The Effect of Timing of Exercise and Eating on Postprandial Response in Adults: A Systematic Review

Exercise Prescription for Postprandial Glycemic Management

The detrimental impacts of postprandial hyperglycemia on health are a critical concern, and exercise is recognized a pivotal tool in enhancing glycemic control after a meal. However, current exercise recommendations for managing postprandial glucose levels remain fairly broad and require deeper clarification. This review examines the existing literature aiming to offer a comprehensive guide for exercise prescription to optimize postprandial glycemic management. Specifically, it considers various exercise parameters (i.e., exercise timing, type, intensity, volume, pattern) for crafting exercise prescriptions. Findings predominantly indicate that moderate-intensity exercise initiated shortly after meals may substantially improve glucose response to a meal in healthy individuals and those with type 2 diabetes. Moreover, incorporating short activity breaks throughout the exercise session may provide additional benefits for reducing glucose response.

The effect of preprandial versus postprandial physical activity on glycaemia: Meta-analysis of human intervention studies

This meta-analysis aims to investigate the effect of preprandial physical activity (PA) versus postprandial PA on glycaemia in human intervention studies. Medline and Embase.com were searched until February 2023 for intervention studies in adults, directly comparing preprandial PA versus postprandial PA on glycaemia. Studies were screened using ASReview (34,837) and full texts were read by two independent reviewers (42 full text, 28 included). Results were analysed using pooled mean differences in random-effects models. Studies were either acute response studies (n = 21) or Randomized Controlled Trials (RCTs) over multiple weeks (n = 7). In acute response studies, postprandial outcomes followed the expected physiological patterns, and outcomes measured over 24 h showed no significant differences. For the RCTs, glucose area under the curve during a glucose tolerance test was slightly, but not significantly lower in preprandial PA vs postprandial PA (-0.29 [95 %CI:-0.66, 0.08] mmol/L, I2 = 64.36 %). Subgroup analyses (quality, health status, etc.) did not significantly change the outcomes. In conclusion, we found no differences between preprandial PA versus postprandial PA on glycaemia both after one PA bout as well as after multiple weeks of PA. The studies were of low to moderate quality of evidence as assessed by GRADE, showed contradictive results, included no long-term studies and used various designs and populations. We therefore need better RCTs, with more similar designs, in larger populations and longer follow-up periods (≥12 weeks) to have a final answer on the questions eat first, then exercise, or the reverse?

Temporal Dietary Pattern Cluster Membership Varies on Weekdays and Weekends but Both Link to Health

BACKGROUND

Energy and dietary quality are known to differ between weekdays and weekends. Data-driven approaches that incorporate time, amount, and duration of dietary intake have previously been used to partition participants' daily weekday dietary intake time series into clusters representing weekday temporal dietary patterns (TDPs) linked to health indicators in United States adults. Yet, neither the relationship of weekend day TDPs to health indicators nor how the TDP membership may change from weekday to weekend is known.

OBJECTIVES

This study was conducted to determine the association between TDPs on weekdays and weekend days and health indicators [diet quality, waist circumference (WC), body mass index (BMI), and obesity] and their overlap among participants.

METHODS

A weekday and weekend day 24-hour dietary recall of 9494 nonpregnant United States adults aged 20-65 years from the cross-sectional National Health and Nutrition Examination Survey 2007-2018 was used to determine the timing and amount of energy intake. Modified dynamic time warping and kernel k-means algorithm clustered participants into 4 TDPs on weekdays and weekend days. Multivariate regression models determined the associations between TDPs and health indicators, controlling for potential confounders and adjusting for the survey design and multiple comparisons. The percentages of overlap in cluster membership between TDPs on weekdays and weekend days were also determined.

RESULTS

United States adults with a TDP of evenly spaced, energy-balanced eating occasions, representing the TDP of more than one-third of all adults on weekdays and weekends, had significantly higher diet quality, lower BMI, WC, and odds of obesity when compared to those with other TDPs. Membership of most United States adults to TDPs varied from weekdays to weekends.

CONCLUSIONS

Both weekday and weekend TDPs were significantly associated with health indicators. TDP membership of most United States adults was not consistent on weekdays and weekends.

Clinical practice guidelines on physical activity and exercise for pregnant women with gestational diabetes mellitus: A systematic review

AIM

This review aimed to appraise clinical guidelines about exercise for women with gestational diabetes mellitus and summarize consensus and inconsistent recommendations.

BACKGROUND

Exercise is an effective non-pharmacological therapeutic for gestational diabetes mellitus, but the variety of relevant clinical practice guidelines is confusing for healthcare professionals.

DESIGN

This is a systematic review of clinical practice guidelines.

DATA SOURCES

Websites of guideline development institutions, eight literature databases and organizations of obstetricians, gynaecologists, midwives, and medical sports associations were searched for guidelines published from January 2011 to October 2021.

REVIEW METHODS

Two reviewers independently extracted recommendations. Four reviewers assessed guideline quality using the AGREE II instrument independently.

RESULTS

Fifteen guidelines were included. All women with diabetes are recommended to exercise during pregnancy. The consistent recommendations were for pre-exercise screening, for 30 min per exercise session on 5 days of the week or every day after meals, exercise at moderate intensity, using aerobic and resistance exercise, and walking. The main non-consistent recommendations included warning signs for women on insulin during exercise, minimum duration per session, intensity assessment, duration and frequency of sessions for strengthening and flexibility exercise and detailed physical activity giving birth.

CONCLUSIONS

Guidelines strongly support pregnant women with diabetes to exercise regularly. Research is needed to make non-consistent recommendations clear.

