Background

Independent of sedentary time and moderate-to-vigorous activity (MVPA), frequent interruptions of sedentary behaviors (SB) have been associated with improved metabolic profiles (lower C-reactive protein (CRP), glucose, triglycerides - TG and cholesterol levels). Furthermore, breaking up SB acutely reduces postprandial glucose and insulin, and increases carbohydrate oxidation. We aimed to determine whether the benefits persist after the immediate acute exposure and were due to an increase in MVPA, SB and/or total energy expenditure (TEE).

Methods

19 overweight adults (7M/12F, age: 33±8 y, BMI: 29.5±3.3 kg/m2) were randomly assigned to a 4-wk intervention consisting of brisk walking for either 5 min/hr for 9 hrs, 5 d/wk (BREAK, n=10), or 45 min/d, 5d/wk (ONE, n=9). Pre and post intervention fasting inflammatory markers (IL1a, IL6, IL10, TNFα, CRP), TG, cholesterol, HDL and LDL were measured. During a 24h stay in a room calorimeter, substrate use (respiratory quotient - RQ) and plasma glucose and insulin were measured in response to 3 standard meals while subjects rested. Metabolic flexibility (MF, ability to match substrate use to changes in fuel availability) was assessed as the difference between waking and sleeping RQ. MVPA, SB and TEE were measured by accelerometers and DLW.

Results

BREAK and ONE similarly increased MVPA (p=0.09), decreased SB (p=0.03) and unchanged TEE. Both reduced fasting insulin (p=0.07) and none altered inflammatory markers and metabolites. Cholesterol and LDL decreased in BREAK but not in ONE (intervention*time interaction: p=0.06 and p=0.04, respectively). BREAK only decreased postprandial glucose and insulin AUC (-6%, p=0.07 and -22%, p=0.02, respectively). Neither interventions changed 24h and postprandial RQ. MICRO, but not ONE, increased MF index (p=0.02), indicating an improvement.

Conclusions

Breaking up SB for 4 weeks improves metabolic profiles in overweight adults, independently of changes in TEE, MVPA or sedentary time.