Adipose Tissue Responses to Breaking Sitting in Men and Women with Central Adiposity

Effects of acute and chronic stair-climbing exercise on metabolic health: A systematic review

Stair climbing exercise (SE) provides a feasible approach to elevate physical activity, but the effects on metabolic health are unclear. We systematically reviewed the currently available evidence on the effects of SE on fasting and postprandial glycaemia and lipidaemia. Studies were included if they investigated the effects of acute or chronic (at least 2 weeks) SE on fasting and/or postprandial glycaemic (insulin and glucose) and lipidaemic (triacylglycerols and non-esterified fatty acids) responses in healthy, prediabetic or type 2 diabetic adult populations. PubMed, Web of Science and Scopus were searched for eligible studies until July 2022. A total of 25 studies (14 acute and 11 chronic) were eligible for review. Acute bout(s) of SE can reduce postprandial glycaemia in individuals with prediabetes and type 2 diabetes (8 of 9 studies), but not in normoglycemic individuals. The effects of acute SE on postprandial lipidaemic responses and SE training on both fasting and postprandial glycaemia/lipidaemia were unclear. Acute SE may reduce postprandial glucose concentrations in people with impaired glycaemic control, but high-quality studies are needed. More studies are needed to determine the effect of chronic SE training on postprandial glucose and lipid responses, and the acute effects of SE on lipid responses.

Breaking prolonged sitting increases 24-h physical activity and self-perceived energy levels but does not acutely affect cognition in healthy adults

INTRODUCTION

It is unknown whether predetermined (un)interrupted sitting within a laboratory setting will induce compensatory changes in human behaviours (energy intake and physical activity) once people return to a free-living environment. The effects of breaking up prolonged sitting on cognition are also unclear.

METHODS

Twenty-four (male = 13) healthy participants [age 31 ± 8 y, BMI 22.7 ± 2.3 kg/m2 (mean ± SD)] completed 320 min mixed-feeding trials under prolonged sitting (SIT) or with 2 min walking at 6.4 km/h every 20 min (ACTIVE), in a randomised crossover design. Human behaviours were recorded post-trial under free-living conditions until midnight. Cognitive performance was evaluated before and immediately after SIT and ACTIVE trials. Self-perceived sensations (appetite, energy and mood) and finger prick blood glucose levels were collected at regular intervals throughout the trials.

RESULTS

There were no differences between trials in eating behaviour and spontaneous physical activity (both, p > 0.05) in free-living conditions, resulting in greater overall total step counts [11,680 (10740,12620) versus 6049 (4845,7253) steps] and physical activity energy expenditure (PAEE) over 24-h period in ACTIVE compared to SIT (all, p < 0.05). Greater self-perceived levels of energy and lower blood glucose iAUC were found in ACTIVE trial compared to SIT trial (both, p < 0.05). No differences were found in cognitive performance between trials (all, p > 0.05).

CONCLUSION

Breaking up sitting does not elicit subsequent behavioural compensation, resulting in greater 24-h step counts and PAEE in healthy adults. Breaking up sitting reduces postprandial glucose concentrations and elicits greater self-perceived energy levels, but these positive effects do not acutely translate into improved cognitive function.

Imprecision nutrition? Duplicate meals result in unreliable individual glycemic responses measured by continuous glucose monitors across four dietary patterns in adults without diabetes

Background

Continuous glucose monitors (CGMs) are being used to characterize postprandial glycemic responses and thereby provide personalized dietary advice to minimize glycemic excursions. However, the efficacy of such advice depends on reliable CGM responses.

Objective

To explore within-subject variability of CGM responses to duplicate meals in an inpatient setting.

Methods

CGM data were collected in two controlled feeding studies (NCT03407053 and NCT03878108) in 30 participants without diabetes capturing 1056 meal responses in duplicate ~1 week apart from four dietary patterns. One study used two different CGMs (Abbott Freestyle Libre Pro and Dexcom G4 Platinum) whereas the other study used only Dexcom. We calculated the incremental area under the curve (iAUC) for each 2-h post-meal period and compared within-subject iAUCs using the same CGM for the duplicate meals using linear correlations, intra-class correlation coefficients (ICC), Bland-Altman analyses, and compared individual variability of glycemic responses to duplicate meals versus different meals using standard deviations (SDs).

