Management of Constitutional Thinness Through an Adapted Physical Activity Program, Whether or Not Associated With Food Supplementation. Interventional Study Compared to Matched Controls: NUTRILEAN + Study

The main aim of the present study is to compare the effect of a 12-week physical activity program on body weight gain and body composition changes between normal weight and constitutionally lean individuals. The second objective will be to question the potential additional effect of a protein supplementation coupled to the physical training intervention on body wright and body composition in constitutionally lean women.

After a medical inclusion visit, the participants will realize a maximal aerobic test at the university hospital as well as a body composition analysis, a blood sample will be taken, their resting metabolic rate will be assessed as well as their energy metabolism during a rectangular cycling exercise. Their muscle strength and architecture will be assessed. Their energy intake and eating habits will also be assessed as well as their diet-induced thermogenesis in response to a fixed and an ad libitum meal. Their sleep metabolism will also be assessed using the Dreem technology. Questionnaires will be used to evaluate their daily free living energy intake and accelerometers used to assess their daily physical activity level.

The participants will then perform a 12-week physical activity intervention with 15 of the 30 constitutionally lean one receiving a protein supplementation (randomly assigned). All the measures will be replicated at the end of the intervention as well as 6 weeks after

Eligibility Criteria:
Inclusion Criteria:

Inclusion criteria common to both groups

* Adult women aged 18 to 35, having a stable weight for at least 3 months.
* Body mass index (BMI) ≤ 17.5 kg / m2 (for the "constitutional thinness" group) or 20 kg / m2 ≤ BMI ≤ 25 kg / m2 (for the normal-weighted control group)
* Able to give informed consent to participate in research.
* Affiliation to a Social Security scheme.

Inclusion criteria specific to women with constitutional thinness

* BMI ≤ 17.5 kg / m2
* Weight stable for at least 3 months
* No eating disorder
* No biological markers of undernutrition
* Absence of secondary amenorrhea

Inclusion criteria specific to normo-weighted subjects

* 20 kg / m2 ≤ BMI ≤ 25 kg / m2
* Weight stable for at least 3 months
* No eating disorder
* No biological markers of undernutrition
* Absence of secondary amenorrhea

Exclusion Criteria:

* Pregnant or breastfeeding woman
* Severe progressive disease
* Medical or surgical history judged by the investigator to be incompatible with this study
* Diabetes or any other pathology limiting the application of one or the other trial strategy
* History of cardiovascular and / or neuro-vascular pathology, and / or cardiovascular and / or neuro-vascular risk factors (excluding obesity / overweight)
* Surgical intervention in the previous 3 months
* Taking medications that may interfere with the results of the study
* Regular practice of intense physical activity (more than 3 physical activity sessions per week)
* Regular consumption of tobacco or alcohol
* Special diet
* Abnormal plasma levels of IGF-1, estradiol, free T3, cortisol and leptin (only for the "constitutional thinness" group)
* Persons under guardianship or subjects deprived of their liberty by judicial or administrative decision
* Person in a period of exclusion from another study
* Refusal of participation