# The effects of breaking up sedentary behaviors on energy and substrate metabolism

> **NIH NIH F31** · UNIVERSITY OF COLORADO DENVER · 2021 · $16,718

## Abstract

PROJECT SUMMARY/ABSTRACT
Despite the well-known health benefits of exercise, most adults do not meet physical activity (PA)
recommendations, and the prevalence of metabolic diseases continues to rise. Traditionally, PA is typically
prescribed as a single-continuous bout of 30-60 min per day. The newly released PA guidelines no longer require
PA to be in 10-min bouts and suggest reducing sedentary behaviors (SB). This is important because
epidemiologic and experimental evidence suggest that breaking up SB (i.e. sitting) with short-frequent bouts of
PA acutely decreased glycemia, even in individuals who exercise regularly. However, whether the acute
metabolic effects of interrupting prolonged sitting are sustained over time and outside the laboratory and
potential underlying biological mechanisms remain poorly understood. My dissertation aims to address these
questions in sedentary, physically inactive adults with overweight to obesity. The preliminary data from my
dissertation suggest that breaking up SB with short-frequent PA bouts spread throughout the day acutely
increases the reliance on carbohydrate as fuel over 24h and following a meal, which may explain the decrease
in daily glycemia observed in numerous studies. The objective of this F31 award is to investigate the sustained
(4-week) effect of breaking up SB with short-frequent bouts of PA in overweight to obese, sedentary, physically
inactive adults on glycemic control and potential underlying mechanisms (i.e. 24h and postprandial dietary and
total carbohydrate oxidation), and to compare the effects induced by an intervention matched for total active time
but consisting of a daily-single continuous bout of PA. The benefits of the PA spread throughout the day on
glycemia compared to the daily performance of a single-continuous bout of PA is likely not due to differences in
whole-body insulin sensitivity but to a greater use of carbohydrate as fuel. During the short bouts of activity,
carbohydrate from glycogen stores is likely the primary energy source and then replenished by increasing
skeletal muscle uptake of plasma glucose. Over time, this effect is lasting several hours after the last bout of
activity which decreases postprandial glycemia and daily glucose excursions, along with greater oxidative rates
of total and dietary carbohydrate even when individuals are resting. The proposed studies will provide an initial
evidence base for the health benefits of breaking up prolonged sitting with short bouts of activity, and key
information for future mechanistic studies. This F31 award further outlines a career development plan to
supplement my doctoral training focused on the metabolic effects of PA to facilitate clinical research training in
the use of stable isotope tracer methodology to track substrate metabolism, doubly labelled water method to
derive total daily energy expenditure, use of accelerometry-based monitors to assess the daily patterns of SB
and PA and continuous glucose moni...

## Key facts

- **NIH application ID:** 10265460
- **Project number:** 5F31DK125061-02
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Nathan P DeJong
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $16,718
- **Award type:** 5
- **Project period:** 2020-09-09 → 2022-03-08

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10265460

## Citation

> US National Institutes of Health, RePORTER application 10265460, The effects of breaking up sedentary behaviors on energy and substrate metabolism (5F31DK125061-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10265460. Licensed CC0.

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