I feel like we're not hearing the whole story. Like the article says, "The local authority said any decision to remove children from their family would not be made solely on the basis of a their weight."
And although I don't normally just believe everything written in the media, I'd tend to say this is the truth, otherwise surely there would be hundreds (thousands?) of families across the UK in the same situation. Social services work hard to keep families together, they provide a lot of support. But in cases where parents aren't taking advantage of the support offered, there's no other option but to remove the children from the parents' care, for their welfare. Taking children out of the family unit is never the preferred option if avoidably, so I tend to think there must be more to this story than what we're reading.