Results

There were weak to moderate positive linear correlations between within- subject iAUCs for duplicate meals (Abbott r=0.47, p<0.0001, Dexcom r=0.43, p<0.0001), with low within-participant reliability indicated by ICC (Abbott 0.31, Dexcom 0.14). Bland-Altman analyses indicated wide limits of agreement (Abbott -31.3 to 31.5 mg/dL, Dexcom -30.8 to 30.4 mg/dL) but no significant bias of mean iAUCs for duplicate meals (Abbott 0.1 mg/dL, Dexcom -0.2 mg/dL). Individual variability of glycemic responses to duplicate meals was similar to that of different meals evaluated each diet week for both Abbott (SDduplicate = 10.7 mg/dL , SDweek 1 =12.4 mg/dL, SDweek 2 =11.6 mg/dL, p=0.38) and Dexcom (SDduplicate = 11.1 mg/dL, SDweek 1 = 11.5 mg/dL, SDweek 2 =11.9 mg/dL, p=0.60).

Conclusions

Individual postprandial CGM responses to duplicate meals were unreliable in adults without diabetes. Personalized diet advice based on CGM measurements in adults without diabetes requires more reliable methods involving aggregated repeated measurements.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

Breaking Up Prolonged Sitting to Improve Cardiometabolic Risk: Dose-Response Analysis of a Randomized Crossover Trial

PURPOSE

Sedentary time is ubiquitous in developed nations and is associated with deleterious health outcomes. Physical activity guidelines recommend reductions in sedentary time; however, quantitative guidelines that inform how often and how long sedentary time should be interrupted have not been provided. The purpose of this study was to examine the acute effects of multiple doses of a sedentary break intervention on cardiometabolic risk factors, concurrently evaluating efficacy of varying frequencies and durations of sedentary breaks.

METHODS

In a randomized crossover study, middle- and older-age adults ( n = 11) completed the following 8-h conditions on five separate days: 1 uninterrupted sedentary (control) condition and four acute (experimental) trials that entailed different sedentary break frequency/duration combinations: every 30 min for 1 min, every 30 min for 5 min, every 60 min for 1 min, and every 60 min for 5 min. Sedentary breaks entailed light-intensity walking. Glucose and blood pressure (BP) were measured every 15 and 60 min, respectively.

RESULTS

Compared with control, glucose incremental area under the curve was significantly attenuated only for the every 30 min for 5-min dose (-11.8[4.7]; P = 0.017). All sedentary break doses yielded significant net decreases in systolic BP from baseline compared with control ( P < 0.05). The largest reductions in systolic BP were observed for the every 60 min for 1 min (-5.2 [1.4] mm Hg) and every 30 min for 5 min (-4.3[1.4] mm Hg) doses.

CONCLUSIONS

The present study provides important information concerning efficacious sedentary break doses. Higher-frequency and longer-duration breaks (every 30 min for 5 min) should be considered when targeting glycemic responses, whereas lower doses may be sufficient for BP lowering.

Dose-response effects of periodic physical activity breaks on the chronic inflammatory risk associated with sedentary behavior in high- and upper-middle income countries: A systematic review and meta-analysis

BACKGROUND AND AIMS

Though moderate-vigorous physical activity (MVPA) is speculated to mitigate the inflammatory risk associated with sedentary behavior, only a fraction of the global population meets the recommended weekly dose of MVPA. More individuals indulge in bouted and sporadic light-intensity physical activity (LIPA) that occurs throughout the typical day. However, the anti-inflammatory effects of LIPA or MVPA breaks during prolonged sitting remains unclear.

METHODS

A systematic search was done on six peer-reviewed databases through January 27th, 2023. Two authors independently screened the citations for eligibility, and risk of bias and performed a meta-analysis.

RESULTS

The included studies originated from high and upper - middle income countries. Observational studies of SB interruptions with LIPA showed favourable effects on inflammatory mediators such as higher levels of adiponectin (odds ratio, OR = +0.14; p = 0.02). However, these findings are not supported by the experimental studies. Experimental studies reported non-significant increase in cytokines including IL-1β (standardised mean difference, SMD = 0.11 pg/ml; p = 0.29) and IL-6 (SMD = 0.19 pg/ml; p = 0.46) after interrupting sitting with LIPA breaks. But these LIPA breaks were found to reduce C-reactive protein (SMD = - 0.50 mg/dl; p = 0.85) and IL-8 levels (SMD = -0.08 pg/ml; p = 0.34) but did not reach statistical significance.

CONCLUSION

Interrupting prolonged sitting time with LIPA breaks shows promise for preventing the inflammatory effects associated with prolonged bouts of daily sitting, though the evidence remains in infancy and limited to high- and upper-middle income countries.

