Although High-intensity interval training (HIIT) has shown its effectiveness in improving body composition, cardio-respiratory fitness and lipid profile in obese adults, evidences remain limited in overweight/obese youth. This study was conducted to investigate the effect of a 12-week HIIT program without caloric restriction on body composition and lipid profile among young overweight/obese men. Twenty healthy obese youth were randomly allocated into two groups; experimental group (HIIT) and control group. The HIIT program consisted in 3 exercises sessions per week (30 sec of work at 100% maximal aerobic velocity [MAV]) interspersed by 30 sec of active recovery at 50% MAV, starting by 15 repetitions to reach 27 by the end of the program. Aerobic capacity (MAV and maximum oxygen uptake [VO2max]), body composition (body mass index [BMI], waist circumference [WC], and fat mass percent) and lipid profile (triglycerides [TG] and total, high-density lipoprotein [HDL] and low-density lipoprotein [LDL] cholesterol) were determined before and after the HIIT program. Following 12 weeks of HIIT, WC, BMI (P<0.01), and fat mass percent (P<0.05) were significantly decreased. MAV and VO2max were significantly improved in the HIIT group, only. Total cholesterol (P<0.05) and TG (P<0.05) decreased significantly in the HIIT group, while LDL and HDL cholesterol levels remained unchanged in both groups. HIIT may be particularly useful in overweight/obese youth to improve body composition, aerobic fitness and lipid profile.

To examine the effects of short high-intensity interval training (HIIT) on body composition, physical performance and plasma lipids in overweight/obese compared to normal-weight young men. Nine overweight/ obese and nine normal-weight men (control group) aged 17 to 20 years underwent a HIIT...

Background: Ghrelin is a peptide hormone predominantly produced by the stomach. It exerts a wide range of functions including stimulating growth hormone release and regulating appetite, food intake, and glucose and lipid metabolism. Since physical exercise affects all these aspects, a particular interest is accorded to the relationship between ghrelin and exercise. This systematic review aimed to summarize the current available data on the topic for a better understanding of the relationship. Methods: An extensive computerized search was performed in the PubMed and SPORTDiscus databases for retrieving relevant articles. The search contained the following keywords: ghrelin, appetite-related peptides, gastrointestinal peptides, gastrointestinal hormones, exercise, acute exercise, chronic exercise, training, and physical activity. Studies investigating the effects of acute/chronic exercise on circulating forms of ghrelin were included. Results: The initial search identified 840 articles. After screening, 80 articles were included. Despite a heterogeneity of studies and a variability of the findings, the review suggests that acute exercise suppresses acyl ghrelin production regardless of the participants and the exercise characteristics. Long- and very long-term exercise training programs mostly resulted in increased total and des-acyl ghrelin production. The increase is more noticeable in overweight/obese individuals, and is most likely due to weight loss resulting from the training program. Conclusion: The review suggests that exercise may impact ghrelin production. While the precise mechanisms are unclear, the effects are likely due to blood flow redistribution and weight loss for acute and chronic exercise, respectively. These changes are expected to be metabolically beneficial. Further research is needed for a better understanding of the relationship between ghrelin and exercise.

Objectives: To investigate the effects of 12-week high-intensity- (HIIT) vs. moderate-intensity-interval training (MIIT) on thyroid stimulating hormone (TSH) and thyroxine (T4) and insulin-resistance in overweight/obese adolescent girls. Methods: Twenty four adolescent girls (age 16.5±1.36 yrs) were randomly allocated into three groups: (1) HIIT (2 blocks per session of 6–8 bouts of 30 s runs at 100–110% maximal aerobic speed (MAS), with 30 s active recovery between bouts at 50% MAS; n=8), (2) MIIT (2 blocks per session of 6–8 bouts of 30 s runs at 70–80% MAS, with 30 s active recovery between bouts at 50% MAS; n=8) and (3) control group (no exercise, n=8). Each training groups engaged in three sessions per week during three months. Anthropometric parameters, aerobic capacity, homeostasis model assessment index for insulin resistance (HOMA-IR) as well as plasma TSH and T4 levels were assessed in all subjects before- and after-training. Results: Following both training programs, body mass, body mass index Z-score, waist circumference and body fat decreased, while aerobic capacity increased. However, TSH and T4 concentrations decreased only after the HIIT (−30.47%, p<0.05, ES=1.42 and −12.86%, p<0.05, ES=1.18; respectively). The HOMA-IR decreased in both training groups (−26.25%, p<0.05, ES=1.87 for MIIT and −21.72%, p<0.05, ES=2.14 for HIIT). Conclusion: Twelve weeks of HIIT was effective in reducing circulating TSH and T4 levels, unlike MIIT, in overweight/obese adolescent girls. These findings indicated that the stimulation of pituitary-thyroid function is more sensitive to training intensity than training duration. Further studies are needed to confirm this conclusion.

