Successfully Reducing Sitting Time Can Improve Metabolic Flexibility

Taru Garthwaite; Tanja Sjöros; Saara Laine; Mikko Koivumäki; Henri Vähä-Ypyä; Jooa Norha; Petri Kallio; Maria Saarenhovi; Eliisa Löyttyniemi; Harri Sievänen; Noora Houttu; Kirsi Laitinen; Kari K. Kalliokoski; Tommi Vasankari; Juhani Knuuti; Ilkka Heinonen

doi:10.1111/sms.70113

Successfully Reducing Sitting Time Can Improve Metabolic Flexibility

Taru Garthwaite^*
, Tanja Sjöros
, Saara Laine
, Mikko Koivumäki
, Henri Vähä-Ypyä
, Jooa Norha
, Petri Kallio
, Maria Saarenhovi
, Eliisa Löyttyniemi
, Harri Sievänen
, Noora Houttu
, Kirsi Laitinen
, Kari K. Kalliokoski
, Tommi Vasankari
, Juhani Knuuti
, Ilkka Heinonen

^*Corresponding author for this work

Turku PET Centre

Research output: Contribution to journal › Article › Scientific › peer-review

2 Citations (Scopus)

Abstract

Impaired metabolic flexibility (MetFlex; the ability to regulate substrate oxidation) and sedentary behavior are both linked to cardiometabolic diseases, but the relationship between the two is not fully elucidated. This study investigated the effects of reduced sedentary time on MetFlex. Sixty-four sedentary adults with metabolic syndrome were randomized into intervention (INT, n = 33) and control (CON, n = 31) groups. INT aimed to reduce sedentary time by 1 h/day by increasing standing and non-exercise physical activity (PA) for 6 months, with continuous accelerometry. Substrate oxidation and MetFlex [ΔRER (respiratory exchange ratio)] from fasting to hyperinsulinemic-euglycemic clamp and low- to maximal-intensity exercise were assessed with indirect calorimetry. Intervention effects between INT and CON were analyzed with mixed models, and secondary analyses examined the effects based on accelerometer-derived behavior changes. INT reduced sedentary time by 41 min/day. Neither insulin- nor exercise-stimulated MetFlex changed in INT or CON, but carbohydrate oxidation during maximal exercise changed differently, favoring INT [INT +2.6 (95% CI: −6.1, 0.8), CON −1.4 (−2.1, 4.9) mg/kg/min; group * time p = 0.03]. In secondary analyses, those who successfully reduced sedentary time by at least 30 min/day (n = 34) improved insulin-stimulated MetFlex and low-intensity exercise fat oxidation compared to the continuously sedentary (n = 30) [ΔRER +0.03 (−0.01, 0.07) vs. −0.02 (−0.06, 0.03); and FATox +0.2 (−0.3, 0.7) vs. −0.4 (−1.0, 1.0) mg/kg/min, group * time p < 0.05]. Changes in insulin-stimulated MetFlex correlated with changes in standing and insulin sensitivity. Thus, successfully reducing daily sitting by at least half an hour can improve MetFlex, with parallel insulin sensitivity enhancements, and aid in cardiometabolic disease prevention in risk populations. Trial Registration: https://www.clinicaltrials.gov/study/NCT03101228.

Original language	English
Article number	e70113
Journal	Scandinavian Journal of Medicine and Science in Sports
Volume	35
Issue number	8
DOIs	https://doi.org/10.1111/sms.70113
Publication status	Published - Aug 2025
MoE publication type	A1 Journal article-refereed

Funding

This study was conducted within the Centre of Excellence in Cardiovascular and Metabolic Research, supported by the Research Council of Finland, University of Turku, Åbo Akademi University, and Turku University Hospital. We thank the staff of Turku PET Centre, University of Turku, and the laboratory personnel in the Turku University Hospital Laboratory for their assistance. Open access publishing facilitated by Turun yliopisto, as part of the Wiley ‐ FinELib agreement. Funding: This work was supported by the Research Council of Finland, Finnish Cultural Foundation, Finnish Diabetes Research Foundation, Hospital District of Southwest Finland, and Juho Vainio Foundation. This study was conducted within the Centre of Excellence in Cardiovascular and Metabolic Research, supported by the Research Council of Finland, University of Turku, Åbo Akademi University, and Turku University Hospital. We thank the staff of Turku PET Centre, University of Turku, and the laboratory personnel in the Turku University Hospital Laboratory for their assistance. Open access publishing facilitated by Turun yliopisto, as part of the Wiley - FinELib agreement. This work was supported by the Research Council of Finland, Finnish Cultural Foundation, Finnish Diabetes Research Foundation, Hospital District of Southwest Finland, and Juho Vainio Foundation. Funding:

Keywords

energy metabolism
metabolic flexibility
metabolic syndrome
physical activity
sedentary behavior

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10.1111/sms.70113Licence: CC BY

