Effects of high-intensity intermittent exercise training on appetite regulation

Objective: An acute bout of high intensity intermittent exercise suppresses ad-libitum energy intake at the post-exercise meal. The present study examined the effects of 12 weeks of high intensity intermittent exercise training (HIIT) compared with moderate intensity continuous exercise training (MICT) on appetite regulation. Methods: Thirty overweight, inactive men (BMI: 27.2 +/- 1.3 kg/m2; V[spacing dot above]O2Peak: 35.3 +/- 5.3 mL.kg-1.min-1) were randomised to either HIIT or MICT (involving 12 weeks of training, 3 sessions per week) or a control group (CON) (n = 10 per group). Ad-libitum energy intake from a laboratory test meal was assessed following both a low-energy (LEP: 847 kJ) and a high-energy preload (HEP: 2438 kJ) pre and post-intervention. Perceived appetite and appetite-related blood variables were also measured. Results: There was no significant effect of the intervention period on energy intake at the test meal following the two different preloads (p >= 0.05). However, the 95% CI indicated a clinically meaningful decrease in energy intake after the HEP compared with LEP in response to HIIT (516 +/- 395 kJ decrease), but not for MICT or CON, suggesting improved appetite regulation. This was not associated with alterations in the perception of appetite or the circulating concentration of a number of appetite-related peptides or metabolites, although insulin sensitivity was enhanced with HIIT only (p = 0.003). Conclusion: HIIT appears to benefit appetite regulation in overweight men. The mechanisms for this remain to be elucidated

The effect of exercise timing on Glycemic Control

Despite the acknowledgment of exercise as a cornerstone in the management of type 2 diabetes (T2D), the importance of exercise timing has only recently been considered

High-intensity intermittent exercise attenuates ad-libitum energy intake

Objective: To examine the acute effects of high-intensity intermittent exercise (HIIE) on energy intake, perceptions of appetite and appetite-related hormones in sedentary, overweight men. Design: Seventeen overweight men (body mass index: 27.7±1.6 kg m−2; body mass: 89.8±10.1 kg; body fat: 30.0±4.3%; VO2peak: 39.2±4.8 ml kg−1 min−1) completed four 30-min experimental conditions using a randomised counterbalanced design. CON: resting control, MC: continuous moderate-intensity exercise (60% VO2peak), HI: high-intensity intermittent exercise (alternating 60 s at 100% VO2peak and 240 s at 50% VO2peak), VHI: very-high-intensity intermittent exercise (alternating 15 s at 170% VO2peak and 60 s at 32% VO2peak). Participants consumed a standard caloric meal following exercise/CON and an ad-libitum meal 70 min later. Capillary blood was sampled and perceived appetite assessed at regular time intervals throughout the session. Free-living energy intake and physical activity levels for the experimental day and the day after were also assessed. Results: Ad-libitum energy intake was lower after HI and VHI compared with CON (P=0.038 and P=0.004, respectively), and VHI was also lower than MC (P=0.028). Free-living energy intake in the subsequent 38 h remained less after VHI compared with CON and MC (P 0.050). These observations were associated with lower active ghrelin (P 0.050), higher blood lactate (P 0.014) and higher blood glucose (P 0.020) after VHI compared with all other trials. Despite higher heart rate and ratings of perceived exertion (RPE) during HI and VHI compared with MC (P 0.004), ratings of physical activity enjoyment were similar between all the exercise trials (P=0.593). No differences were found in perceived appetite between trials. Conclusions: High-intensity intermittent exercise suppresses subsequent ad-libitum energy intake in overweight inactive men. This format of exercise was found to be well tolerated in an overweight population

Effect of diurnal exercise timing on postprandial glucose responses: A randomized controlled trial