Temporal Patterns of Diet and Physical Activity and of Diet Alone Have More Numerous Relationships With Health and Disease Status Indicators Compared to Temporal Patterns of Physical Activity Alone

BACKGROUND

Daily temporal patterns of energy intake (temporal dietary patterns [TDPs]) and physical activity (temporal physical activity patterns [TPAPs]) have been independently and jointly (temporal dietary and physical activity patterns [TDPAPs]) associated with health and disease status indicators.

OBJECTIVE

The aim of this study was to compare the number and strength of association between clusters of daily TDPs, TPAPs, and TDPAPs and multiple health and disease status indicators.

DESIGN

This cross-sectional study used 1 reliable weekday dietary recall and 1 random weekday of accelerometer data to partition to create clusters of participants representing the 3 temporal patterns. Four clusters were created via kernel-k means clustering algorithm of the same constrained dynamic time warping distance computed over the time series for each temporal pattern.

PARTICIPANTS/SETTING

From the National Health and Nutrition Examination Survey (2003-2006), 1,836 US adults aged 20 through 65 years who were not pregnant and had valid diet, physical activity, sociodemographic, anthropometric, questionnaire, and health and disease status indicator data were included.

MAIN OUTCOME MEASURES

Health status indicators used as outcome measures were body mass index, waist circumference, fasting plasma glucose, hemoglobin A1c, triglycerides, high-density lipoprotein cholesterol, total cholesterol, and systolic and diastolic blood pressure; disease status indicators included obesity, type 2 diabetes mellitus, and metabolic syndrome.

STATISTICAL ANALYSES PERFORMED

Multivariate regression models determined associations between the clusters representing each pattern and health and disease status indicators, controlling for confounders and adjusting for multiple comparisons. The number of significant differences among clusters and adjusted R2 and Akaike information criterion compared the strength of associations between clusters of patterns and continuous and categorical health and disease status indicators.

RESULTS

TDPAPs showed 21 significant associations with health and disease status indicators, including body mass index, waist circumference, obesity, and type 2 diabetes; TDPs showed 19 significant associations; and TPAPs showed 8 significant associations.

CONCLUSIONS

TDPAPs and TDPs had stronger and more numerous associations with health and disease status indicators compared with TPAPs. Patterns representing the integration of daily dietary habits hold promise for early detection of obesity.

Interaction of exercise and meal timing on blood glucose concentrations

PURPOSE OF REVIEW

Exercise and diet are among the most studied behaviors that can affect blood glucose concentrations. Despite multiple studies examining these interventions in different populations and contexts, inconsistencies across studies have led to variable expectations. The purpose of this review is to more specifically examine how the timing of when exercise is performed in relation to meals can modify changes in glucose concentrations or insulin sensitivity. When possible, studies in type 2 diabetes are emphasized, but recent research in type 1 diabetes, obesity, and athletes is also considered.

RECENT FINDINGS

The effect of a single bout of exercise performed after an overnight fast is often comparable to that of postprandial exercise on 24 h mean glucose concentrations. However, there is recent evidence to suggest that in some situations, but not all, longer term metabolic adaptations can be more favorable when exercise is regularly performed in the fasted state.

SUMMARY

Exercise after an overnight fast can have different effects on glucose metabolism compared with postprandial exercise. The shorter term and longer term changes following fasting exercise can be relevant to those who are seeking greater glucoregulatory benefit from their exercise sessions, such as people with diabetes.

Continuous glucose monitoring in a healthy population: understanding the post-prandial glycemic response in individuals without diabetes mellitus

Continuous glucose monitoring has become a common adjunct in the management of Diabetes Mellitus. However, there has been a recent trend among individuals without diabetes using these devices as a means of monitoring their health. The increased visibility of glucose data has allowed users to study the effect lifestyle has upon post-prandial glucose levels. Although post-prandial hyperglycemia is well understood in the setting of diabetes, its impact in individuals without diabetes is less well defined. This article reviews the factors which contribute to post-prandial hyperglycemia in individuals without diabetes and how the data obtained from continuous glucose monitoring can be used to improve an individual's metabolic health.

Is There an Optimal Time of Day for Exercise? A Commentary on When to Exercise for People Living With Type 1 or Type 2 Diabetes

Exercise is a cornerstone of diabetes self-care because of its association with many health benefits. Several studies that have explored the best time of day to exercise to inform clinical recommendations have yielded mixed results. For example, for people with prediabetes or type 2 diabetes, there may be benefits to timing exercise to occur after meals, whereas people with type 1 diabetes may benefit from performing exercise earlier in the day. One common thread is the health benefits of consistent exercise, suggesting that the issue of exercise timing may be secondary to the goal of helping people with diabetes establish an exercise routine that best fits their life.