Scandinavian Med Sci Sports - 2025 - Garthwaite - Successfully Reducing Sitting Time Can Improve Metabolic FlexibilityFinal published version, 676 KBLicence: CC BY

https://urn.fi/URN:NBN:fi-fe2026022716734

Cite this

Garthwaite, T., Sjöros, T., Laine, S., Koivumäki, M., Vähä-Ypyä, H., Norha, J., Kallio, P., Saarenhovi, M., Löyttyniemi, E., Sievänen, H., Houttu, N., Laitinen, K., Kalliokoski, K. K., Vasankari, T., Knuuti, J., & Heinonen, I. (2025). Successfully Reducing Sitting Time Can Improve Metabolic Flexibility. Scandinavian Journal of Medicine and Science in Sports, 35(8), Article e70113. https://doi.org/10.1111/sms.70113

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title = "Successfully Reducing Sitting Time Can Improve Metabolic Flexibility",

abstract = "Impaired metabolic flexibility (MetFlex; the ability to regulate substrate oxidation) and sedentary behavior are both linked to cardiometabolic diseases, but the relationship between the two is not fully elucidated. This study investigated the effects of reduced sedentary time on MetFlex. Sixty-four sedentary adults with metabolic syndrome were randomized into intervention (INT, n = 33) and control (CON, n = 31) groups. INT aimed to reduce sedentary time by 1 h/day by increasing standing and non-exercise physical activity (PA) for 6 months, with continuous accelerometry. Substrate oxidation and MetFlex [ΔRER (respiratory exchange ratio)] from fasting to hyperinsulinemic-euglycemic clamp and low- to maximal-intensity exercise were assessed with indirect calorimetry. Intervention effects between INT and CON were analyzed with mixed models, and secondary analyses examined the effects based on accelerometer-derived behavior changes. INT reduced sedentary time by 41 min/day. Neither insulin- nor exercise-stimulated MetFlex changed in INT or CON, but carbohydrate oxidation during maximal exercise changed differently, favoring INT [INT +2.6 (95\% CI: −6.1, 0.8), CON −1.4 (−2.1, 4.9) mg/kg/min; group * time p = 0.03]. In secondary analyses, those who successfully reduced sedentary time by at least 30 min/day (n = 34) improved insulin-stimulated MetFlex and low-intensity exercise fat oxidation compared to the continuously sedentary (n = 30) [ΔRER +0.03 (−0.01, 0.07) vs. −0.02 (−0.06, 0.03); and FATox +0.2 (−0.3, 0.7) vs. −0.4 (−1.0, 1.0) mg/kg/min, group * time p < 0.05]. Changes in insulin-stimulated MetFlex correlated with changes in standing and insulin sensitivity. Thus, successfully reducing daily sitting by at least half an hour can improve MetFlex, with parallel insulin sensitivity enhancements, and aid in cardiometabolic disease prevention in risk populations. Trial Registration: https://www.clinicaltrials.gov/study/NCT03101228.",

keywords = "energy metabolism, metabolic flexibility, metabolic syndrome, physical activity, sedentary behavior",

author = "Taru Garthwaite and Tanja Sj{\"o}ros and Saara Laine and Mikko Koivum{\"a}ki and Henri V{\"a}h{\"a}-Ypy{\"a} and Jooa Norha and Petri Kallio and Maria Saarenhovi and Eliisa L{\"o}yttyniemi and Harri Siev{\"a}nen and Noora Houttu and Kirsi Laitinen and Kalliokoski, \{Kari K.\} and Tommi Vasankari and Juhani Knuuti and Ilkka Heinonen",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Scandinavian Journal of Medicine \& Science In Sports published by John Wiley \& Sons Ltd.",

year = "2025",

month = aug,

doi = "10.1111/sms.70113",

language = "English",

volume = "35",

journal = "Scandinavian Journal of Medicine and Science in Sports",

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Garthwaite, T, Sjöros, T, Laine, S, Koivumäki, M, Vähä-Ypyä, H, Norha, J, Kallio, P, Saarenhovi, M, Löyttyniemi, E, Sievänen, H, Houttu, N, Laitinen, K, Kalliokoski, KK, Vasankari, T, Knuuti, J & Heinonen, I 2025, 'Successfully Reducing Sitting Time Can Improve Metabolic Flexibility', Scandinavian Journal of Medicine and Science in Sports, vol. 35, no. 8, e70113. https://doi.org/10.1111/sms.70113

TY - JOUR

T1 - Successfully Reducing Sitting Time Can Improve Metabolic Flexibility

AU - Garthwaite, Taru

AU - Sjöros, Tanja

AU - Laine, Saara

AU - Koivumäki, Mikko

AU - Vähä-Ypyä, Henri

AU - Norha, Jooa

AU - Kallio, Petri

AU - Saarenhovi, Maria

AU - Löyttyniemi, Eliisa

AU - Sievänen, Harri

AU - Houttu, Noora

AU - Laitinen, Kirsi

AU - Kalliokoski, Kari K.

