Effect of Breaking up Prolonged Sitting on Metabolic Flexibility

University of Colorado, Denver28 enrolled

Overview

The investigators propose in this project to determine the effect of 3 days of frequent interruption of prolonged sitting on metabolic health in healthy overweight sedentary adults (n=24), as compared to 3 days including a single long bout of isocaloric exercise or a control condition where subjects do not exercise but are subjected to prolonged sitting. The investigators believe that this proposed project will provide an initial evidence base for the health benefits of breaking up prolonged sitting with short bursts of moderate-intensity activity, like walking.

Although public-health recommendations to engage in moderate-to-vigorous physical activity (at least 30min, 5 days / week) have been widely promulgated by the government, most people are physically inactive. Sedentary behaviors, like time spent sitting, are associated with serious implications on metabolic health, indicating that even in individuals who regularly exercise a reduction in time spent sitting can confer health benefits. Encouraging recent evidence shows that walking breaks throughout the day are an effective strategy to offset the deleterious effects of prolonged uninterrupted sitting. Further data however are needed to better understand the effect of these microbursts of activity along the day. The investigators propose in this project to determine the effect of 3 days of frequent interruption of prolonged sitting on metabolic health in healthy overweight sedentary adults (n=24), as compared to 3 days including a single long bout of isocaloric exercise or a control condition where subjects do not exercise but are subjected to prolonged sitting. Plasma glucose, insulin, triglycerides and free fatty acids concentrations and the use of substrate (glucose, fat or protein) to provide energy to the body in response to meals consumption will be measured on day 3 of each of these three conditions. The investigators will furthermore assess the ability of the participants to perform the interventions on physical activity at the end of each day over the three days of intervention (2 days in free-living conditions and one day in a controlled environment). The investigators believe that this proposed project will provide an initial evidence base for the health benefits of breaking up prolonged sitting with short bursts of moderate-intensity activity, like walking. This innovative strategy may be more effective at combating the adverse effects of sedentary behaviors than more traditional approaches like structured exercise.

Study Type

INTERVENTIONAL

Allocation

Conditions

Health Behavior

Interventions

Uninterrupted sittingBEHAVIORAL

Subjects will be asked to refrain for two days from any structured activity and to reduce any daily life activity (walking, taking the stairs, biking, etc.) in their daily life. On day 3, subjects will remain seated all day in the room calorimeter, except to rise from the chair to void.

Sitting + 1 bout of activityBEHAVIORAL

Subjects will be asked to perform 45 minutes of moderate-exercise in the morning once per day for two days in their daily life. On day 3 they will remain seated all day in the room calorimeter, except to rise from the chair to void, and to perform one bout of 45-min moderate-intensity (defined below) walking on a treadmill at 1000.

Sitting + microbursts of activityBEHAVIORAL

Eligibility

Sex: ALLMin age: 19 YearsMax age: 45 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * overweight but weight stable (less than +/- 3kg over previous 6 months) male and female adults (n=24) will be recruited. * age between 19-45 years old, * a BMI of 27-33 kg/m2, * inactive (≤ 1.5hr/wk of moderate-to-vigorous activity), * sedentary (office employees who are spending more than 6hrs/day in sitting position) and * English-speaking. Exclusion Criteria: * any history of renal, cardiovascular or hepatic diseases, * type 1 or 2 diabetes, * cancer, * pregnancy, * smoking, * consumption of drugs or alcohol (\>40g/d), * any medications known to interfere with lipid or energy metabolism, * known physical activity contraindications, or major illness/physical problems (acute or chronic) that may limit their ability to perform the walking activities and * menopause (defined as no menses in the prior 6 months). The use of birth pill control will be accepted. Women are asked to avoid pregnancy until completion of Condition C.

Locations (1)

University of Colorado Hospital

Aurora, Colorado, United States

Outcomes

Primary Outcomes

Total substrate oxidation

Total fat oxidation during the test day will be determined using whole-room indirect calorimetry. O2 consumption and CO2 production will be determined from the flow rates and differences in gas concentrations between air entering and air exiting the calorimeter as previously described

Time frame: 1 day

Postprandial plasma insulin and glucose response

Plasma glucose and insulin will be measured in fasting conditions and hourly during 12hrs following a standard meal consumption. The area under the curve will be calculated for both plasma glucose and insulin. This area will represent the postprandial response to a meal for both insulin and glucose.

Time frame: 1 day

Dietary fat oxidation

Subjects will collect their own hourly breath sampling for 13CO2 by blowing through a straw into two 15ml Vacutainer after the investigators will have shown them the procedure. Breath CO2 will be sampled directly from the Vacutainer with a syringe, and 13CO2 /12CO2 measured with Isotopic Ratio Mass Spectrometer (IRMS).

Time frame: 1 day

Data from ClinicalTrials.gov

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