PURPOSE: Postprandial exercise has been shown to reduce postprandial glucose (PPG) response to a greater degree than preprandial exercise, suggesting an important yet under-acknowledged role for exercise timing on glycemic control. Whether diurnal timing of exercise imparts additional benefits on PPG responses remains unclear. This study aimed to determine the diurnal effect of exercise timing on PPG response in individuals enrolled into a 12-week supervised multi-modal exercise training program. METHODS: Forty sedentary overweight individuals (17 males, 23 female; age: 51 ± 13 years; BMI: 30.9 ± 4.2 kg/m2) with (n = 20) or without T2DM diagnosis were randomly allocated to either a morning (amEX) or evening (pmEX) exercise training group. All participants completed the 12-week supervised multi-modal exercise training program (3 days per week), which consisted of 30 minutes of aerobic exercise (walking protocol) and 4 resistance-based exercises (3 sets of 12-18 repetitions). The amEX and pmEX training sessions occurred in the postprandial state between 0700-0900h and 1700-1900h, respectively. Changes in postprandial glucose (PPG) and insulin (PPI) responses, during a mixed meal tolerance test (MMTT) were the primary outcome measures of the study assessed at baseline and post-intervention at 12 weeks. All data is displayed as mean differences ± SD. RESULTS: Exercise training reduced (main effect of time, p < 0.01) PPG and PPI concentrations during the MMTT, with no group differences observed (p = 0.69). A significantly greater reduction in PPG-iAUC was observed for the pmEX group (-78.56 mmol/L) when compared to the amEX group (-33.22 mmol/L) at post-intervention (p = 0.03). Reductions in PPI iAUC (main effect of time, p < 0.01) were observed at post-intervention, with no group differences reported (p = 0.18) CONCLUSIONS: Irrespective of the diurnal timing of exercise performance, 12-weeks of multi-modal exercise training significant improved PPG and PPI responses in both overweight non-T2DM and T2DM individuals

Mild dehydration does not reduce postexercise appetite or energy intake

Purpose: It has now been established that exercise performed under various environmental conditions may affect acute energy intake and appetite-related hormones. The exact mechanism linking acute energy intake and exercise remains unknown, although indirect evidence suggests a possible role for hydration status. Therefore, the purpose of this study was to investigate the interaction of exercise and hydration status on subsequent energy intake and appetite-related hormones. Methods: In a randomized, counterbalanced design, 10 physically active males completed three experimental trials in a fasted state: exercise when hydrated (0%-1% of body mass), exercise when dehydrated (-1% to -2% of body mass), and a hydrated resting control. Exercise consisted of treadmill running for 45 min at 70% (V) over dotO(2peak). Participants were then given access to a buffet-style breakfast from which they could consume ad libitum. Blood was sampled regularly during trials for appetite-related hormones. Results: There were no significant differences in total energy intake between trials (P = 0.491); however, relative energy intake was significantly higher in the control (4839 +/- 415 kJ, P < 0.001) compared to hydrated (1749 +/- 403 kJ) and dehydrated exercise (1656 +/- 413 kJ) conditions. Exercise performed in a dehydrated state resulted in significantly lower concentrations of ghrelin compared with control (P = 0.045) and hydrated exercise conditions (P = 0.014). Conclusions: Exercise significantly decreased relative energy intake compared with resting control; however, energy intake (relative and total) was no different between the exercise conditions (dehydrated vs hydrated). Despite similar energy intake between trials, exercise in a dehydrated state resulted in a significantly lower concentration of ghrelin, a hormone responsible for stimulating appetite

Response to ‘Post-exercise energy load and activities may affect subsequent ad libitum energy intake’

As pointed out by Thivel et al., the use of the fixed caloric load in the form of a liquid meal was to allow for a standardized comparison of the appetite-related blood variables. The authors suggest that the participants may have experienced different digestive acceptances and gastric emptying rates of the liquid meal, which may have affected energy intake in the subsequent ad libitum meal. While there is some evidence to suggest that gastric emptying may be affected by the intensity of exercise during exercise, there has been minimal research examining gastric emptying rates post exercise. The limited evidence available suggests that there are no differences in gastric emptying rates after either rest compared with low-intensity and high-intensity exercise. Regardless, any effect on gastric emptying rate does not change the conclusion that participants consumed less following high-intensity intermittent exercise—it simply offers an alternative explanation for the mechanism underlying this effect

Response

Special communications: Letters to the editor-in-chie

Energy intake and appetite-related hormones following acute aerobic and resistance exercise