AU - Vasankari, Tommi

AU - Knuuti, Juhani

AU - Heinonen, Ilkka

PY - 2025/8

Y1 - 2025/8

N2 - Impaired metabolic flexibility (MetFlex; the ability to regulate substrate oxidation) and sedentary behavior are both linked to cardiometabolic diseases, but the relationship between the two is not fully elucidated. This study investigated the effects of reduced sedentary time on MetFlex. Sixty-four sedentary adults with metabolic syndrome were randomized into intervention (INT, n = 33) and control (CON, n = 31) groups. INT aimed to reduce sedentary time by 1 h/day by increasing standing and non-exercise physical activity (PA) for 6 months, with continuous accelerometry. Substrate oxidation and MetFlex [ΔRER (respiratory exchange ratio)] from fasting to hyperinsulinemic-euglycemic clamp and low- to maximal-intensity exercise were assessed with indirect calorimetry. Intervention effects between INT and CON were analyzed with mixed models, and secondary analyses examined the effects based on accelerometer-derived behavior changes. INT reduced sedentary time by 41 min/day. Neither insulin- nor exercise-stimulated MetFlex changed in INT or CON, but carbohydrate oxidation during maximal exercise changed differently, favoring INT [INT +2.6 (95% CI: −6.1, 0.8), CON −1.4 (−2.1, 4.9) mg/kg/min; group * time p = 0.03]. In secondary analyses, those who successfully reduced sedentary time by at least 30 min/day (n = 34) improved insulin-stimulated MetFlex and low-intensity exercise fat oxidation compared to the continuously sedentary (n = 30) [ΔRER +0.03 (−0.01, 0.07) vs. −0.02 (−0.06, 0.03); and FATox +0.2 (−0.3, 0.7) vs. −0.4 (−1.0, 1.0) mg/kg/min, group * time p < 0.05]. Changes in insulin-stimulated MetFlex correlated with changes in standing and insulin sensitivity. Thus, successfully reducing daily sitting by at least half an hour can improve MetFlex, with parallel insulin sensitivity enhancements, and aid in cardiometabolic disease prevention in risk populations. Trial Registration: https://www.clinicaltrials.gov/study/NCT03101228.

AB - Impaired metabolic flexibility (MetFlex; the ability to regulate substrate oxidation) and sedentary behavior are both linked to cardiometabolic diseases, but the relationship between the two is not fully elucidated. This study investigated the effects of reduced sedentary time on MetFlex. Sixty-four sedentary adults with metabolic syndrome were randomized into intervention (INT, n = 33) and control (CON, n = 31) groups. INT aimed to reduce sedentary time by 1 h/day by increasing standing and non-exercise physical activity (PA) for 6 months, with continuous accelerometry. Substrate oxidation and MetFlex [ΔRER (respiratory exchange ratio)] from fasting to hyperinsulinemic-euglycemic clamp and low- to maximal-intensity exercise were assessed with indirect calorimetry. Intervention effects between INT and CON were analyzed with mixed models, and secondary analyses examined the effects based on accelerometer-derived behavior changes. INT reduced sedentary time by 41 min/day. Neither insulin- nor exercise-stimulated MetFlex changed in INT or CON, but carbohydrate oxidation during maximal exercise changed differently, favoring INT [INT +2.6 (95% CI: −6.1, 0.8), CON −1.4 (−2.1, 4.9) mg/kg/min; group * time p = 0.03]. In secondary analyses, those who successfully reduced sedentary time by at least 30 min/day (n = 34) improved insulin-stimulated MetFlex and low-intensity exercise fat oxidation compared to the continuously sedentary (n = 30) [ΔRER +0.03 (−0.01, 0.07) vs. −0.02 (−0.06, 0.03); and FATox +0.2 (−0.3, 0.7) vs. −0.4 (−1.0, 1.0) mg/kg/min, group * time p < 0.05]. Changes in insulin-stimulated MetFlex correlated with changes in standing and insulin sensitivity. Thus, successfully reducing daily sitting by at least half an hour can improve MetFlex, with parallel insulin sensitivity enhancements, and aid in cardiometabolic disease prevention in risk populations. Trial Registration: https://www.clinicaltrials.gov/study/NCT03101228.

KW - energy metabolism

KW - metabolic flexibility

KW - metabolic syndrome

KW - physical activity

KW - sedentary behavior

UR - https://www.scopus.com/pages/publications/105012961677

U2 - 10.1111/sms.70113

DO - 10.1111/sms.70113

M3 - Article

C2 - 40781908

AN - SCOPUS:105012961677

SN - 0905-7188

VL - 35

JO - Scandinavian Journal of Medicine and Science in Sports

JF - Scandinavian Journal of Medicine and Science in Sports

IS - 8

M1 - e70113

ER -

Successfully Reducing Sitting Time Can Improve Metabolic Flexibility

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