It seems that the answer to this question is at present no--and might remain so until or unless researchers dedicated to elucidating any such relation between leptin and obesity are prepared to subject some population of poor leptin-producing creatures to given organic pollutants, with the aim of determining any measurable effect on leptin capability--a difficult assignment to say the least.
Various studies seeking to confirm the so-called 'obesogen hypothesis' have not unreasonably argued a mechanism of 'endocrine disruption' by certain common organic pollutants, but these are neither comprehensive nor capable of resolving certain paradoxes in the relation between leptin and obesity: notably that leptin levels are routinely observed to be raised in cases of severe obesity. The idea of some derangement in leptin function induced by a local cause therefore becomes attractive in explaining such 'leptin resistance'.
At the same time, it is probably negligent to blame rising levels of obesity merely upon the delinquent appetites and profligacy of affluent people, particularly when certain benefits of fat accumulation, apart from the sheer simple joy of being fed, have been observed: putatively there are diminished rates of neuro-degenerative disorders such as Alzheimer's disease in the mildly obese. (There are various studies drawing such conclusions). Possibly such effects also pertain to the capacity for adipose tissue (AT) to sequester organic pollutants.
Now the respondent to this question has objected to the characterisation of this latter effect as a 'function' of AT when it is clear that this capacity for fat cells to accommodate fat-soluble substances without the necessity for their elaborate discrimination is indeed inherently and innately part of the broader function of AT. The inference of the question itself is in fact that the proliferation of fat cells and fat mass in obese individuals may serve precisely this purpose or function.
Such an assertion requires no troublesome incursion into philosophical or teleological dispute--regarding ultimate cause or intention--nor great excesses of the imagination--that for example we are essentially organic creatures increasingly immersed in the products of oil and other hydrocarbons, themselves loosed from the ancient abeyance of that essential nature--, only the understanding that part of the actual mundane function of fat stores is to hold in continuing abeyance those organic compounds, in particular those which are broadly derivatives of hydrocarbons, which the organism generally is unable either to accommodate elsewhere in its metabolism, as if effectively indigestible food, or successfully to excrete.
It might be emphasised here that the aim of any such inquiry into the relation between organic pollutants and obesity--possibly mediated by a derangement in leptin function--is not of itself to redress any such local cause determined empirically; since realistically such would come only with the inevitable obsolescence of oil and the derivatives of hydrocarbons generally: petroleum, plastics, organic pollutants etc.
The aim is to elucidate the nature of this phenomenon of modern obesity, that at least it might be understood as part of universal necessity, that indeed it must in principle serve some eventual 'evolutionary advantage', not of a family of reproducing organisms--although this is an aspect of it--, but of the universal entirety itself in eternity (which some are emboldened by a peculiar philosophical perspective of the absolute inviolability of such a universal unity to characterise as the 'Unitary Soul', for want of a better description of the singular dynamic and process which must enliven it).
I might add here that there has developed an obsession in the biological sciences with a theory of evolution based not only on the philosophically repugnant idea of 'chance'--which despite the fervour with which such a paradigm is defended cannot of course be quantified in any meaningful way; which incapacity of itself requires that the entire notion be removed from orthodox thinking--, but on the necessity to impute to some detail of formal biological reality an evolutionary advantage conferred by such happenstance (e.g. in the usual view, base mutations) within some limited context, the niche, of which it is in any event merely an aspect, when the ultimate parameters of such advantage, more especially in the greater spatial and temporal context are essentially unknowable.
This is not to dispute the absolute preeminence of an 'evolutionary principle' within universal reality; only to argue that this principle is entirely singular and simply inherent within the fact of existence itself; and most importantly that the ultimate parameters of such a principle can never be objectively discriminated or 'known' by those such as we mere humans entirely immersed within the mechanics of an inviolate universal unity in eternity. No conception of an ultimate 'evolutionary disadvantage' may be formed without the possibility for knowledge of the ultimate intention of such a dynamic universal unity.
And for those who would object that such an 'a priori' postulate of universal unity is improperly metaphysical in character, it would be well for them to remember that the existing scientific and cultural ethos of a blind aimless nature--Dawkinsism--, and the preeminence of 'happenstance' as its primary impetus--which is to say the denial of singular universal cause and intention merely for want of the capacity to discern it--, is only the expression of a passing alternative school of philosophy and its guiding paradigm, essentially that of 'chaotic erroneous nature' groping its cruel meaningless way aimlessly in the eternal darkness awaiting only the guiding hand of Man to render 'order' within it.