Do I need to have a re-feed?
Yes you do, as it will:
Increase thyroid hormone output
When in a caloric deficit, underfed individuals produce less T3 and T4, which are both important thyroid hormones that play roles in the regulation of metabolic rate. A re-feed meal is used, in part, to increase these hormones.
Increase 24-hour energy expenditure.
A caloric surplus from a re-feed causes the body to up-regulate basal metabolic rate (BMR). Some studies have shown an increase of 9% above baseline and it’s hypothesised that more is actually possible.
Increase serum leptin levels.
Leptin levels drop while we’re in a caloric deficit (lasting as little as 72 hours), and a periodic bump in leptin coming from a re-feed has several benefits: including increased thyroid output, increased energy expenditure and BMR, and overall increased thermogenesis.