It's not actually news, but still ignored by many in the health and fitness community. When the available energy (="energy in" minus "energy expenditure during exercise") drops below a certain threshold the thyroid hormone production breaks downs. And, instead of active T3 the thyroid spills out tons of inactive rT3 to slow down your metabolism.
It's not actually news, but still ignored by many in the health and fitness community. When the available energy (="energy in" minus "energy expenditure during exercise") drops below a certain threshold the thyroid hormone production breaks downs. And, instead of active T3 the thyroid spills out tons of inactive rT3 to slow down your metabolism.