In this study the investigators utilized a novel hybrid HIIT (high intensity interval training) exercise training approach, the Hybrid Interval Training (DoIT) workout that combines interval training, resistance exercise training and functional training in order to test the hypothesis that DoIT will be able to: i) reduce body mass, ii) improve body composition and iii) alter energy balance, of previously inactive, overweight/obese women.

In a controlled randomized, two-group, repeated measures design, 65 healthy, sedentary, premenopausal overweight or obese women were randomly assigned to one of three groups: (a) a control group (C, N=21) that participated only in measurements, (b) a training group (TR, N=14) that participated in a supervised 40-week DoIT workout exercise training program and (c) a training-detraining group (TRD, N=14). During the first 20 weeks, TR and TRD followed exactly the same training protocol. At the end of this period, TR continued training for 20 more weeks whereas TRD terminated training for 20 weeks (detraining). Anthropometric, metabolic, daily nutritional intake, habitual physical activity and performance measurements were performed in all groups at baseline, at 20 weeks and 40 weeks.

Inclusion Criteria:

• (a) were sedentary (<7,500 steps/day; VO2max <30 ml/kg/min), b) premenopausal women aged 30-45 years, c) were overweight or obese class 1 (BMI=25-34.9 kg/m2), d) were non-smokers for ≥6 months before the study, e) not following a diet intervention or using nutritional supplements/medications before (≥6 months) and during the study, f) had no weight loss greater >10% of body mass ≤6 months before the study, g) participated in ≥80% of total exercise sessions, and h) had no symptoms of depression.

Exclusion Criteria:

• a) a recent febrile illness, b) history of muscle lesion, c) lower limb trauma, d) signs, symptoms or diagnosis of serious health complications or physical disability or other medical condition compromising safe participation in exercise training.