately 3500 kJ induced via food restriction increased appetite and food intake. These changes corresponded with heightened concentrations of plasma acylated ghrelin and lower peptide YY_3–36. None of these compensatory responses were apparent when an equivalent energy deficit was induced by exercise. In experiment two, appetite ratings and plasma acylated ghrelin concentrations were lower in exercise than in control, but energy intake did not differ between trials. The appetite, acylated ghrelin, and energy intake response to exercise did not differ between men and women.

Conclusions

Women exhibit compensatory appetite, gut hormone, and food intake responses to acute energy restriction but not in response to an acute bout of exercise. Additionally, men and women seem to exhibit similar acylated ghrelin and PYY_3–36 responses to exercise-induced energy deficits. These findings advance understanding regarding the interaction between exercise and energy homeostasis in women.

Exercise, Appetite and Weight Control: Are There Differences between Men and Women?

Recent years have witnessed significant research interest surrounding the interaction among exercise, appetite and energy balance, which has important implications for health. The majority of exercise and appetite regulation studies have been conducted in males. Consequently, opportunities to examine sex-based differences have been limited, but represent an interesting avenue of inquiry considering postulations that men experience greater weight loss after exercise interventions than women. This article reviews the scientific literature relating to the acute and chronic effects of exercise on appetite control in men and women. The consensus of evidence demonstrates that appetite, appetite-regulatory hormone and energy intake responses to acute exercise do not differ between the sexes, and there is little evidence indicating compensatory changes occur after acute exercise in either sex. Limited evidence suggests women respond to the initiation of exercise training with more robust compensatory alterations in appetite-regulatory hormones than men, but whether this translates to long-term differences is unknown. Current exercise training investigations do not support sex-based differences in appetite or objectively assessed energy intake, and increasing exercise energy expenditure elicits at most a partial energy intake compensation in both sexes. Future well-controlled acute and chronic exercise studies directly comparing men and women are required to expand this evidence base.

Breaking up prolonged sitting time with walking does not affect appetite or gut hormone concentrations but does induce an energy deficit and suppresses postprandial glycaemia in sedentary adults

Breaking up periods of prolonged sitting can negate harmful metabolic effects but the influence on appetite and gut hormones is not understood and is investigated in this study. Thirteen sedentary (7 female) participants undertook three 5-h trials in random order: (i) uninterrupted sitting (SIT), (ii) seated with 2-min bouts of light-intensity walking every 20 min (SIT + LA), and (iii) seated with 2-min bouts of moderate-intensity walking every 20 min (SIT + MA). A standardised test drink was provided at the start of each trial and an ad libitum pasta test meal provided at the end of each trial. Subjective appetite ratings and plasma acylated ghrelin, peptide YY, insulin, and glucose were measured at regular intervals. Area under the curve (AUC) was calculated for each variable. AUC values for appetite and gut hormone concentrations were unaffected in the activity breaks conditions compared with uninterrupted sitting (linear mixed modelling: p > 0.05). Glucose AUC was lower in SIT + MA than in SIT + LA (p = 0.004) and SIT (p = 0.055). There was no difference in absolute ad libitum energy intake between conditions (p > 0.05); however, relative energy intake was lower in SIT + LA (39%; p = 0.011) and SIT + MA (120%; p < 0.001) than in SIT. In conclusion, breaking up prolonged sitting does not alter appetite and gut hormone responses to a meal over a 5-h period. Increased energy expenditure from activity breaks could promote an energy deficit that is not compensated for in a subsequent meal.

The oral [(13)C]bicarbonate technique for measurement of short-term energy expenditure of sled dogs and their physiological response to diets with different fat:carbohydrate ratios

The oral [¹³C]bicarbonate technique (o¹³CBT) was assessed for the determination of short-term energy expenditure (EE) under field conditions. A total of eight Alaskan huskies were fed two experimental diets in a cross-over experiment including two periods of 3 weeks. Effects of diets on EE, apparent total tract digestibility (ATTD) and on plasma hormones, blood lactate and glucose were furthermore investigated. The percentages of metabolisable energy derived from protein (P), fat (F) and carbohydrates (C) were 26:58:16 in the PFC diet and 24:75:1 in the PF diet. Measurements of EE were performed in the post-absorptive state during rest. Blood samples were collected during rest and exercise and ATTD was determined after days with rest and with exercise. EE was higher (P < 0·01) in period 2 than in period 1 (68 v. 48 kJ/kg body weight^0·75 per h). The ATTD of organic matter, crude protein and crude fat was higher (P < 0·01) in the PF diet compared with the PFC diet, and lower (P < 0·01) for total carbohydrates. Exercise did not affect ATTD. Higher (P < 0·01) insulin-like growth factor 1 and leptin concentrations were measured when fed the PF diet compared with the PFC diet. Concentrations of insulin decreased (P < 0·01), whereas cortisol and ghrelin increased (P < 0·05), after exercise. There was no effect of diet on blood lactate and glucose, but higher (P < 0·001) lactate concentrations were measured in period 1 than in period 2. The results suggest that the o¹³CBT can be used in the field to estimate short-term EE in dogs during resting conditions. Higher ATTD and energy density of the PF diet may be beneficial when energy requirements are high.

