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Purpose: Individuals with constitutional thinness have been presented with a lower muscular energy metabolism at the cellular level but their effective aerobic capacities and exercise-related energy efficiency remains unexplored. The present study compares maximal and sub-maximal aerobic capacities between subjects with constitutional thinness and age-matched normal-weight ones. Methods: Anthropometric measures, body composition (Dual-X-ray absorptiometry), physical activity and sedentary time (GT3x actigraphs), and maximal aerobic capacities (cycling V ˙ O 2peak test) were assessed in 18 constitutionally thin (CT—body mass index < 17.5 kg m−2) and 17 normal-weight (NW—body mass index between 20 and 25 kg m−2) women. Energy efficiency was assessed during a submaximal cycling test and a walking exercise. Results: CT had a lower body mass and body mass index compared to NW. Absolute peak oxygen uptake and maximal aerobic power were lower in CT subjects compared to NW (ES: − 1.63 [− 2.40; − 0.86] and − 1.32 [− 2.05; − 0.58], p < 0.001). V ˙ O 2peak related to body mass was not different between groups. Gross and net efficiency (ES: − 0.78 [− 1.48; − 0.06], p = 0.03 and ES: − 0.73 [− 1.43; − 0.01], p = 0.05) were lower in CT compared to NW during the submaximal cycling exercise. The gross energy cost of walking related to body mass was lower in subjects with CT (ES: − 1.80 [− 2.60; − 0.97, p = 0.05), with no difference for the net one. Perceived exertion was similar between groups in responses to both submaximal exercises. Conclusion: Constitutionally thin women do not show impaired aerobic capacities at moderate to maximal intensities despite lower energy efficiency while cycling and walking at low-to-moderate intensities. [ABSTRACT FROM AUTHOR]

While people with Constitutional Thinness (CT) declare a deep willingness to gain weight, there appetitive responses to energy balance manipulations remain unclear. The present work compares the effect of an acute exercise combined or not with an energy replacement load, on subsequent energy intake, appetite and food reward, between normal weight and women with CT. Anthropometric measurements, body composition (Dual X-ray absorptiometry–DXA) and aerobic capacity (VO2max) were assessed in 10 normal-weight (Body Mass Index-BMI): 20–25 kg/m2) and 10 C T (BMI<17.5 kg/m2) women (18–30 years). They randomly performed i) a resting session (CON); ii) an exercise session (EX); iii) an exercise session with energy replacement (EX + R). Their subsequent ad libitum intake, appetite feelings and food reward were evaluated (Leeds-Food-Preference-Questionnaire). CT showed a lower weight (p < 0,001), BMI(p < 0,001), Fat-Mass (%) (p = 0,003) and Fat-Free Mass (kg) (p < 0,001). CT showed a lower ad libitum energy intake on EX + R compared with CON (p = 0,008) and a higher Relative Energy Intake (REI) on CON compared with EX (p = 0,007) and EX + R (p < 0,001). A lower was observed during EX and EX + R compared with CON (p = 0,006,p = 0,009 respectively) in CT. No condition nor group effect was found for hunger. NW only showed a higher pre-meal fullness on EX + R compared to CON and EX (p < 0,001). Choice (p = 0,030), Explicit Liking (p = 0,016), Explicit Wanting (p = 0,004) and Implicit Wanting (p = 0,035) for taste were higher on EX + R than CON and EX. The decreased EI observed in CT when the exercise-induced energy expenditure is compensated by the ingestion of an equivalent energy load, might contribute to explain the difficulty to increase their energy balance and then induce weight gain. Further studies are needed to better understand their energy balance regulation to propose adapted weight gain strategies. [ABSTRACT FROM AUTHOR]