Does it make sense to have a heavy, fattening meal with Diet Coke?

On some level, it can, but only in the way that Yao Ming is taller than Shaq - they're still so tall that it doesn't even matter, because most normal people won't be bigger than them. Ditto healthy eating vs eating a huge fattening meal with a diet coke - one can be healthier than the other (the huge meal with standard vs with diet) in much that same way - IE none of them are all that healthy, just as neither of the basketballers used in the example are all that small ^_^