Then it is a lifestyle choice, because they are consciously choosing to be obese.
I really don't buy into this lifestyle choice = conscious choice idea.
Ask any obese person whether they consciously chose to be very fat?
Obesity that isn't strictly genetic or non genetic developmental disorders (epigenetics etc) is the result of many life experiences and choices.
And I believe homosexuality is too. In some ways homosexuality is a sort of reaction against societal conditioning towards strictly defined sexual roles. Basically lots of subtle experiences and decisions compound into a feeling that the reason why you feel different is due to a specific cause eg homosexuality.
The causality is clearly more complex/chaotic than the obesity case, but it is a reasonable hypothesis.
The fact is currently there is virtually no proof that homosexuality is genetic or that it is due to early developmental issues. There have been plenty of hypothesis, some of which have made it to the media, but little that have been confirmed. Is this due to our primitive knowledge of biological science, or simply because the evidence isn't there?
As such, I will certainly change my belief if significant contrary evidence eventuates.
Interestingly, if homosexuality is not considered to be a legitimate lifestyle choice, then that automatically makes it a disease. When given such a status, there will always be those who believe it should be cured. On the other hand, if society recognises that sexuality is not strictly defined and recognises homosexuality as a legitimate lifestyle choice then it is no longer an issue.