Trends in spontaneous physical activity and energy expenditure among adults in a respiratory chamber, 1985 to 2005

Abstract

Objective Fidgeting, a type of spontaneous physical activity (SPA), has substantial thermogenic potential. This research aims to examine secular trends in SPA and energy expenditure (EE) inside a respiratory chamber. Methods From 1985 to 2005, healthy adults (n = 678; mean age: 28.8 years; men: 60%; 522 Indigenous American, 129 White, and 27 Black) had a 24‐hour stay in the respiratory chamber equipped with radar sensors. Body composition, glucose tolerance, fasting insulin, insulin action (hyperinsulinemic‐euglycemic clamp), and insulin secretion (intravenous glucose tolerance test) were measured as covariates. Results SPA, adjusted for age, sex, race, and body composition, declined (r = −0.30, p < 0.0001), with a concomitant rise in the energy cost of SPA (r = 0.30, p < 0.0001). The 24‐hour EE adjusted for covariates increased (r = 0.31, p < 0.0001), which was reflected in increases in EE during sleep (r = 0.18, p < 0.0001) and during the awake, fed condition (r = 0.28, p < 0.0001). The secular trends in SPA or 24‐hour EE were unchanged with adjustment for measures related to glucose metabolism. Conclusions Secular trend analyses showed a decline in fidgeting. However, this decline in SPA was partially counterbalanced by an increase in energy cost of this activity and a rise in EE. Nevertheless, our results support public health efforts to promote small but sustained changes in these behaviors.

Secular trends and determinants of ad libitum energy intake measured in a research setting from 1999-2020

“…In previous studies, SPA demonstrated a significant change over time and was therefore added to time and intake models ( 15 ). After including SPA, time remained significant in all intake models: total ( β = −51 kcal/year, p < 0.0001), %WMEN ( β = −2%/year, p < 0.0001), protein ( β = −10 kcal/year, p < 0.0001), fat ( β = −23 kcal/year, p < 0.0001), and carbohydrate ( β = −23 kcal/year, p < 0.0001).…”

“…In several previously reported studies, as well as our results above, intake was significantly positively associated with SPA that is limited to restless and fidgeting-like behaviors possible in the whole-room calorimeter ( 1 , 5 ). Additionally, Travis et al ( 15 ) demonstrated a secular decline in SPA. If the decline in SPA is representative of an overall decrease in physical activity, this could be reflected in less drive to eat (e.g., reduced activity reducing drive for intake).…”

“…Previous studies in our unit have associated both SPA and FFM index with dietary intake ( 5 , 16 ). In this case, SPA reflects small restless physical movements participants make in the respiratory chambers, like sitting to standing, and is a tiny yet highly variable component of energy expenditure ( 15 ). In all season and secular models, FFM index and SPA were significant positive predictors of intake and thus were essential features of each model.…”

“…Additionally, our group has previously identified temporal decreases in spontaneous physical activity (SPA) and a positive association between SPA, as used in the constrained space of the whole-room calorimeter, and energy intake ( 5 , 15 ). Briefly, in our study, SPA is a measure of physical activity that is associated with fidgeting-like behaviors and small preferences for movement, such as standing instead of sitting ( 15 ). Even though it is a small component of overall energy expenditure, it is highly variable and easily measured in certain study paradigms (like a metabolic chamber) ( 15 ).…”

“…Briefly, in our study, SPA is a measure of physical activity that is associated with fidgeting-like behaviors and small preferences for movement, such as standing instead of sitting ( 15 ). Even though it is a small component of overall energy expenditure, it is highly variable and easily measured in certain study paradigms (like a metabolic chamber) ( 15 ). Thus, SPA was included in models to investigate how temporal factors (i.e., seasonality and secular trends over time) affect the relationship between SPA and food intake.…”