A scheme for considering stellar structure by taking advantage of the quadr
atic theory of gravitation in four-dimensions is proposed, citing the fact
that the possible deviation of gravity in astrophysical systems from the Ne
wtonian inverse square law can be explained through the use of this theory.
A modified Lane-Emden equation is derived by making use of the linearized
static field equation of quadratic gravity and the polytropic equation of s
tate for a fluid. The influence on stellar structure of the additional forc
e included in quadratic gravity is investigated. It is shown that the addit
ional force can be treated as a perturbation of a bound system by solutions
of the modified Lane-Emden equation and an order-of-magnitude analysis.