Interrupting Prolonged Sitting with Intermittent Walking Increases Postprandial Gut Hormone Responses

INTRODUCTION

Continuous exercise can increase postprandial gut hormone such as glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) responses, but it is unknown whether interrupting prolonged sitting with intermittent walking elicits this effect.

METHOD

Ten participants with central overweight/obesity (7 men and 3 postmenopausal women, 51 ± 5 yr; mean ± SD) completed a randomized crossover study in which they consumed breakfast and lunch in the laboratory while either sitting continuously for the entire 5.5-h period (SIT) or the prolonged sitting interrupted every 20 min by walking briskly (6.4 km·h-1) for 2 min (BREAKS). Blood samples were collected at regular intervals to examine postprandial plasma GLP-1, PYY, and glucose-dependent insulinotropic polypeptide concentrations. Adipose tissue samples were collected at baseline and at the end of the trials to examine changes in net dipeptidyl peptidase 4 secretion from primary explants.

RESULTS

Mean (95% confidence interval) postprandial GLP-1 and PYY incremental area under curve values were elevated by 26% and 31% in the BREAKS trial versus SIT (8.4 [0.7, 16.1] vs 6.7 [-0.8, 14.2], P = 0.001, and 26.9 [8.1, 45.6] vs 20.4 [5.1, 35.8] nmol·330 min·L-1, P = 0.024, respectively) but without any such effect on glucose-dependent insulinotropic polypeptide (P = 0.076) or net adipose tissue dipeptidyl peptidase 4 secretion (P > 0.05).

CONCLUSIONS

Interrupting prolonged sitting with regular short bouts of brisk walking increases postprandial GLP-1 and PYY concentrations in healthy middle-age men and women with central adiposity.

Acute effect of breaking up prolonged sitting on cognition: a systematic review

OBJECTIVES

To review the current evidence on the acute effects of interrupting prolonged periods of sitting with intermittent physical activity (PA) on cognition in healthy populations.

DESIGN

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines.

METHODS

Studies were included if they investigated the acute effects of taking regular PA breaks from sitting on cognition in healthy populations without any cardiovascular disease, history of brain injury, or psychiatric or neurological disorder. Four electronic databases-PubMed, Scopus, MEDLINE and ProQuest-were searched for eligible studies on 20 September 2020. Study quality was assessed using the Physiotherapy Evidence Database scale.

RESULTS

Seven studies, involving 168 participants aged between 18 and 80 years, were eligible for inclusion in this review. Three of the seven studies found positive effects of interrupting sitting with either (a) 3 min of relatively high-intensity (6 km/hour) walking every 30 min on attention and inhibitory control in young adults; (b) hourly breaks with progressively longer duration (10-30 min) of very light-intensity cycling/walking on attention, working memory and cognitive flexibility in adults with obesity; or (c) an initial bout of continuous moderate-intensity exercise, followed by interruption of post-exercise sitting with 3 min breaks of light-intensity walking (3.2 km/hour) every 30 min, on working memory in older adults with overweight.

CONCLUSION

Given the limited evidence with mixed findings on this topic in the literature and the heterogeneity of PA protocols across the included studies, the results regarding the effectiveness of interrupting prolonged sitting with PA breaks in improving cognition warrant further verification.

PROSPERO REGISTRATION NUMBER

CRD42020147536.

Acute cardiometabolic effects of brief active breaks in sitting for patients with rheumatoid arthritis

Exercise is a treatment in rheumatoid arthritis, but participation in moderate-to-vigorous exercise is challenging for some patients. Light-intensity breaks in sitting could be a promising alternative. We compared the acute effects of active breaks in sitting with those of moderate-to-vigorous exercise on cardiometabolic risk markers in patients with rheumatoid arthritis. In a crossover fashion, 15 women with rheumatoid arthritis underwent three 8-h experimental conditions: prolonged sitting (SIT), 30-min bout of moderate-to-vigorous exercise followed by prolonged sitting (EX), and 3-min bouts of light-intensity walking every 30 min of sitting (BR). Postprandial glucose, insulin, c-peptide, triglycerides, cytokines, lipid classes/subclasses (lipidomics), and blood pressure responses were assessed. Muscle biopsies were collected following each session to assess targeted proteins/genes. Glucose [-28% in area under the curve (AUC), P = 0.036], insulin (-28% in AUC, P = 0.016), and c-peptide (-27% in AUC, P = 0.006) postprandial responses were attenuated in BR versus SIT, whereas only c-peptide was lower in EX versus SIT (-20% in AUC, P = 0.002). IL-1β decreased during BR, but increased during EX and SIT (P = 0.027 and P = 0.085, respectively). IL-1ra was increased during EX versus BR (P = 0.002). TNF-α concentrations decreased during BR versus EX (P = 0.022). EX, but not BR, reduced systolic blood pressure (P = 0.013). Lipidomic analysis showed that 7 of 36 lipid classes/subclasses were significantly different between conditions, with greater changes being observed in EX. No differences were observed for protein/gene expression. Brief active breaks in sitting can offset markers of cardiometabolic disturbance, which may be particularly useful for patients who may find it difficult to adhere to exercise.NEW & NOTEWORTHY Exercise is a treatment in rheumatoid arthritis but is challenging for some patients. Light-intensity breaks in sitting could be a promising alternative. Our findings show beneficial, but differential, cardiometabolic effects of active breaks in sitting and exercise in patients with rheumatoid arthritis. Breaks in sitting mainly improved glycemic and inflammatory markers, whereas exercise improved lipidomic and hypotensive responses. Breaks in sitting show promise in offsetting aspects of cardiometabolic disturbance associated with prolonged sitting in rheumatoid arthritis.

