Discussion
This is the first randomized control trial which investigated the effects of a 12 week VLCHF diet and HIIT interventions, as well as their combination, on changes of plasma lipidomic and metabolomic profiles in individuals with overweight and obesity. We revealed that the VLCHF diet, alone or combined with HIIT, caused a substantial increase in serum plasmalogens, FAHFAs, FAs, AcCar, CE, SMs, CER, and sulfatides. Glycerophospholipids and TGs substantially decreased in both the VLCHF and VLCHF + HIIT groups. The highest lipid changes occurred already after 4 weeks and then their plasma levels remained stable or showed a countermovement trend until the end of the intervention after 12 weeks (Fig. 