Microvascular and Metabolic Effects of High-intensity Interval Exercise Training

Microvascular and Metabolic Effects of High-intensity Interval Training (HIIT) and Intermittent Fasting (FAST) in Overweight or Obese, Sedentary Women With Cardiometabolic Risk Factors: HIIT-FAST, a Randomized Clinical Trial

The study investigates the effects of high intensity interval training (HIIT) versus continuous training (CT), combined or not with fasting, on capillary density, microvascular function, cardiometabolic risk markers, functional capacity, and quality of life, in overweight or obese sedentary women with cardiometabolic risk factors. The use of HIIT could promote greater improvements in these parameters than CT. Furthermore, the positive effects of exercise may increase when it is performed in the fasting state, compared to exercise performed in the fed state.

Physical inactivity and increased caloric intake play important roles in the pathophysiology of obesity. Increases of physical activity and modifications of eating behaviors are first-line interventions which, however, are not easily implemented, and lack of time to exercise and difficulties in coping with different diets are common reasons for failure. High-intensity interval training (HIIT) is a "faster" alternative to moderate-intensity continuous training (CT). Conversely, intermittent fasting is also an alternative to more complex diets, as it restricts caloric intake to a specified period of time without major diet composition changes. The combination of HIIT and fasting may therefore provide incremental benefits.

Sedentary women aged ≥ 30 years and ≤50 years, with body mass index ≥25 kg/m2 and cardiometabolic risk factors, will be randomized to HIIT performed in the fasting state, HIIT performed in the fed state, CT in the fasting state or CT in the fed state. Cardiometabolic parameters, anthropometric indices, cardiorespiratory fitness, quality of life and microvascular function (cutaneous capillary density and microvascular reactivity evaluated by laser speckle contrast imaging) will be evaluated before the initiation of the interventions and 4 weeks thereafter.

Inclusion Criteria:

• Female gender
• Age≥ 30 years and ≤50 years
• Premenopausal status
• Body mass index >25 kg/m2
• At least one of the following:

waist circumference ≥80 cm (women); triglycerides ≥150 mg/dl or treatment for this lipid abnormality; High density-lipoprotein cholesterol <50 mg/dl (women), or treatment for this abnormality; fasting plasma glucose ≥100 mg/dl

Exclusion Criteria:

• Any cardiovascular disease, including systemic hypertension
• Diabetes mellitus
• Chronic pulmonary disease
• Any systemic disease or condition that might reduce the adherence or tolerance to exercise or fasting
• Orthopedic or neurologic conditions that might impair exercise training
• Pregnancy or breastfeeding
• Abnormalities elicited at exercise treadmill testing that preclude the initiation of exercise training
• Current engagement in any exercise training protocol