Sit less and move more for cardiovascular health: emerging insights and opportunities

Sedentary behaviour - put simply, too much sitting, as a distinct concept from too little exercise - is a novel determinant of cardiovascular risk. This definition provides a perspective that is complementary to the well-understood detrimental effects of physical inactivity. Sitting occupies the majority of the daily waking hours in most adults and has become even more pervasive owing to the COVID-19 pandemic. The potential for a broad cardiovascular health benefit exists through an integrated approach that involves 'sitting less and moving more'. In this Review, we first consider observational and experimental evidence on the adverse effects of prolonged, uninterrupted sitting and the evidence identifying the possible mechanisms underlying the associated risk. We summarize the results of randomized controlled trials demonstrating the feasibility of changing sedentary behaviour. We also highlight evidence on the deleterious synergies between sedentary behaviour and physical inactivity as the underpinnings of our case for addressing them jointly in mitigating cardiovascular risk. This integrated approach should not only reduce the specific risks of too much sitting but also have a positive effect on the total amount of physical activity, with the potential to more broadly benefit the health of individuals living with or at risk of developing cardiovascular disease.

Does breaking up prolonged sitting improve cognitive functions in sedentary adults? A mapping review and hypothesis formulation on the potential physiological mechanisms

Background

Prolonged (excessive) sitting is detrimentally associated with cardiovascular, metabolic and mental health. Moreover, prolonged sitting has been associated with poor executive function, memory, attention and visuospatial skills, which are important cognitive aspects of work performance. Breaking up prolonged sitting with standing or light-intensity exercises at the workplace is recognized as a potential measure in improving cognition. However, preliminary evidence, primarily from acute laboratory experiments, has enabled formulating hypothesis on the possible mechanistic pathways. Hence, the aim of this mapping review is to gather preliminary evidence and substantiate possible physiological mechanisms underpinning the putative effects of breaking prolonged sitting on improving cognitive function among sedentary office workers.

Mapping method

We searched four databases to identify relevant studies that explored the effects of uninterrupted sitting on cognitive function. First, we introduce how prolonged sitting increases the risks of hyperglycemia, autonomic stability, inflammation, adverse hormonal changes and restrictions in cerebral blood flow (CBF) and alters cognitive function. Second, we elucidate the direct and indirect effects of breaking up prolonged sitting time that may prevent a decline in cognitive performance by influencing glycaemic variability, autonomic stability, hormones (brain derived neurotrophic factor, dopamine, serotonin), vascular functions, and CBF. We highlight the importance of breaking up prolonged sitting on metabolic, vascular and endocrine functions, which in turn may improve cognitive functions and eventually foster work productivity. Improved synaptic transmission or neuroplasticity due to increased brain glucose and mitochondrial metabolism, increased endothelial shear and CBF, increased brain neurotrophic factors (dopamine) and accelerated anti-inflammatory functions are some of the hypothetical mechanisms underpinning improved cognitive functions.

Conclusion

We postulate that improving cognitive function by breaking up prolonged sitting periods is biologically plausible with the myriad of (suggested) physiological mechanisms. Future experimental studies to ascertain the aforementioned hypothetical mechanisms and clinical trials to break sedentary behavior and improve cognitive functions in sedentary office workers are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04136-5.

Effects of Interrupting Prolonged Sitting with Physical Activity Breaks on Blood Glucose, Insulin and Triacylglycerol Measures: A Systematic Review and Meta-analysis

BACKGROUND

Physical activity (PA) breaks in sitting time might attenuate metabolic markers relevant to the prevention of type 2 diabetes.

