Seems viable. Not necessarily due to less effect from the Earth's magnetic field, but maybe centrifugal force? Out at the equator, seems like you ought to weigh a little less just due to the fact that you're more likely to "get flung off" or "lift off" from the Earth as it spins than you are at the poles 8^)
Ever get on one of those manual spinny-merry-go-round-thingies at a playground? It's pretty easy to stay on if you sit in the middle (pole), but the closer you get to the edge (equator) the more likely you are to get flung off.
How's that for a totally non-scientific reason why you should weigh less at the equator than the poles?
Maybe I should submit a white paper to one of these fancy schmancy French scientific journals? Might even get a free international conference trip out of the deal.
It's a scientific reason, and it really holds true. Things do weigh more at the poles than they do at the equator.
The further you are from the center, the greater your instantaneous velocity (directed perpendicular to your radial line to the center). F = mv^2 / r = mr(omega)^2, so force goes like radius.