This week’s episode of “No Shit, Sherlock” is brought to you by the consumer group Which?, whose analysis of the worthy-looking sandwiches and pasta salads we buy for our lunch indicates that they can can be as unhealthy as so-called junk food.

Today’s Guardian, in its analysis of the analysis, notes that “Caffè Nero’s brie and bacon panini was highlighted as having more calories (624) than a McDonald’s quarter-pounder with cheese (518)”.

All that surprises me about this is that we’re expected to find it surprising in the first place. Break down the two sandwiches into their constituent parts – bread, red meat and cheese – and there’s no meaningful difference. So what would possess anyone to imagine that the brie and bacon panini – or panino, for all you Italian grammar pedants out there – would be somehow healthier than a burger comprising much the same stuff?

Other findings reported in the Guardian article are similarly illuminating. Mayonnaise – a mixture of a little egg and vinegar and an awful lot of oil – is quite high in fat. Adding a packet of crisps and a bottle of Coke to your lunch will increase its calorie count.

The Which? report, and the fact that it appears to qualify as news, say little we didn’t already know about packaged food, but a great deal more about our relationship with brands. To be fair to Caffè Nero, I’m not sure they’ve ever advertised the offending panini as some kind of healthy option. But if you perceive McDonald’s as representing the very worst of everything, it’s only logical that you’d imagine anything with an M&S or Pret a Manger logo to be less bad for your physical and moral well-being.

The only problem with this is that it’s patent nonsense, and always has been. If we accept the vices and virtues of capitalism in all its other aspects, why would food be the exception? Everyone in the business of selling food, be it McDonald’s, Caffè Nero or your local kebab shop, wants you to buy their wares. Within the scope of the brands they’ve defined for themselves, they’ll try to sell you what you’re most likely to buy. And they don’t much care if you get fat, develop type 2 diabetes or die; unless, of course, their brands become widely associated with those things, which might affect their sales.

We overconsume certain types of food – meat, salt, fat, refined sugars and starches – because we like the way they taste. So it’s hardly surprising that our convenience foods, from the Big Mac to the mayo-laden chicken pasta salad, are packed with these food types. Any food vendor could change the composition of its products tomorrow to include less of any or all of them. But we’d enjoy them less, so we’d be less inclined to buy them; and so it would be commercial suicide.

Of course, the holy grail of food marketers is to convince us that we’re eating better when in fact we’re doing nothing of the sort. And if we really are willing to believe that one red meat and cheese sandwich is fundamentally healthier than another, it looks like they’re on to a winner. But if we pause for even a moment to assess what we’re about to eat, we can work out that the difference exists purely in our imagination.

Which? executive director Richard Lloyd has stated that he wants “all manufacturers to adopt traffic-light nutrition labelling […] so consumers can see exactly what products contain.” And who knows, maybe that would have some impact on what we buy; but I have my doubts. What I can say with rather more certainty is that the big vendors would do as they’ve done with all previous legislation to give us improved information about the food we buy: first, they’d resist it, then they’d circumvent it. (For a longer and more considered view on this particular topic, see this piece I published last year.)

Ultimately, if we genuinely do want to eat better – and I’m yet to be convinced we really do – the solution will be found not on food labels but through our senses, thoughts and actions. You don’t really need to be told that Subway bread is chock-full of sugar; you can taste it. (If you walk within a few yards of one of their outlets, you can even smell it.) Nor should you need a Which? report or Guardian article to tell you that most processed food contains a lot of not-so-good stuff; buying it will always represent an act of blind faith, even if the labels end up 90% covered in nutritional information.

As was always the case, the best way to be confident in what you’re eating is to buy unprocessed (or less processed) food and prepare it yourself. Your lunchtime pasta salad might contain almost anything; an orange, labelled or otherwise, is still an orange.

How much importance you place on all this is, of course, entirely up to you. Few of us have the time or inclination to eat the “right” thing all the time. And I’m certainly not averse to the odd double cheeseburger. But if you’re as surprised by today’s news as Which? seem to expect you to be, it might be time for a little more lateral thinking and a little less brand loyalty.