Appetite, appetite hormone and energy intake responses to two consecutive days of aerobic exercise in healthy young men

Single bouts of exercise do not cause compensatory changes in appetite, food intake or appetite regulatory hormones on the day that exercise is performed. It remains possible that such changes occur over an extended period or in response to a higher level of energy expenditure. This study sought to test this possibility by examining appetite, food intake and appetite regulatory hormones (acylated ghrelin, total peptide-YY, leptin and insulin) over two days, with acute bouts of exercise performed on each morning. Within a controlled laboratory setting, 15 healthy males completed two, 2-day long (09:00-16:00) experimental trials (exercise and control) in a randomised order. On the exercise trial participants performed 60 min of continuous moderate-high intensity treadmill running (day one: 70.1 ± 2.5% VO2peak, day two: 70.0 ± 3.2% VO2max (mean ± SD)) at the beginning of days one and two. Across each day appetite perceptions were assessed using visual analogue scales and appetite regulatory hormones were measured from venous blood samples. Ad libitum energy and macronutrient intakes were determined from meals provided two and six hours into each day and from a snack bag provided in-between trial days. Exercise elicited a high level of energy expenditure (total = 7566 ± 635 kJ across the two days) but did not produce compensatory changes in appetite or energy intake over two days (control: 29,217 ± 4006 kJ; exercise: 28,532 ± 3899 kJ, P > 0.050). Two-way repeated measures ANOVA did not reveal any main effects for acylated ghrelin or leptin (all P > 0.050). However a significant main effect of trial (P = 0.029) for PYY indicated higher concentrations on the exercise vs. control trial. These findings suggest that across a two day period, high volume exercise does not stimulate compensatory appetite regulatory changes.

Exercise-trained men and women: role of exercise and diet on appetite and energy intake

The regulation of appetite and energy intake is influenced by numerous hormonal and neural signals, including feedback from changes in diet and exercise. Exercise can suppress subjective appetite ratings, subsequent energy intake, and alter appetite-regulating hormones, including ghrelin, peptide YY, and glucagon-like peptide 1(GLP-1) for a period of time post-exercise. Discrepancies in the degree of appetite suppression with exercise may be dependent on subject characteristics (e.g., body fatness, fitness level, age or sex) and exercise duration, intensity, type and mode. Following an acute bout of exercise, exercise-trained males experience appetite suppression, while data in exercise-trained women are limited and equivocal. Diet can also impact appetite, with low-energy dense diets eliciting a greater sense of fullness at a lower energy intake. To date, little research has examined the combined interaction of exercise and diet on appetite and energy intake. This review focuses on exercise-trained men and women and examines the impact of exercise on hormonal regulation of appetite, post-exercise energy intake, and subjective and objective measurements of appetite. The impact that low-energy dense diets have on appetite and energy intake are also addressed. Finally, the combined effects of high-intensity exercise and low-energy dense diets are examined. This research is in exercise-trained women who are often concerned with weight and body image issues and consume low-energy dense foods to keep energy intakes low. Unfortunately, these low-energy intakes can have negative health consequences when combined with high-levels of exercise. More research is needed examining the combined effect of diet and exercise on appetite regulation in fit, exercise-trained individuals.

Effect of acute and regular exercise on growth hormone secretagogue receptor-1a expression in human lymphocytes, T cell subpopulation and monocytes

The orexigenic peptide hormone ghrelin exerts potent inhibitory effects on pro-inflammatory cytokine release via the growth hormone secretagogue receptor-1a (GHS-R1a) on T cells and monocytes. As such, ghrelin is a promising therapeutic agent for the treatment of inflammatory conditions, but these effects depend on the availability of GHS-R1a. The aim of this study was to determine the effect of acute exercise on GHS-R1a expression on circulating CD14+ monocytes, total lymphocytes and CD3+ T cells. Nine male club-standard cyclists cycled for 1h at 75% V̇O2peak (EX) or rested (REST) in a randomised cross-over design. Compared with the equivalent times in REST, the concentration of circulating GHS-R1a+ lymphocytes and monocytes was higher in EX at immediately and 1 and 2h post-exercise (all p<.05). The concentration of CD3+GHS-R1a+ cells was higher in EX than in REST immediately post-exercise only (258 (203)cellsμl(-1) vs. 62 (42)cellsμl(-1), p<.05). Density of GHS-R1a receptor expression was unaffected by trial or time. Comparison of active participants at rest with 7 age-, sex- and BMI-matched sedentary controls revealed a higher concentration of GHS-R1a+ lymphocytes in active males (p<.05). These findings suggest a preferential recruitment of specific cell subpopulations expressing GHS-R1a into the peripheral circulation with acute and regular exercise. Given that the anti-inflammatory effects of ghrelin depend on the availability of GHS-R1a, the preferential recruitment of subpopulations with high anti-inflammatory potential found here add a novel aspect to the potential mechanisms by which exercise acts to reduce pro-inflammatory cytokine levels.

The Psychophysical Connection Between Exercise, Hunger, and Energy Intake

Exercise is vitally important in the prevention of weight gain or maintaining weight status, as well as weight loss. High-intensity exercise causes a short-term suppression of hunger of approximately 15 to 60 minutes. Although there is evidence for compensatory food consumption, it usually does not make up for the energy deficit created by exercise. The exception occurs when individuals consume or reward themselves with energy-dense foods or drink. Because people tend to eat the same volume of food each day, on days when they exercise, they will remain in an energy deficit. However, on sedentary days, a positive energy balance is likely if caloric restriction is not imposed, which could result in weight gain. Caloric restriction alone leads to loss of lean body mass, while the inclusion of exercise with an energy deficit helps conserve lean tissue. There are a myriad physiological factors such as the concentration of hormones (GLP-1, PYY3-36, leptin, and ghrelin) and metabolites (free fatty acids and glucose) that either stimulate or inhibit signals for hunger and/or energy intake, but the effect of exercise on these circulating factors is complex and not completely understood.