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Trial Outcomes & Findings for Metabolic Adaptations in Response to High Intensity Interval Training in Obese Adults (NCT NCT02706093)

NCT ID: NCT02706093

Last Updated: 2026-08-24

Results Overview

A hyperinsulinemic-euglycemic clamp was used to assess peripheral insulin sensitivity. Briefly, a primed, continuous infusion of insulin (40 mU/m\^2/min) was administered; blood glucose was assessed every 5 minutes and 20% dextrose (D20 enriched with \[6-6 d2\]glucose) was infused at a variable rate to accommodate changes in blood glucose in order to maintain blood glucose at the participants' overnight fasted levels. About 2 hours after beginning the insulin infusion, when blood glucose concentration stabilized without further changes in the rate of D20 infusion for ≥ \~20 minutes, arterialized blood samples were collected every 5 minutes during the final 20 minutes of the clamp for the determination of steady state tracer-labeled glucose enrichment in plasma to calculate the rate of glucose disposal.

Recruitment status

COMPLETED

Study phase

NA

Target enrollment

120 participants

Primary outcome timeframe

Change from Baseline after 3 months of exercise training

Results posted on

2026-08-24

Participant Flow

Subjects were recruited via advertisements posted around the University of Michigan campus, around other local university campuses, by word of mouth, newspaper advertisements, web-based posting boards, and data sets from the University of Michigan Data Office for Clinical \& Translational Research. Individuals who voluntarily completed our online general screening questionnaire in the past, and gave permission to keep the information from their responses, were also contacted for recruitment.

73 subjects withdrew after eligibility was confirmed, but before starting the study protocol intervention for various reasons: 5 subjects became ineligible, 39 subjects declined participation, 2 subjects were withdrawn by study team due to issues with IVs, 3 subjects relocated and were no longer able to participate, 11 subjects were withdrawn by study team due to pharmacy issues, 13 subjects were lost to follow-up.

Participant milestones

Participant milestones
Measure
High-Intensity Interval Training (HIIT)
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
Overall Study
STARTED
25
22
Overall Study
COMPLETED
14
12
Overall Study
NOT COMPLETED
11
10

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

Metabolic Adaptations in Response to High Intensity Interval Training in Obese Adults

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure
High-Intensity Interval Training (HIIT)
n=25 Participants
The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT#1 training protocol of total of 10 x 1min intervals at 90%HRmax (Figure 8), and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-intensity Continuous Training (MICT)
n=22 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training
Total
n=47 Participants
Total of all reporting groups
Race (NIH/OMB)
Native Hawaiian or Other Pacific Islander
0 Participants
n=1541 Participants
1 Participants
n=1121 Participants
1 Participants
n=2662 Participants
Age, Categorical
<=18 years
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants
Age, Categorical
Between 18 and 65 years
25 Participants
n=1541 Participants
22 Participants
n=1121 Participants
47 Participants
n=2662 Participants
Age, Categorical
>=65 years
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants
Sex: Female, Male
Female
18 Participants
n=1541 Participants
16 Participants
n=1121 Participants
34 Participants
n=2662 Participants
Sex: Female, Male
Male
7 Participants
n=1541 Participants
6 Participants
n=1121 Participants
13 Participants
n=2662 Participants
Ethnicity (NIH/OMB)
Hispanic or Latino
1 Participants
n=1541 Participants
0 Participants
n=1121 Participants
1 Participants
n=2662 Participants
Ethnicity (NIH/OMB)
Not Hispanic or Latino
24 Participants
n=1541 Participants
22 Participants
n=1121 Participants
46 Participants
n=2662 Participants
Ethnicity (NIH/OMB)
Unknown or Not Reported
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants
Race (NIH/OMB)
American Indian or Alaska Native
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants
Race (NIH/OMB)
Asian
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants
Race (NIH/OMB)
Black or African American
6 Participants
n=1541 Participants
5 Participants
n=1121 Participants
11 Participants
n=2662 Participants
Race (NIH/OMB)
White
19 Participants
n=1541 Participants
15 Participants
n=1121 Participants
34 Participants
n=2662 Participants
Race (NIH/OMB)
More than one race
0 Participants
n=1541 Participants
1 Participants
n=1121 Participants
1 Participants
n=2662 Participants
Race (NIH/OMB)
Unknown or Not Reported
0 Participants
n=1541 Participants
0 Participants
n=1121 Participants
0 Participants
n=2662 Participants

PRIMARY outcome

Timeframe: Change from Baseline after 3 months of exercise training

A hyperinsulinemic-euglycemic clamp was used to assess peripheral insulin sensitivity. Briefly, a primed, continuous infusion of insulin (40 mU/m\^2/min) was administered; blood glucose was assessed every 5 minutes and 20% dextrose (D20 enriched with \[6-6 d2\]glucose) was infused at a variable rate to accommodate changes in blood glucose in order to maintain blood glucose at the participants' overnight fasted levels. About 2 hours after beginning the insulin infusion, when blood glucose concentration stabilized without further changes in the rate of D20 infusion for ≥ \~20 minutes, arterialized blood samples were collected every 5 minutes during the final 20 minutes of the clamp for the determination of steady state tracer-labeled glucose enrichment in plasma to calculate the rate of glucose disposal.

