The main objective of this study is to determine if oral supplementation of Citrulline, when combined with HIIT, can produce significant changes in body composition, muscle quality, muscle metabolism and functional capacity in older obese men and women .

The investigators hypothesize that Citrulline combined with HIIT will be more beneficial than HIIT alone which will be more beneficial than citrulline alone which will be more beneficial than placebo alone in obese elderly men and women .

Citrulline is a non-protein amino acid, isolated from watermelon, involved in the urea cycle and an arginine precursor. Participants will take 10g/d of citrulline or placebo (isocaloric).

High intensity interval training (HIIT) is a high intensity aerobic training (30 sec at 85% and up of HRmax + 1min30 at 65-70% of HRmax). they HIIT duration is 30 min/session. HIIT is recognized as beneficial to improve health in human such as Vo2max, body fat or .

Then intervention will be follow during 12 consecutive weeks.

Inclusion Criteria:

1. autonomous (being able to follow the exercise program) and without cognitive impairment (MOCA test ≥21) ;
2. obese status (BMI between 30 and 40 kg / m2 or a waist circumference greater than 102 cm for men and 88 cm for women or fat mass (%; total or androïd or gynoïd) equal or superior to 27% in men and 40% in women;
3. stable weight (± 5 kg) for 6 months;
4. non-smoking and moderate drinkers (max: 15 g/day of alcohol) ;
5. without stroke or history of stroke ;
6. sedentary (less than 2 hours of structured physical activity per week);
7. not being involved in a vigorous exercise program for at least 12 months;
8. can understand French
9. postmenopausal women (without menses since 60 consecutively months).

Exclusion Criteria:

1. to have a metal implant (pacemaker);
2. asthma requiring oral steroid treatment;
3. taking other medication that could affect metabolism or cardiovascular function;
4. taking anticoagulant medication.
5. taking hormonal-replacement therapy (only for women)