Previous research has shown that resistance and aerobic exercise have differing effects on perceived hunger and circulating levels of appetite-related hormones. However, the effect of resistance and aerobic exercise on actual energy intake has never been compared. This study investigated the effect of an acute bout of resistance exercise, compared with aerobic exercise, on subsequent energy intake and appetite-regulating hormones. Ten active men completed 3 trials in a counterbalanced design: 45 min of resistance exercise (RES; free and machine weights), aerobic exercise (AER; running), or a resting control trial (CON). Following exercise or CON, participants had access to a buffet-style array of breakfast foods and drinks to consume ad libitum. Plasma concentrations of a range of appetite-regulating hormones were measured throughout each trial. Despite significantly higher energy expenditure with AER compared with RES (p < 0.05), there was no difference in total energy intake from the postexercise meal between trials (p = 0.779). Pancreatic polypeptide was significantly higher prior to the meal after both RES and AER compared with CON. In contrast, active ghrelin was lower following RES compared with both CON and AER (p ≤ 0.05), while insulin was higher following RES compared with CON (p = 0.013). In summary, the differential response of appetite-regulating hormones to AER and RES does not appear to influence energy intake in the postexercise meal. However, given the greater energy expenditure associated with AER compared with RES, AER modes of exercise may be preferable for achieving short-term negative energy balance

Exercise timing in type 2 diabetes mellitus

Purpose The timing of exercise relative to meal consumption has recently been identified as potentially moderating the effectiveness of exercise on glycemic responses in type 2 diabetes mellitus (T2DM). The aim of this study was to systematically review the literature related to exercise timing, relative to meal consumption, and glycemic control in individuals with T2DM. Methods Systematic searches in PubMed, EMBASE, CINAHL, Cochrane Library, and ClinicalTrials.gov Registry databases were performed to identify articles published in English from inception to October 2017. Two authors independently extracted data and evaluated the quality of studies using the Cochrane Collaboration Data Collection Form and the Cochrane Collaboration Risk of Bias Assessment Tool, respectively. A qualitative synthesis was performed on the included studies, and results summarized in tables. Results Nineteen randomized controlled trials with a total of 346 participants were included. Improvements in glycemia (glucose concentrations and glucose area under the curve) and insulin area under the curve appeared more consistent when exercise was performed during the postmeal period as compared with the premeal period; however, this observation was largely based on indirect comparisons between studies. Conclusions There is some evidence from randomized controlled trials that exercise performed 30 min after meal consumption may convey greater improvements in glycemic control for individuals with T2DM. However, there are only two studies that have directly assessed the role of exercise timing on glycemic management, and adopted methodologies are heterogeneous. Future low-risk trials in this field are warranted

Supplementary Material for: Influence of Hormonal Profile on Resting Metabolic Rate in Normal, Overweight and Obese Individuals

<b><i>Aims:</i></b> To investigate whether blood thyroid stimulating hormone (TSH), cortisol, insulin and glucose concentrations (plus glucose:insulin ratio; GIR) could improve the accuracy of resting metabolic rate (RMR) prediction in normal, overweight and obese persons. <b><i>Methods:</i></b> Predictive equations were developed and compared against indirect calorimetry measures for RMR in 217 weight-control clinic participants (n = 128 males and n = 89 females: ∼24% normal weight, ∼39% overweight and ∼37% obese). <b><i>Results:</i></b> Using the common accuracy criteria of the proportion of predicted RMR within ±10% of measured RMR, our equations (using age, height, weight and gender, plus the blood factors, both independently and in combination) were accurate ∼36-44% of the time, for the whole sample, and when separated by gender and weight class. Specifically, the addition of the blood hormone and glucose concentrations improved the accuracy of predicted RMR by only 1-8% (NS). <b><i>Conclusions:</i></b> Including blood TSH, cortisol, insulin, glucose and GIR into RMR prediction equations did not significantly improve estimation accuracy, which in any case only met a criterion of ±10% of the measured RMR ∼40% of the time. Further work to refine the prediction of RMR is still needed, and at present, direct measurements should be made wherever possible