Outcome measures

Outcome measures
Measure
High-Intensity Interval Training (HIIT)
n=16 Participants
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
n=15 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
Insulin Sensitivity
Before exercise training (Baseline)
9.7 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 4.0
8.3 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 3.9
Insulin Sensitivity
After 3 months of exercise training (48-72 hours after the last exercise training session)
10.5 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 4.7
8.8 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 3.9
Insulin Sensitivity
Change between baseline and after 3 months of training
0.79 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 3.6
0.43 mg glucose/kg FFM/insulin (uUml)/min
Standard Deviation 2.3

SECONDARY outcome

Timeframe: Change from Baseline after 3 months of exercise training

Change in aerobic capacity between baseline and after 3 months of training

Outcome measures

Outcome measures
Measure
High-Intensity Interval Training (HIIT)
n=16 Participants
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
n=15 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
VO2peak
Before exercise training (Baseline)
2.5 Liters/min
Standard Deviation 0.6
2.4 Liters/min
Standard Deviation 0.5
VO2peak
After 3 months of exercise training (48-72 hours after the last exercise training session)
2.80 Liters/min
Standard Deviation 0.6
2.6 Liters/min
Standard Deviation 0.5
VO2peak
change between Baseline and after 3 months of training
0.30 Liters/min
Standard Deviation 0.17
0.15 Liters/min
Standard Deviation 0.29

SECONDARY outcome

Timeframe: Change from Baseline after 3 months of exercise training

energy expenditure while at rest

Outcome measures

Outcome measures
Measure
High-Intensity Interval Training (HIIT)
n=16 Participants
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
n=15 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
Resting Metabolic Rate
After exercise training
1462 kcal/day
Standard Deviation 201
1462 kcal/day
Standard Deviation 202
Resting Metabolic Rate
Before exercise training (Baseline)
1469 kcal/day
Standard Deviation 172
1477 kcal/day
Standard Deviation 230
Resting Metabolic Rate
change from baseline after 3 months of exercise training
-7 kcal/day
Standard Deviation 124
-15 kcal/day
Standard Deviation 151

SECONDARY outcome

Timeframe: Change from Baseline after 3 months of exercise training

Population: MRI images for 4 subjects (1 HIIT subject and 3 MICT subjects) were not legible for Hepatic fat analyses

Change in abundance of fat in the liver - reported as % area (measured by MRI)

Outcome measures

Outcome measures
Measure
High-Intensity Interval Training (HIIT)
n=15 Participants
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
n=12 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
Hepatic Fat %
Before exercise training (Baseline)
8.7 % area
Standard Deviation 7.5
10.4 % area
Standard Deviation 10.0
Hepatic Fat %
After 3 months of exercise training (48-72 hours after the last exercise training session)
7.5 % area
Standard Deviation 5.4
9.0 % area
Standard Deviation 7.3
Hepatic Fat %
Change between Baseline and after 3 months of training
-1.0 % area
Standard Deviation 3.7
-1.3 % area
Standard Deviation 5.3

SECONDARY outcome

Timeframe: Change from Baseline after 3 months of exercise training

Population: MRI images for 4 subjects (1 HIIT subject and 3 MICT subjects) were not legible for Visceral fat analyses

Change in fat accumulation in the visceral region - measured by MRI

Outcome measures

Outcome measures
Measure
High-Intensity Interval Training (HIIT)
n=15 Participants
High intensity interval training #1 (HIIT): The first session of the "ramp-up" period for HIIT will entail 19min of conventional exercise at 65%HRmax, followed immediately by 2 x 1min intervals at 90%HRmax with a 1 min active recovery period between intervals at 50%HRmax, and a 3min cool down at 60%HRmax after the second interval. After that first ramp up training session, 1 additional high intensity interval will be added to each training session, so by the beginning of the 3rd week of HIIT training, subjects will reach the full HIIT training protocol of total of 10 x 1min intervals at 90%HRmax, and they will continue this training protocol (4d/wk) throughout the 3 month intervention. Subjects who may feel challenged by the rate of increase in the number of intervals during this ramp up period will be allowed to increase the number of intervals at a slower pace, but all subjects must reach the full HIIT protocol during the 4th week of HIIT training. We do not believe that completing a few less intervals each session during the first few weeks of the 3 month training program will influence the outcomes.
Moderate-Intensity Continuous Training (MICT)
n=12 Participants
Moderate-intensity continuous training (MICT): Subjects randomized to MICT will undergo a ramp-up period to build up to a total exercise time of 45min. During the first week of ramp-up, subjects will warm up for 3 min at 60%HRmax, followed by 25min at 70%HRmax and a 3 min cool-down. Subjects will increase exercise time at 70%HRmax by 5min each week, until they reach a total exercise time of 45min (Figure 9), which should be achieved by the 4th week of training. Subjects who feel challenged by the rate of increase during this ramp up period will be allowed to ramp up at a slower pace, but all subjects must reach a total exercise time of 45min by the 5th week of training.
Visceral Fat Area (cm^2)
After 3 months of exercise training (48-72 hours after the last exercise training session)
161 cm^2
Standard Deviation 77
155 cm^2
Standard Deviation 70
Visceral Fat Area (cm^2)
Change between Baseline and after 3 months of training
-6.6 cm^2
Standard Deviation 22.5
-2.2 cm^2
Standard Deviation 22.1
Visceral Fat Area (cm^2)
Before exercise training (Baseline)
169 cm^2
Standard Deviation 70
157 cm^2
Standard Deviation 74

Adverse Events

High Intensity Interval Training (HIIT)

Serious events: 0 serious events
Other events: 0 other events
Deaths: 0 deaths

Moderate Intensity Continuous Training (MICT)

Serious events: 0 serious events
Other events: 0 other events
Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Jeffrey F. Horowitz

University of Michigan

Phone: (734) 647-1076

Results disclosure agreements

  • Principal investigator is a sponsor employee
  • Publication restrictions are in place