Using Continuous Glucose Monitoring to Prescribe a Time to Exercise for Individuals with Type 2 Diabetes

This study examines the potential utility of using continuous glucose monitoring (CGM) to prescribe an exercise time to target peak hyperglycaemia in people with type 2 diabetes (T2D). The main aim is to test the feasibility of prescribing an individualised daily exercise time, based on the time of CGM-derived peak glucose, for people with T2D. Thirty-five individuals with T2D (HbA1c: 7.2 ± 0.8%; age: 64 ± 7 y; BMI: 29.2 ± 5.2 kg/m²) were recruited and randomised to one of two 14 d exercise interventions: i) ExPeak (daily exercise starting 30 min before peak hyperglycaemia) or placebo active control NonPeak (daily exercise starting 90 min after peak hyperglycaemia). The time of peak hyperglycaemia was determined via a two-week baseline CGM. A CGM, accelerometer, and heart rate monitor were worn during the free-living interventions to objectively measure glycaemic control outcomes, moderate-to-vigorous intensity physical activity (MVPA), and exercise adherence for future translation in a clinical trial. Participation in MVPA increased 26% when an exercise time was prescribed compared to habitual baseline (p < 0.01), with no difference between intervention groups (p > 0.26). The total MVPA increased by 10 min/day during the intervention compared to the baseline (baseline: 23 ± 14 min/d vs. intervention: 33 ± 16 min/d, main effect of time p = 0.03, no interaction). The change in peak blood glucose (mmol/L) was similar between the ExPeak (-0.44 ± 1.6 mmol/L, d = 0.21) and the NonPeak (-0.39 ± 1.5 mmol/L, d = 0.16) intervention groups (p = 0.92). Prescribing an exercise time based on CGM may increase daily participation in physical activity in people with type 2 diabetes; however, further studies are needed to test the long-term impact of this approach.

Effects of accelerometry-derived physical activity energy expenditure on urinary C-peptide levels in a wild primate (Papio ursinus)

Animals have finite energy reserves for growth, survival, and reproduction and must maintain a stable energy balance. Measuring energy balance in the wild, however, is beset with methodological challenges. Quantification of urinary C-peptide (uCP), a proxy for insulin secretion, has enabled researchers to non-invasively estimate energy balance, and positive relationships between uCP levels and energy intake have been documented in numerous non-human primates. Comparatively few studies show that, consistent with insulin physiology, energy expenditure also alters levels of uCP. The timescale and extent of this relationship, however, remains unclear given the reliance on crude measures of activity and inferred energy expenditure. Here, for the first time, we test for effects of accelerometer-derived Vectorial Dynamic Body Acceleration (VeDBA) - a continuous measure of physical activity energy expenditure - on urinary C-peptide (uCP) levels in n = 12 wild chacma baboons (Papio ursinus). Applying a model selection approach, we show that VeDBA summed over short timescales (30 min to 1 h) prior to urine collection was negatively associated with uCP levels. Using the acceleration-based time individuals spent 'non-stationary' (i.e. locomoting) prior to urine collection as a predictor - instead of summed VeDBA - revealed similar but less clear results. Overall, the negative relationship between VeDBA and uCP levels highlights the importance of quantifying physical activity energy expenditure when using uCP measures to estimate energy balance and has potential implications for the field of energetics accelerometry.

After Dinner Rest a While, After Supper Walk a Mile? A Systematic Review with Meta-analysis on the Acute Postprandial Glycemic Response to Exercise Before and After Meal Ingestion in Healthy Subjects and Patients with Impaired Glucose Tolerance

BACKGROUND

The most effective way to cope with high blood sugar spikes is to engage in physical activity in temporal proximity to food intake. However, so far, it is unclear as to whether there is an optimal time for physical activity around food intake.

OBJECTIVES

We aimed to identify the impact of pre- and post-meal exercise on postprandial glucose excursions in humans with and without type 2 diabetes mellitus.

METHODS

We conducted a systematic review with meta-analysis, PROSPERO registration number: CRD42022324070. We screened MEDLINE/PubMed, Cochrane/CINAHL/EMBASE, and Web of Knowledge until 1 May, 2022. We used the risk of bias rating with the crossover extension of the Cochrane risk of bias assessment tool II. Standardized mean differences (SMDs, Hedges' g) with 95% confidence intervals (CIs) were calculated as pooled effect estimates of a random-effects meta-analysis. Eligibility criteria included three-armed randomized controlled trials comparing the acute effects of pre- and post-meal exercise to a no-exercise control in humans.

RESULTS

Eight randomized controlled trials (crossover trials, high risk of bias) with 30 interventions in 116 participants (47 diagnosed with type 2 diabetes, 69 without type 2 diabetes) were eligible. Exercise after meal ingestion (real food or meal replacement drinks) led to a reduction in postprandial glucose excursions compared with exercise before eating (15 effect sizes; SMD = 0.47 [95% CI 0.23, 0.70]) and an inactive control condition (15 effect sizes; SMD = 0.55 [95% CI 0.34, 0.75]. Pre-meal exercise did not lead to significantly lower postprandial glucose compared to an inactive control (15 effect sizes; SMD =  - 0.13 [95% CI - 0.42, 0.17]). The time between meal and exercise (estimate =  - 0.0151; standard error = 0.00473; Z =  - 3.19; p = 0.001; 95% CI - 0.024, - 0.006) had a moderating influence on postprandial glucose excursions.

CONCLUSIONS

Exercise, i.e., walking, has a greater acute beneficial impact on postprandial hyperglycemia when undertaken as soon as possible after a meal rather than after a longer interval or before eating.

CLINICAL TRIAL REGISTRATION

The review was pre-registered in the PROSPERO database (CRD42022324070). The date of submission was 07.04.2022, with the registration on 08.05.2022.

Joint Temporal Patterns By Integrating Diet and Physical Activity

Both diet and physical activity are associated with obesity and chronic diseases such as diabetes and metabolic syndrome. Early efforts in connecting dietary and physical activity behaviors to generate patterns rarely considered the use of time. In this paper, we propose a distance-based cluster analysis approach to find joint temporal diet and physical activity patterns among U.S. adults ages 20-65. Dynamic Time Warping (DTW) generalized to multi-dimensions is combined with commonly used clustering methods to generate unbiased partitioning of the National Health and Nutrition Examination Survey 2003-2006 (NHANES) dataset. The clustering results are evaluated using visualization of the clusters, the Silhouette Index, and the associations between clusters and health status indicators based on multivariate regression models. Our experiments indicate that the integration of diet, physical activity, and time has the potential to discover joint temporal patterns with association to health.

