The benefits of eccentric (ECC) training on fat mass (FM) remain underexplored. We hypothesized that in obese adolescents, ECC cycling training is more efficient for decreasing whole-body FM percentage compared to concentric (CON) performed at the same oxygen consumption (VO ). Twenty-four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile) were randomized to ECC or CON. They performed three cyclo-ergometer sessions per week (30 min per session) for 12 weeks: two habituation, 5 at 50% VO , and 5 at 70% VO . Anthropometric measurements, body composition, maximal incremental CON tests, strength tests, and blood samples were assessed pre- and post-training. Whole-body FM percentage decreased significantly after compared to pretraining in both groups, though to a larger extent in the ECC group (ECC: -10% vs CON: -4.2%, P < 0.05). Whole-body lean mass (LM) percentage increased significantly in both groups after compared to pretraining, with a greater increase in the ECC group (ECC: 3.8% vs CON: 1.5%, P <0.05). The improvements in leg FM and LM percentages were greater in the ECC group (-6.5% and 3.0%, P = 0.01 and P < 0.01). Quadriceps isometric and isokinetic ECC strength increased significantly more in the ECC group (28.3% and 21.3%, P < 0.05). Both groups showed similar significant VO improvement (ECC: 15.4% vs CON: 10.3%). The decrease in homeostasis model assessment of insulin resistance index was significant in the ECC group (-19.9%). In conclusion, although both ECC and CON cycling trainings are efficient to decrease FM, ECC induces greater FM reduction, strength gains, and insulin resistance improvements and represents an optimal modality to recommend for obese adolescents.

Skeletal muscle generates force by either shortening (concentrically) or lengthening (eccentrically). Eccentric (ECC) exercise is characterized by a lower metabolic demand and requires less muscle activity than concentric (CON) exercise at the same level of exerted force. However, the specific effect of ECC training vs. CON training on lean and fat mass remains underexplored. The first aim of this paper was to review the available evidence regarding the effects of ECC training on whole body and segmental lean and fat mass and, when possible, compare these with the effects of CON training. The second aim was to provide some insights into the main mechanical, physiological, and metabolic adaptations of ECC training that contribute to its effects on body composition. The third aim was to determine the beneficial effects of ECC exercise on health-related parameters in overweight and obese patients. ECC training is an effective modality to improve lean mass, but when matched for load or work, the difference between ECC and CON trainings seems unclear. A few studies reported that ECC training is also efficient at reducing fat mass. By increasing post-exercise resting energy expenditure, modifying metabolic substrate, and improving both blood lipid profile and insulin resistance, ECC training is a potential exercise modality for individuals with chronic conditions such as those who are overweight and obese. Further investigations using standardized experimental conditions, examining not only segmental but also whole body composition, are required to compare ECC and CON trainings.

High-intensity interval training (HIIT) has been suggested as an effective alternative to traditional moderate-intensity continuous training (MICT) that can yield improvements in a variety of health outcomes. Yet, despite the urgent need to find effective strategies for the treatment of pediatric obesity, only a few studies have addressed the impact of HIIT on eating behaviors and body composition in this population. This study aimed to compare the effect of HIIT versus MICT on eating behaviors in adolescents with obesity and to assess if the participants’ baseline dietary status is associated with the success of the intervention. Forty-three adolescents with obesity were randomly assigned to a 16-week MICT or HIIT intervention. Body composition and 24-h ad libitum energy intake were assessed at baseline and at the end of the program. Restrained eating, emotional eating, and external eating were assessed using the Dutch Eating Behavior Questionnaire at baseline. Both interventions led to significant weight, body mass index (BMI), and fat mass percentage (FM%) reductions, with better improvements in FM% in the HIIT group; whereas 24-h ad libitum energy intake increased to a similar extent in both groups. HIIT provides better body composition improvements over MICT, despite a similar increase in energy intake. Restrained eaters experienced less weight loss and smaller BMI reduction compared with unrestrained eaters; higher baseline cognitively restrained adolescents showed a greater increase of their ad libitum energy intake. Novelty HIIT favors better body composition improvements compared with MICT. Both MICT and HIIT increased ad libitum energy intake in adolescents with obesity. Weight loss achievement is better among unrestrained eaters.

A single HIIE session resulted in reduced subsequent energy intake and food reward in adolescents with obesity. Our results also seem to indicate that these nutritional responses depend on the adolescents' degree of obesity with a greater anorexigenic effect observed with higher obesity.