Capt Claret
Very simply if the total price is different because of a person’s weight and people have between disadvantaged because this, it is grounds for discrimination because in most cases the obesity is either caused by a disability, disease or is a personal attribute and is either covered under the DDA or various State/Territory Anti-Discrimination Laws.
BNEA320
It's actually discriminatory to charge a lighter person the same as a heavier person.
And how have they been discriminated against when the total price is the same? In your example no one is advantaged or disadvantaged. Also the price hasn't been based on weight. It's just a fixed price. If you were to make such a claim it would be you having to explain how a fixed price is discriminatory. In fact the discrimination could be levelled at you because it could be argued you are trying to take a financial advantage over a person because of their weight.