3 months of HIIT vs moderate-intensity continuous training (MICT) in obese adults: VO2peak +16% vs +6%; maximal fat oxidation rose only after HIIT; mitochondrial respiration rose in both (+36% vs +67%, no significant difference); after 4 months of follow-up only the HIIT group kept higher VO2peak and fat oxidation
Obese adults trained for 3 months with either MICT or HIIT (about 34 sessions) and were followed for 4 months. Body composition, VO2peak and fat oxidation were measured before, after and at follow-up; vastus lateralis biopsies before and after. Content from the abstract only.
Participants
Thirty-two patients (mean age 39 years; mean BMI 36 kg·m⁻²). Group sizes and sex split are not given in the abstract.
Protocol
3 months of MICT or HIIT, ~34 sessions; 4-month follow-up. Session details (durations, intensities) are not given in the abstract.
Measured: body composition, VO2peak, fat oxidation rate (PRE, POST, follow-up); ex vivo mitochondrial respiration (PRE, POST).
Key Results
Body mass −6% and fat mass −14% at POST in both groups.
VO2peak +6% (MICT) and +16% (HIIT).
Maximal fat oxidation rate increased only after HIIT (P < 0.001).
Maximal ADP-stimulated mitochondrial respiration (normalised to citrate synthase) increased by 67% (MICT) and 36% (HIIT), without significant difference.
After follow-up, body mass and fat mass were still lower (−4% and −20%) in both groups; only after HIIT were VO2peak (+8%) and maximal fat oxidation still higher.
Authors' conclusion: HIIT was more effective in improving and maintaining VO2peak and fat oxidation in obese subjects.
Practical Application
"Is Zone 2 the best way to get better at burning fat?" In a 3-month two-arm trial in 32 obese adults, intervals raised maximal fat oxidation and moderate continuous training did not; both raised mitochondrial respiration with no significant difference, and VO2peak rose more with intervals (+16% vs +6%).
It is training evidence against "Zone 2 is the fat-burning zone that trains fat burning best"; with REF-1092 the base has no training study showing Zone 2 superior for fat oxidation.
Not from this paper; the base's own practice (SYNTH-51): easy work earns its place through volume, low cost and the long ride, not through a unique fat-oxidation effect.
Inference, not tested here: in trained athletes, who already oxidise much more fat, the size of this difference is unknown.
Limitations
Obese, untrained adults; not athletes.
Session durations and intensities, group sizes and whether the two programmes were matched for work or time are not given in the abstract.
Fat oxidation measured during a laboratory test; no performance outcome.
How this entry was checked and changed
Why this level
parallel two-arm trial with 32 (rubric: parallel RCT 20–39 = B+; randomisation not stated in the abstract)