Short-term removal of exercise impairs glycemic control in older adults: A randomized trial

Postprandial glycemia (PPG) predicts cardiovascular disease, and short-term physical inactivity increases PPG in young, active adults. Whether this occurs in older, active adults who may be more prone to bouts of inactivity is unknown. This study determined if postprandial interstitial glucose (PPIG) was impaired in active older adults following the removal of exercise for 3 days (NOEX) compared to active young adults. In this randomized, crossover study, 11 older (69.1 ± 1.9 years) and 9 young (32.8 ± 1.8 years) habitually active (≥90 min/week of exercise) adults completed 3-days of NOEX and 3-days of normal habitual exercise (EX), separated by ≥1 week. Diet was standardized across phases. Glycemic control (3-day average) was assessed via continuous glucose monitoring during both phases. Significant main effects of age and phase were detected (p < 0.05), but no interaction was found for steps/day (p > 0.05) (old EX: 6283 ± 607, old NOEX: 2380 ± 382 and young EX: 8798 ± 623, young NOEX: 4075 ± 516 steps/day). Significant main effects of age (p = 0.002) and time (p < 0.001) existed for 1-h PPIG, but no effect of phase or interactions was found (p > 0.05). Significant main effects (p < 0.05) of age (old: 114 ± 1 mg/dl, young: 106 ± 1 mg/dl), phase (NOEX: 112 ± 1 mg/dl, EX: 108 ± 1 mg/dl), and time (0 min: 100 ± 2, 30 min: 118 ± 2, 60 min: 116 ± 2, 90 min: 111 ± 2, 120 min: 108 ± 2 mg/dl) in 2-h PPIG were detected, but no interaction was found (p > 0.05). However, only significant main effects of phase (NOEX: 14 ± 1 and EX:12 ± 1, p > 0.05) were found for 24-h blood glucose standard deviation. Older adults appear to have impaired glycemic control compared to young adults and exercise removal impairs glycemic control in both populations. Yet, the impairment in glycemic control with exercise removal is not different between old and young adults.

Walking Attenuates Postprandial Glycemic Response: What Else Can We Do without Leaving Home or the Office?

We evaluated the effects of different exercise types suitable for a home/work setting on the postprandial glucose response. Twenty-three healthy, active, young individuals performed one of two studies (12 in Study 1 and 11 in Study 2), with four randomized protocols each. After a meal high in carbohydrate content (1 g of carbohydrate per kg of body weight), in Study 1, participants performed 30 min of either walking (WALK), bench stepping exercise (STEP) or isometric wall squat (SQUAT); in Study 2, participants performed 30 min of either walking (WALK), neuromuscular electrical stimulation alone (P_NMES) or superimposed on voluntary muscle contraction (VC_NMES). In both studies, participants performed a prolonged sitting condition (CON) that was compared to the exercise sessions. In Study 1, WALK and STEP significantly reduced the glucose peak compared to CON (p < 0.011). In Study 2, the peak was significantly reduced in WALK compared to CON, P_NMES and VC_NMES (p < 0.011) and in VC_NMES compared to CON and P_NMES (p < 0.011). A significant reduction of 3 h glucose iAUC was found for WALK and VC_NMES compared to CON and P_NMES (p < 0.033). In conclusion, WALK is the most effective strategy for improving the postprandial glycemic response. However, STEP and VC_NMES can also be used for reducing postprandial glycemia.

Differences in Dietary Intake Exist among U.S. Adults by Diabetic Status Using NHANES 2009–2016

The objective was to determine the most frequently consumed food items, food subcategories, and food categories, and those that contributed most to total energy intake for the group of U.S. adults reporting taking insulin, those with type 2 diabetes (T2D) not taking insulin, and those without diabetes. Laboratory tests and questionnaires of the National Health and Nutrition Examination Survey 2009–2016 classified 774 participants reporting taking insulin, 2758 participants reporting T2D not taking insulin, and 17,796 participants without diabetes. Raw and weighted frequency and energy contributions of each food item, food subcategory, and food category were calculated and ranked. Comparisons among groups by broad food category used the Rao–Scott modified chi-square test. Soft drinks ranked as the 8th and 6th most consumed food subcategory of participants with T2D not taking insulin and those without diabetes, and contributed 5th and 2nd most to energy, respectively. The group reporting taking insulin is likely to consume more protein foods and less soft drink compared to the other two groups. Lists of the most frequently reported foods and foods contributing most to energy may be helpful for nutrition education, prescribing diets, and digital-based dietary assessment for the group reporting taking insulin.

Timing of physical activity within the 24-hour day and its influence on health: a systematic review

BACKGROUND

Recent studies report that the health benefits of physical activity differ depending on whether the activity is performed in the morning, afternoon or evening. The purpose of this systematic review was to examine whether the timing of physical activity within the 24-hour day is associated with health.

METHODS

Five databases were searched for English or French language peer-reviewed studies that examined whether the timing of physical activity within the day is associated with health. No limits were placed on publication year, study population, study design or health outcomes. Studies that examined acute effects of physical activity or timing of physical activity around food intake were excluded.

