Metabolic Flexibility to Predict Lifestyle Interventions Outcomes (MEPHISTO): Protocol for Predictive Validation Study and Randomized Controlled Trial - Monika Ludlova; Kateřina Koudelková; Jitka Pallova; Barbora Koudelkova; Michaela Siklova; Monika Cahova; Tomas Vetrovsky; Michal Steffl; Jan Gojda (JMIR Research Protocols)