Continuous Exercise but Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults
Question
Does 12 weeks of HIIT improve body composition and cardiovascular risk factors as well as continuous aerobic exercise or placebo exercise in previously inactive overweight adults?
Summary
In previously inactive overweight adults, 12 weeks of supervised cycling HIIT improved work capacity about as much as longer continuous cycling, but it did not reduce total, trunk, or android fat the way continuous training did. The HIIT protocol was well tolerated with no adverse events during HIIT testing or training.
Methodology
- Previously inactive overweight adults aged 18-55
- 38 participants.
- Cycle ergometer.
- Work intervals: 30-45 s during progression; 60 s from week 5.
- Recovery: 120-180 s at 30 W during progression; 120 s from week 5.
- Intensity: 120% VO2peak; RPE 18-20 achieved.
- 20-24 min including warm-up/cool-down.
- 3 sessions/week.
- 12 weeks.
- Randomized placebo-controlled trial
- Work capacity, Body fat distribution, Blood pressure, and Blood biomarkers were tracked.
Outcomes
Work capacity
HIIT and continuous training improved work capacity similarly; placebo did not.
Group x time p<0.001; HIIT +22.3 +/- 3.5%, CONT +23.8 +/- 3.0%, PLA +3.1 +/- 5.0%; HIIT vs CONT p=0.86.
Body fat
Continuous training reduced total body fat, while HIIT did not.
Total body fat main effect p=0.049; CONT -2.6 +/- 1.1%, HIIT -0.3 +/- 0.6%, PLA -0.7 +/- 0.4%.
Android fat
Android fat fell in continuous and placebo groups but not HIIT.
p=0.04; CONT -2.7 +/- 1.3%, PLA -1.4 +/- 0.8%, HIIT +0.8 +/- 0.6%; HIIT vs CONT p=0.01.
Blood markers
Most serum markers did not show group-by-time changes; total cholesterol and LDL-C did.
No group x time for AST, ALT, hs-CRP, triglycerides, HDL-C, insulin, glucose; significant group x time for total cholesterol and LDL-C.
Safety
HIIT had no reported adverse events and high compliance among completers.
Compliance 96%; no adverse events during HIIT testing or training.
Insights
- HIIT can be programmed as a time-efficient fitness intervention for inactive overweight adults.
- Do not use this trial to claim HIIT improves fat distribution as well as longer continuous exercise.
- For less-trained adults, a non-all-out cycling format with long recovery and supervision was used.
Limitations
- Small sample with 33 completers
- Mostly female and Caucasian sample
- Free-living diet and nonexercise activity not experimentally controlled
- Only one HIIT protocol tested
Safety
- No adverse events during testing or training in HIIT or placebo.
- One syncopal episode occurred during testing in the continuous group.
- HIIT peak systolic BP and HR were kept within submaximal levels considered suitable for exercise training.