RESULTS

This systematic review examined 35 studies, with 17 259 participants, and the following health outcomes: measures of sleep health, adiposity, fat-free mass and muscle size, cardiometabolic biomarkers, physical function and mobility, mental health, and risk of cardiovascular disease, cancer, and mortality. Heterogeneity across studies precluded meta-analyses, and we present our findings using narrative syntheses. Of the 35 studies, 11 reported that morning physical activity provides greater health benefits than afternoon/ evening physical activity, while 12 found that morning physical activity provides fewer health benefits than afternoon/evening physical. In the remaining 12 studies, there was no clear difference in health benefits based on the timing of physical activity. The quality of evidence for the different health outcomes across study designs was very low.

CONCLUSION

There is no consistent evidence that physical activity at one time of day provides more favourable health benefits than physical activity at a different time of day. (PROSPERO registration no.: CRD42021231088).

Personalising activity to target peak hyperglycaemia and improve cardiometabolic health in people with type 2 diabetes: protocol for a randomised controlled trial

INTRODUCTION

The benefits of physical activity for glycaemic control in type 2 diabetes (T2D) are well-known. However, whether established glycaemic and cardiovascular benefits can be maximised by exercising at a certain time of day is unknown. Given postprandial glucose peaks contribute to worsening glycated haemoglobin (HbA1c) and cardiovascular risk factors, and that exercise immediately lowers blood glucose, prescribing exercise at a specific time of day to attenuate peak hyperglycaemia may improve glycaemic control and reduce the burden of cardiovascular disease in people with T2D.

METHODS AND ANALYSIS

A single-centre randomised controlled trial will be conducted by the University of Wollongong, Australia. Individuals with T2D (n=70, aged 40-75 years, body mass index (BMI): 27-40 kg/m²) will be recruited and randomly allocated (1:1), stratified for sex and insulin, to one of three groups: (1) exercise at time of peak hyperglycaemia (ExPeak, personalised), (2) exercise not at time of peak hyperglycaemia (NonPeak) or (3) waitlist control (WLC, standard care). The trial will be 5 months, comprising an 8-week intervention and 3-month follow-up. Primary outcome is the change in HbA1c preintervention to postintervention. Secondary outcomes include vascular function (endothelial function and arterial stiffness), metabolic control (blood lipids and inflammation) and body composition (anthropometrics and dual-energy X-ray absorptiometry (DEXA)). Tertiary outcomes will examine adherence.

ETHICS AND DISSEMINATION

The joint UOW and ISLHD Ethics Committee approved protocol (2019/ETH09856) prospectively registered at the Australian New Zealand Clinical Trials Registry. Written informed consent will be obtained from all eligible individuals prior to commencement of the trial. Study results will be published as peer-reviewed articles, presented at national/international conferences and media reports.

TRIAL REGISTRATION NUMBER

ACTRN12619001049167.

Continuous Glucose Monitoring in Healthy Adults—Possible Applications in Health Care, Wellness, and Sports

Introduction: Continuous glucose monitoring (CGM) systems were primarily developed for patients with diabetes mellitus. However, these systems are increasingly being used by individuals who do not have diabetes mellitus. This mini review describes possible applications of CGM systems in healthy adults in health care, wellness, and sports. Results: CGM systems can be used for early detection of abnormal glucose regulation. Learning from CGM data how the intake of foods with different glycemic loads and physical activity affect glucose responses can be helpful in improving nutritional and/or physical activity behavior. Furthermore, states of stress that affect glucose dynamics could be made visible. Physical performance and/or regeneration can be improved as CGM systems can provide information on glucose values and dynamics that may help optimize nutritional strategies pre-, during, and post-exercise. Conclusions: CGM has a high potential for health benefits and self-optimization. More scientific studies are needed to improve the interpretation of CGM data. The interaction with other wearables and combined data collection and analysis in one single device would contribute to developing more precise recommendations for users.

The Effects of Postprandial Walking on the Glucose Response after Meals with Different Characteristics

We evaluated the effect of postprandial walking on the post-meal glycemic response after meals with different characteristics. Twenty-one healthy young volunteers participated in one of two randomized repeated measures studies. Study 1 (10 participants) assessed the effects of 30 min of brisk walking after meals with different carbohydrate (CHO) content (0.75 or 1.5 g of CHO per kg/body weight). Study 2 (11 participants) evaluated the effects of 30 min of brisk walking after consuming a mixed meal or a CHO drink matched for absolute CHO content (75 g). Postprandial brisk walking substantially reduced (p < 0.009) the glucose peak in both studies, with no significant differences across conditions. When evaluating the glycemic response throughout the two hours post-meal, postprandial walking was more effective after consuming a lower CHO content (Study 1), and similarly effective after a mixed meal or a CHO drink (Study 2), although higher glucose values were observed when consuming the CHO drink. Our findings show that a 30 min postprandial brisk walking session improves the glycemic response after meals with different CHO content and macronutrient composition, with implications for postprandial exercise prescription in daily life scenarios.

Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance

As years progress, we are found more often in a postprandial than a postabsorptive state. Chrononutrition is an integral part of metabolism, pancreatic function, and hormone secretion. Eating most calories and carbohydrates at lunch time and early afternoon, avoiding late evening dinner, and keeping consistent number of daily meals and relative times of eating occasions seem to play a pivotal role for postprandial glycemia and insulin sensitivity. Sequence of meals and nutrients also play a significant role, as foods of low density such as vegetables, salads, or soups consumed first, followed by protein and then by starchy foods lead to ameliorated glycemic and insulin responses. There are several dietary schemes available, such as intermittent fasting regimes, which may improve glycemic and insulin responses. Weight loss is important for the treatment of insulin resistance, and it can be achieved by many approaches, such as low-fat, low-carbohydrate, Mediterranean-style diets, etc. Lifestyle interventions with small weight loss (7–10%), 150 min of weekly moderate intensity exercise and behavioral therapy approach can be highly effective in preventing and treating type 2 diabetes. Similarly, decreasing carbohydrates in meals also improves significantly glycemic and insulin responses, but the extent of this reduction should be individualized, patient-centered, and monitored. Alternative foods or ingredients, such as vinegar, yogurt, whey protein, peanuts and tree nuts should also be considered in ameliorating postprandial hyperglycemia and insulin resistance. This review aims to describe the available evidence about the effects of diet, chrononutrition, alternative dietary interventions and exercise on postprandial glycemia and insulin resistance.

Joint temporal dietary and physical activity patterns: associations with health status indicators and chronic diseases

BACKGROUND

Diet and physical activity (PA) are independent risk factors for obesity and chronic diseases including type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS). The temporal sequence of these exposures may be used to create patterns with relations to health status indicators.

OBJECTIVES

The objectives were to create clusters of joint temporal dietary and PA patterns (JTDPAPs) and to determine their association with health status indicators including BMI, waist circumference (WC), fasting plasma glucose, glycated hemoglobin, triglycerides, HDL cholesterol, total cholesterol, blood pressure, and disease status including obesity, T2DM, and MetS in US adults.

METHODS

A 24-h dietary recall and random day of accelerometer data of 1836 participants from the cross-sectional NHANES 2003-2006 data were used to create JTDPAP clusters by constrained dynamic time warping, coupled with a kernel k-means clustering algorithm. Multivariate regression models determined associations between the 4 JTDPAP clusters and health and disease status indicators, controlling for potential confounders and adjusting for multiple comparisons.

RESULTS

A JTDPAP cluster with proportionally equivalent energy consumed at 2 main eating occasions reaching ≤1600 and ≤2200 kcal from 11:00 to 13:00 and from 17:00 to 20:00, respectively, and the highest PA counts among 4 clusters from 08:00 to 20:00, was associated with significantly lower BMI (P < 0.0001), WC (P = 0.0001), total cholesterol (P = 0.02), and odds of obesity (OR: 0.2; 95% CI: 0.1, 0.5) than a JTDPAP cluster with proportionally equivalent energy consumed reaching ≤1600 and ≤1800 kcal from 11:00 to 14:00 and from 17:00 to 21:00, respectively, and high PA counts from 09:00 to 12:00.

CONCLUSIONS

The joint temporally patterned sequence of diet and PA can be used to cluster individuals with meaningful associations to BMI, WC, total cholesterol, and obesity. Temporal patterns hold promise for future development of lifestyle patterns that integrate additional temporal and contextual activities.

Postprandial Metabolism and Physical Activity in Asians: A Narrative Review

The widespread benefits of physical activity in enhancing health and lowering the risk of non-communicable chronic diseases are well established across populations globally. Nevertheless, the prevalence of several lifestyle-related chronic diseases, including cardiovascular disease, varies markedly across countries and ethnicities. Direct ethnic comparative studies on the health benefits of physical activity are sparse and evidence-based physical activity guidelines are not ethnicity-specific. Indeed, physical activity guidelines in some Asian countries were developed primarily based on data from Western populations even though the magnitude of potential benefit may not be the same among different ethnic groups. Unfavorable diurnal perturbations in postprandial triglycerides and glucose are risk factors for cardiovascular disease. This narrative review summarizes differences in these risk factors primarily between individuals of Asian and white European descent but also within different Asian groups. Moreover, the variable effects of physical activity on mitigating risk factors among these ethnic groups are highlighted along with the underlying metabolic and hormonal factors that potentially account for these differences. Future ethnic comparative studies should include investigations in understudied ethnic groups, such as those of East Asian origin, given that the effectiveness of physical activity for ameliorating cardiovascular disease varies even among Asian groups.

Exercise-nutrient interactions for improved postprandial glycemic control and insulin sensitivity

Type 2 diabetes (T2D) is a rapidly growing yet largely preventable chronic disease. Exaggerated increases in blood glucose concentration following meals is a primary contributor to many long-term complications of the disease that decrease quality of life and reduce lifespan. Adverse health consequences also manifest years prior to the development of T2D due to underlying insulin resistance and exaggerated postprandial concentrations of the glucose-lowering hormone insulin. Postprandial hyperglycemic and hyperinsulinemic excursions can be improved by exercise, which contributes to the well-established benefits of physical activity for the prevention and treatment of T2D. The aim of this review is to describe the postprandial dysmetabolism that occurs in individuals at risk for and with T2D, and highlight how acute and chronic exercise can lower postprandial glucose and insulin excursions. In addition to describing the effects of traditional moderate-intensity continuous exercise on glycemic control, we highlight other forms of activity including low-intensity walking, high-intensity interval exercise, and resistance training. In an effort to improve knowledge translation and implementation of exercise for maximal glycemic benefits, we also describe how timing of exercise around meals and post-exercise nutrition can modify acute and chronic effects of exercise on glycemic control and insulin sensitivity. Novelty: Exaggerated postprandial blood glucose and insulin excursions are associated with disease risk. Both a single session and repeated sessions of exercise improve postprandial glycemic control in individuals with and without T2D. The glycemic benefits of exercise can be enhanced by considering the timing and macronutrient composition of meals around exercise.

