Here's what's healthy at McDonald's ... per bite

Some people spend a ton of time trying to cut down on calories. But what if we tried to minimize our calories per bite, instead?

If you consider calories alone, McDonald's Filet-O-Fish sandwich, at 390 calories, seems like a fairly healthy offering. Compare that to a Double Quarter Pounder with Cheese, at 740 calories, and it seems like an even better choice.

But all that changes when you consider the calories per ounce of each item. CNBC selected five random McDonald's menu offerings and looked at how many calories each item had per ounce.

Read MoreIs McDonald's 'broken'? Franchisees are furious

Of the foods scrutinized, the Filet-O-Fish was the least healthy per se, at 78 calories per ounce. The Double Quarter Pounder with Cheese and the Bacon Clubhouse Burger came in at 75.5 and 76.6 calories per ounce, respectively. The healthiest per bite was the hamburger at just 68.6 calories per ounce.

So if you're counting calories, don't just look at the nutritional value. You'll also want to consider how many calories you're getting per bite.