What happens when we undereat?

What happens when we undernourish and undereat?

This shows up as a lower conversion of T4 into active T3.

If we're not converting our T4 to T3, what are we converting it to? Reverse T3, the brake pedal, the anti-thyroid hormone, the hormone that puts us in survival mode, in hibernation mode like we're a bear in the winter, less energy expenditure, increased fatigue, cold intolerance, hair changes, and plateaued weight.

So what’s the best way out of this?

A calculated gradual renourishing.