To compare the effects of 12 weeks of high-intensity interval training (HIIT) versus moderate-intensity interval training (MIIT) on hematological and inflammatory markers in youth females, 38 overweight/obese females (16.4±1.0 yrs.) were randomly assigned to HIIT (2×6–8 repetitions of 30 s at 100–110% maximal aerobic speed (MAS), with 30 s active recovery between repetitions at 50% MAS; n=13), MIIT (2×6–8 repetitions of 30 s at 70–80% MAS, with 30 s active recovery between repetitions at 50% MAS; n=13), and a control group (CG, no intervention; n=12). Body composition, blood pressure, maximal heart rate, hematological and inflammatory markers (C-reactive protein [CRP], and erythrocyte sedimentation rate [ESR]) markers were assessed in all groups before and following the training program. Results revealed a significant (P<0.05) interaction effect for body composition, systolic blood pressure (SBP), MAS, maximal heart rate, and CRP. Within-group analyses for the HIIT and MIIT groups showed significant improvements in body mass (P=0.009 and P=0.025, respectively), BMI Z-score (P=0.011 and P=0.028, respectively), and MAS (P<0.001 and P=0.011, respectively). The HIIT program showed a significant decrease in body fat (P=0.002), waist circumference (P=0.002), maximal heart rate (P=0.003), SBP (P=0.001), and plasma CRP (P=0.004). In both groups, no significant changes were observed in ESR and hematological markers after intervention. No variable changed in CG. HIIT was the effective method to manage cardiometabolic health and inflammatory disorders in obese youth.

Background/Objectives: Despite the abundant body of evidence linking high-intensity interval training (HIIT) to cardiometabolic markers, little is known about how HIIT affects liver enzymes, particularly in obese adolescents. This study aimed to investigate the effects of HIIT on metabolic dysfunction-associated steatotic liver disease (MASLD)-related biomarkers in overweight/obese adolescent girls. Methods: Thirty-three overweight/obese adolescent girls (age, 17.0 ± 1.15 yr.; body mass index, 33.3 ± 4.77 kg/m²) were randomly assigned to HIIT (n = 17) or control (n = 16) groups. The HIIT group participated in a nine-week HIIT program (three times weekly) without caloric restriction. Maximal aerobic speed, body composition indexes, blood pressure, MASLD-related biomarkers [liver enzymes (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), plasma lipids, uric acid, platelet count, and homeostasis model assessment index for insulin-resistance (HOMA-IR)] were examined at baseline and after the intervention. Results: Significant “time × group” interactions were found for body composition indexes, systolic blood pressure, maximal aerobic speed, liver enzymes ALT and AST, plasma lipids, glucose, and HOMA-IR. The HIIT program resulted in an increase in maximal aerobic speed (p = 0.035) and a decrease in body composition and plasma lipids (p < 0.01), systolic blood pressure (p = 0.011), ALT (p = 0.013), AST (p = 0.012), and HOMA-IR (p = 0.01), but no significant changes in uric acid and platelet count. None of these markers changed in the control group. Conclusions: HIIT resulted in an improvement in MASLD-related biomarkers. HIIT could be an effective exercise therapy to prevent and reverse MASLD in adolescents with obesity.