There isn't any convincing evidence showing fat loss causes metabolic damage; however, observations are more indicative of reversible adaptive thermogenesis.
While it's contrary to a lot of popular fitness culture, the gym isn't the only place where you can lose weight, build muscle, and improve your performance.
An 8-minute, no-equipment workout that actually works - sound like a gimmick? Researchers reviewed the literature on bodyweight exercise and came up with this new circuit.