Effect of low-volume exercise on hepatic steatosis in adults with obesity plus normal glucose, prediabetes or type 2 diabetes: a randomised controlled trial
Question
Does 12 weeks of combined low-volume high-intensity aerobic exercise and progressive resistance training reduce hepatic steatosis and improve cardiometabolic outcomes in inactive adults with overweight/obesity across glucose-status strata?
Summary
This randomized trial tested whether a modest 12-week exercise program combining low-volume HIIT and progressive resistance training could reduce liver fat in inactive adults with overweight or obesity and normal glucose, prediabetes, or newly diagnosed type 2 diabetes. The program did not significantly reduce liver fat in the whole sample compared with a stretching control, although people with prediabetes showed a subgroup reduction and a weight-stable sensitivity analysis favored exercise. The program improved several cardiometabolic and fitness-related measures, including fasting glucose, triglycerides, estimated cardiovascular risk, liver enzymes, strength, and in the weight-stable analysis VO2peak. Supervised attendance was about 80%, and no intervention-related adverse events were reported.
Methodology
- Inactive adults with overweight/obesity and normal glucose, prediabetes, or newly diagnosed type 2 diabetes.
- 162 participants.
- Stationary cycling plus machine resistance training; home HIIT used available modality.
- Work intervals: One 4-min HIIT bout.
- Intensity: HIIT 85-95% age-predicted HRmax after ramp-in; resistance 80% 1RM.
- Not fully reported; supervised session included 4 min HIIT plus resistance training.
- 3 HIIT sessions/week; 2 supervised combined sessions/week plus 1 home HIIT session/week.
- 12 weeks.
- Parallel-group randomized controlled trial with exercise versus sham stretching control, stratified by glucose group.
- Hepatic steatosis, VO2peak, Strength, and Fasting glucose and HOMA-IR were tracked.
Outcomes
Hepatic steatosis
Primary whole-sample hepatic steatosis change was not significantly different between exercise and control.
Exercise -1.3% (SD 4.9) vs control +0.1% (SD 7.1), p=0.22.
Prediabetes subgroup hepatic steatosis
Participants with prediabetes had a significant liver-fat reduction with exercise compared with control.
Exercise -1.2% vs control +1.7%, p=0.019.
Weight-stable sensitivity analysis
Among participants with less than 5% body-weight change, exercise reduced hepatic steatosis and improved several metabolic and fitness markers.
Hepatic steatosis p=0.017; VO2peak p=0.047; HOMA-IR p=0.041; ASCVD risk p=0.008.
Strength
Exercise increased leg press, seated row, and chest press strength compared with control.
All three strength outcomes p<0.001.
Safety
The intervention was completed with no intervention-related adverse events.
80% supervised session attendance; no related adverse events.
Insights
- A very low HIIT dose can be feasible and well attended in screened, previously inactive adults when ramped up and partly supervised.
- One 4-min hard interval paired with resistance training should not be marketed as a reliable liver-fat reduction protocol because the primary whole-sample endpoint was null.
- Prediabetes may be a more responsive subgroup for liver-fat change than normal glucose or newly diagnosed type 2 diabetes in this protocol.
- For app translation, fidelity tracking is important because the study did not measure the unsupervised weekly HIIT session.
Limitations
- COVID-19 disruptions paused and modified the intervention.
- Unsupervised home HIIT adherence and intensity were not measured.
- Lifestyle changes outside the intervention could influence liver fat and metabolic outcomes.
- Participants were not blinded.
- The protocol used resistance machines and clinical supervision.
Safety
- No adverse events related to the intervention.
- Authors recommend supervision for people with high cardiovascular risk.
- COVID-19 lockdowns required pauses or telehealth maintenance for some exercise participants.