How do we support walking prescriptions for type 2 diabetes management? Facilitators and barriers following a 3-month prescription

INTRODUCTION Prescribing physical activity is an inexpensive method to promote patients' long-term health, but determinants of adherence with physical activity prescriptions are seldom considered. AIM To identify facilitators and barriers experienced by adults with type 2 diabetes when prescribed regular walking. METHODS Participants were prescribed a regular walking routine that met current physical activity guidelines for type 2 diabetes management for a period of 3 months. Pre- and post-intervention questions considered participants' self-rated health and physical activity amount. Thematic analysis of recorded interviews held after the 3-month prescription identified barriers and facilitators to adherence for participants. RESULTS Twenty-eight adults (aged 60±9 years, body mass index 32.3±4.0kg/m2, HbA1c 59±16mmol/mol) participated in the 3-month intervention, providing 7 years of lived experience. Self-rated health (14%; 95% confidence interval (CI) 7-22%) and time spent walking (+11 min/day; 95% CI 4-18 min/day) increased following the prescription. Major themes motivating participants were: establishing a walking routine; the support of their family members; observing health benefits; and being monitored by a health professional. The greatest barriers were associated with walking in the evening and included feelings of insecurity in the dark or a preference for sedentary behaviour. DISCUSSION A prescription to walk increased time spent in physical activity and self-rated health in adults with type 2 diabetes. Health-care professionals can support walking prescriptions by promoting facilitators and reducing barriers to prescription adherence. Practical solutions to barriers include identifying alternative physical activity opportunities within the house or advice to develop support networks to provide company while walking.

Expanding the Capabilities of Nutrition Research and Health Promotion Through Mobile-Based Applications

Mobile-based applications are popular and prevalently used in the US population. Applications focusing on nutrition offer platforms for quantifying and changing behaviors to improve dietary intake. Such behavior changes can intervene in the relation of diet to promote health and prevent disease. Mobile applications offer a safe and convenient way to collect user data and share it back to users, researchers, and to health care providers. Other lifestyle factors like activity, sleep, and sedentary behavior, can also be quantified and included in investigations of how lifestyle is related to health. Yet, challenges in the assessment offered through mobile applications and effectiveness to change behavior still remain, including rigorous evaluation, demonstration of successful health improvement, and participant engagement. The data mobile applications generate, however, expands opportunities for discovery of the integrated and time-based nature of various daily activities in relation to health. This article is a summary of a symposium at Nutrition 2020 Live Online on the role of mobile applications as a tool for nutrition research and health promotion. The types and capabilities of mobile applications, challenges in their evaluation and use in research, and opportunities for the data they generate along with a specific example, are reviewed.

Effect of a single bout of morning or afternoon exercise on glucose fluctuation in young healthy men

The timing of exercise plays an important role in the effect of the exercise on physiological functions, such as substrate oxidation and circadian rhythm. Exercise exerts different effects on the glycemic response to exercise and meal intake depending on when the exercise performed. Here, we comprehensively investigated the effects of the timing (morning or afternoon) of exercise on glucose fluctuation on the basis of several indices: glycemic variability over 24 h (24-h SD), J-index, mean amplitude of glucose excursions (MAGE), continuous overall net glycemic action (CONGA), and detrended fluctuation analysis (DFA). Eleven young men participated in 3 trials in a repeated measures design in which they performed a single bout of exercise at 60% of their maximal oxygen uptake for 1 h beginning either at 7:00 (morning exercise), 16:00 (afternoon exercise), or no exercise (control). Glucose levels were measured using a continuous glucose monitoring system (CGMs). Glucose fluctuation was slightly less stable when exercise was performed in the afternoon than in the morning, indicated by higher CONGA at 2 h and α₂ in DFA in the afternoon exercise trial than in the control trial. Additionally, decreased stability in glucose fluctuation in the afternoon exercise trial was supported by the descending values of the other glucose fluctuation indices in order from the afternoon exercise, morning exercise, and control trials. Meal tolerance following exercise was decreased after both exercise trials. Glucose levels during exercise were decreased only in the afternoon exercise trial, resulting in less stable glucose fluctuations over 24 h.

The Effect of Different Postprandial Exercise Types on Glucose Response to Breakfast in Individuals with Type 2 Diabetes

Postprandial exercise represents an important tool for improving the glycemic response to a meal. This study evaluates the effects of the combination and sequence of different exercise types on the postprandial glycemic response in patients with type 2 diabetes. In this repeated-measures crossover study, eight patients with type 2 diabetes performed five experimental conditions in a randomized order: (i) uninterrupted sitting (CON); (ii) 30 min of moderate intensity aerobic exercise (walking) (A); (iii) 30 min of combined aerobic and resistance exercise (AR); (iv) 30 min of combined resistance and aerobic exercise (RA); and (v) 15 min of resistance exercise (R). All the exercise sessions started 30 min after the beginning of a standardized breakfast. All the exercise conditions showed a significant attenuation of the post-meal glycemic excursion (P < 0.003) and the glucose incremental area under the curve at 0–120 min (P < 0.028) and 0–180 min (P < 0.048) compared with CON. A greater reduction in the glycemic peak was observed in A and AR compared to RA (P < 0.02). All the exercise types improved the post-meal glycemic response in patients with type 2 diabetes, with greater benefits when walking was performed alone or before resistance exercise.

Walking Initiated 20 Minutes before the Time of Individual Postprandial Glucose Peak Reduces the Glucose Response in Young Men with Overweight or Obesity: A Randomized Crossover Study

BACKGROUND

Although a single bout of postmeal exercise can lower postprandial glucose (PPG), its optimal timing remains unclear.