OBJECTIVES

The primary aim of this paper was to systematically review and meta-analyse trials that compared the effects of breaking up prolonged sitting with bouts of PA throughout the day (INT) versus continuous sitting (SIT) on glucose, insulin and triacylglycerol (TAG) measures. A second aim was to compare the effects of INT versus continuous exercise (EX) on glucose, insulin and TAG measures.

METHODS

The review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) recommendations. Eligibility criteria consisted of trials comparing INT vs. SIT or INT vs. one bout of EX before or after sitting, in participants aged 18 or above, who were classified as either metabolically healthy or impaired, but not with other major health conditions such as chronic obstructive pulmonary disease or peripheral arterial disease.

RESULTS

A total of 42 studies were included in the overall review, whereas a total of 37 studies were included in the meta-analysis. There was a standardised mean difference (SMD) of - 0.54 (95% CI - 0.70, - 0.37, p = 0.00001) in favour of INT compared to SIT for glucose. With respect to insulin, there was an SMD of - 0.56 (95% CI - 0.74, - 0.38, p = 0.00001) in favour of INT. For TAG, there was an SMD of - 0.26 (95% CI - 0.44, - 0.09, p = 0.002) in favour of INT. Body mass index (BMI) was associated with glucose responses (β = - 0.05, 95% CI - 0.09, - 0.01, p = 0.01), and insulin (β = - 0.05, 95% CI - 0.10, - 0.006, p = 0.03), but not TAG (β = 0.02, 95% CI - 0.02, 0.06, p = 0.37). When energy expenditure was matched, there was an SMD of - 0.26 (95% CI - 0.50, - 0.02, p = 0.03) in favour of INT for glucose, but no statistically significant SMDs for insulin, i.e. 0.35 (95% CI - 0.37, 1.07, p = 0.35), or TAG i.e. 0.08 (95% CI - 0.22, 0.37, p = 0.62). It is worth noting that there was possible publication bias for TAG outcomes when PA breaks were compared with sitting.

CONCLUSION

The use of PA breaks during sitting moderately attenuated post-prandial glucose, insulin, and TAG, with greater glycaemic attenuation in people with higher BMI. There was a statistically significant small advantage for PA breaks over continuous exercise for attenuating glucose measures when exercise protocols were energy matched, but no statistically significant differences for insulin and TAG. PROSPERO Registration: CRD42017080982.

PROSPERO REGISTRATION

CRD42017080982.

The Energy Cost of Sitting versus Standing Naturally in Man

PURPOSE

Prolonged sitting is a major health concern, targeted via government policy and the proliferation of height-adjustable workstations and wearable technologies to encourage standing. Such interventions have the potential to influence energy balance and thus facilitate effective management of body/fat mass. It is therefore remarkable that the energy cost of sitting versus standing naturally remains unknown.

METHODS

Metabolic requirements were quantified via indirect calorimetry from expired gases in 46 healthy men and women (age, 27 ± 12 yr; mass, 79.3 ± 14.7 kg; body mass index, 24.7 ± 3.1 kg·m, waist/hip, 0.81 ± 0.06) under basal conditions (i.e., resting metabolic rate) and then, in a randomized and counterbalanced sequence, during lying, sitting and standing. Critically, no restrictions were placed on natural/spontaneous bodily movements (i.e., fidgeting) to reveal the fundamental contrast between sitting and standing in situ while maintaining a comfortable posture.

RESULTS

The mean (95% confidence interval [CI]) increment in energy expenditure was 0.18 (95% CI, 0.06-0.31 kJ·min) from resting metabolic rate to lying was 0.15 (95% CI, 0.03-0.27 kJ·min) from lying to sitting and 0.65 (95% CI, 0.53-0.77 kJ·min) from sitting to standing. An ancillary observation was that the energy cost of each posture above basal metabolic requirements exhibited marked interindividual variance, which was inversely correlated with resting heart rate for all postures (r = -0.5; -0.7 to -0.1) and positively correlated with self-reported physical activity levels for lying (r = 0.4; 0.1 to 0.7) and standing (r = 0.6; 0.3-0.8).

CONCLUSIONS

Interventions designed to reduce sitting typically encourage 30 to 120 min·d more standing in situ (rather than perambulation), so the 12% difference from sitting to standing reported here does not represent an effective strategy for the treatment of obesity (i.e., weight loss) but could potentially attenuate any continued escalation of the ongoing obesity epidemic at a population level.