Well, malnourishment doesn't necessarily equal obesity, but it sure does contribute either to obesity or to an almost-anorexic skinniness. White rice and white bread are the cheapest foods there are... and how far does that go, nutritionally? Not very.
If you are smart, you might be able to thrive on minimum wage by sharing accommodation, being really careful about your food choices, and never seeing a movie. But if you're not capable of minimum wage or if you want to occasionally know what your friends are talking about when they come back from a movie? Too bad... and getting pregnant in such a situation can often be a recipe for disaster.
There is no denying that poverty in third-world countries is worse than it is here. You don't usually see nearly as much deformation from malnutrition here, although some certainly exists. But that actual poverty still exists here at all, and in the shadow of amazing wealth... is a terrible thing.
Perhaps if we eradicated poverty in wealthy countries, we could make a true effort at eradicating it in poor countries, rather than just sending bandaid after bandaid when the problem needs much more than just a bandaid. For one, there would be more people who could afford to help others... and if there was less tolerance of greed on the part of corporations there would be no problem treating medical conditions that contribute to world poverty.