OBJECTIVE

This study aimed to investigate the effect of exercise timing using an individualized approach on PPG in overweight or obese young men.

METHODS

Twenty men [age: 23.0 ± 4.3 y; BMI (kg/m2): 27.4 ± 2.8] each completed three 240-min trials in a randomized order separated by 6-14 d: 1) sitting (SIT), 2) walking initiated at each participant's PPG-peak time (PPGP) (iP), and 3) walking initiated 20 min before the PPGP (20iP). For each participant, PPGP was predetermined using continuous glucose monitoring. Walking was performed at 50% maximal oxygen consumption for 30 min. Venous blood was collected at 15- and 30-min intervals for 0-120 min and 120-240 min, respectively. The primary outcome was plasma PPG. Generalized estimating equations were used for comparison between trials.

RESULTS

Compared with SIT, the 4-h incremental AUCs (iAUCs) for plasma PPG (-0.6 mmol · L-1 · h; P = 0.047) and insulin (-28.7%, P < 0.001) were reduced in 20iP only, and C-peptide concentrations were lower after iP (-14.9%, P = 0.001) and 20iP (-28.7%, P < 0.001). Plasma insulin (-11.1%, P = 0.006) and C-peptide (-8.3%, P = 0.012) were lower due to the 20iP compared with iP treatment. Finally, PPG reductions due to iP and 20iP occurred only in men with a BMI > 27.5 kg/m2 (iP, -11.2%; 20iP, -14.7%; P = 0.047) and higher glucose iAUC values during SIT (iP, -25.5%; 20iP, -25.7%; P < 0.001).

CONCLUSIONS

Walking initiated 20 min before PPGP lowered PPG and plasma insulin and C-peptide concentrations in young men with overweight or obesity, in particular in those with high BMI or glucose iAUC values during SIT; it also lowered plasma insulin and C-peptide concentrations more effectively than did exercise initiated at PPGP. This trial was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx) as ChiCTR1900023175.

Effects of Different Exercise Strategies to Improve Postprandial Glycemia in Healthy Individuals

PURPOSE

We systematically investigated the effects of different exercise strategies on postprandial glycemia.

METHODS

Six randomized repeated-measures crossover studies were performed. Study 1 compared the effects of 60 min of brisk walking started at 30, 60, or 90 min after breakfast on postbreakfast and postlunch glycemic responses. Study 2 investigated the effects of 30 min of different exercise types (aerobic vs resistance vs combined). Study 3 compared the effects of 30 min of different aerobic exercise types (walking vs cycling vs elliptical). Study 4 evaluated the effects of 30 min of brisk walking performed 45 min before or 15 and 30 min after breakfast. Study 5 compared 30 with 45 min of postprandial brisk walking. Study 6 compared the effects of a total of 30 min brisk walking exercise fragmented in bouts of 15, 5, or 2.5 min performed every 15 min.

RESULTS

Postprandial but not preprandial exercise improved glycemic response (studies 1 and 4). The glycemic peak was attenuated only when exercise started 15 min after the meal (study 4). A similar reduction of the postprandial glycemic response was observed with different exercise types (studies 2 and 3). Thirty and 45 min of brisk walking provided a similar reduction of the postprandial glucose response (study 5). When performing activity breaks, 10 and 20 min of cumulative exercise were sufficient to attenuate postprandial glycemia in the first hour postmeal (study 6).

CONCLUSION

Our findings provide insight into how to choose timing, type, duration, and modality for postprandial exercise prescription in healthy individuals.

Accumulating Physical Activity in Short or Brief Bouts for Glycemic Control in Adults With Prediabetes and Diabetes

Clinical practice guidelines on physical activity and diabetes currently stipulate physical activity can be accumulated in bouts of ≥10 minutes to meet recommendations for health benefits. Individuals are also encouraged to interrupt prolonged sitting with brief activity breaks of ∼1 to 5 minutes in duration. Growing research highlights accumulating activity in shorter bouts across the day as a potential strategy to improve glycemic control and to help those who are largely sedentary meet physical activity guidelines. Research has shown favourable glycemic benefits for postprandial glucose and glycated hemoglobin with either 3 short (10 to 15 minutes) or frequent brief (1 to 5 minutes) bouts of activity spread around meals or throughout the day. To date, most studies examining accumulated activity were done with people with type 2 diabetes compared with sedentary conditions, were short term and measured various indices of glycemic control using continuous glucose monitoring. The 7 trials comparing accumulating 3 short bouts to a single bout showed comparable benefits for glycemic control (i.e. fasting glucose, 24 h mean glucose and postprandial hyperglycemia). Furthermore, timing short bouts around meals may improve postprandial glucose and hyperglycemia more than a single bout. It is unknown whether a threshold for the duration of accumulated bouts exists---that is, "how much is enough?" In this narrative review, we focus on the glycemic effects of physical activity accumulated in short or brief bouts for people with prediabetes and diabetes as compared with a single continuous bout. Given that poor adherence to physical activity recommendations and that fewer opportunities exist in modern societies for incidental (nonexercise) physical activity, accumulating activity may be a choice strategy for improving glycemic control in those with and at risk of diabetes.

Correction: Marah Aqeel et al. "The Effect of Timing of Exercise and Eating on Postprandial Response in Adults: A Systematic Review". Nutrients 2020, 12, 221

In the original paper, the total number of included studies was n = 20 and is n = 17 in the revised version. Also, in the original paper, the total number of participants was n = 352, while it is n = 332 in the revised paper.