How much weight can you lose eating Big Macs? A new best-selling diet book called "Eat This, Not That" has a Big Mac and a Whopper on its cover, with the happy arrow pointing at the Big Mac under the promise of "Thousands of simple food swaps that can save you 10, 20, 30 pounds — or more!"

Actually, we Lunch Guys are of course the authority here, so we’ll answer the question: Which should you eat, the Big Mac or the Whopper?

Chris: Tom, you and I are the two most vaunted fast-food connoisseurs in the country, yet we have never ever considered the Big Mac a diet food.

This book’s author — David Zinczenko, editor-in-chief of Men’s Health … excuse me, Men’s So-called "Health" — is using the fuzziest, fattiest math of all time.

By his logic, I could lose 100 pounds this year by ordering 50 Big Macs instead of 50 Whoppers. I’ll also be eating one jar of mayonnaise a day ("eat this") instead of two ("not that"). Count that as another 90 pounds of weight lost. By December I’ll be at negative 35 pounds. I’m so excited!

So yeah, this Big Mac vs. Whopper setup on the cover makes zero sense. Besides the flawed premise, the Big Mac is a smaller, whimpier sandwich than the fresh-off-the-grill-flavoring of the meaty Whopper.

The basic McDonald’s patties are, and Ronald must know this, among the most flavorless in all of lunchdom. The Thousand Island dress — oh, sorry, the "secret sauce" — is able to rescue it. And both the look and flavor are iconic and fill me with warmth.

But I usually have to chase my Big Mac with a Double Cheeseburger to fill up in the real world. Add those together and I really should have just had a Whopper.

Tom: I respect the concept of "Eat This, Not That," but really, it’s just dietary common sense — eat the item with fewer calories and grams of fat. The Lunch Guy’s version of "Eat This, Not That" is based on a more important factor, taste. For example, eat a Snickers bar, not a piece of cauliflower.

While Zinczenko’s comparisons are a little more apples to apples than that, just because both the Big Mac and the Whopper with Cheese are the marquee burgers of the chains it doesn’t mean they should necessarily be compared, either. No way one will satisfy you as well as the other.

Now, I occasionally crave a Big Mac as something to go with my McDonald’s fries, but the flavor of the Mac can’t compare to the Whopper with Cheese.

As we learned years ago, the flame-broiled taste of Burger King’s burger outweighs the industrial gimmicky flavor of the Mac with its "special sauce" and redundant middle bun. Sure, the larger diameter of the Whopper makes it harder to handle, but on flavor and freshness alone it’s worth it.

Chris: I’m with you, Tom. For the superior burger taste, the Whopper is the "eat this." For a unique salad-esque burger that’s not as big as it thinks it is — but I love it just the same — the Big Mac is the "eat this."

As for the book, for many reasons, it’s a "don’t buy that."Tom: Yeah, the book is completely unnecessary. If it’s weight loss you are after, my recommendation is simple — Eat this: three-fourths of a Whopper with Cheese, not that: The Whole Whopper with Cheese.