Obesity: a drifted adiposity setpoint

Obesity is the lipostat defended at a HIGHER setpoint. A leptin/melanocortin feedback-gain drop raises the defended adiposity, and a sustained positive energy forcing drifts the regulated state up -- a SUB-spinodal drift (crossed = False), so the body actively DEFENDS the elevated fat mass, which is why loss is resisted.

Lipostat node (γ 1.3902). A gain drop of 0.3500 plus a positive forcing drifts the setpoint up without crossing (residual spinodal 0.3306 exceeds the forcing). Shape [V]; defended-setpoint drift vs cited energy-balance data [L]; absolute kg/BMI [O].

Mechanism

leptin/melanocortin feedback-gain drop raises the defended adiposity setpoint; a sustained positive energy forcing drifts the regulated state UP (defended at higher adiposity) -- sub-spinodal drift, not (yet) a basin crossing.

Drift, not crossing

Here the chronic forcing 0.3000 stays below the residual spinodal 0.3306, so the basin is intact but its position has moved up. The body defends the new, higher adiposity -- which is exactly why dieting against a drifted setpoint is opposed by the same machinery that defends temperature.

Implication

Because obesity is a DRIFT, lowering the forcing AND restoring feedback gain can move the setpoint back without needing to re-cross a barrier. The restoration map places leptin re-sensitisation (S1) and appetite-forcing reduction (S2) precisely here.