When documentary filmmaker Morgan Spurlock embarked upon a 30-day diet of nothing but McDonald's for his film "Supersize Me," the results of his experiment were none too surprising. Spurlock gained 25 pounds, his cholesterol skyrocketed over the Golden Arches, and his liver was compromised to the point that his doctor compared it to foie gras.

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While Spurlock himself acknowledged that almost no one swings through the drive-through for breakfast, lunch and dinner, let alone every day, his message reminded us of a grim reality we already carry around our waistlines: Eating fast food burgers and fries on a regular basis is not a very nice thing to do to your body.

But that's not me, you say. I'm good. I always get a salad. Yes, it has a little cheese on it, and some croutons. Oh, and I see an egg under there. There, in between the fried chicken strips, right beneath the bacon. But hey, the dressing comes separately, in its own wheelbarrow on the side. And remember: It's still not a Whopper.

The fully loaded salad is a prime example of the fast food industry's response to consumer demand for healthier options. It used to be that the dieter -- and his friends the vegetarian and the health nut -- had but one option to yell from the car window: a plastic tray full of iceberg lettuce topped with a few tomato slices and a scant sprinkling of croutons. For an extra dollar or two, you might add ham cubes and shredded cheese.

But the field of greens has gotten a lot wider in recent years. Most of the top fast-food chains, including burger giants McDonald's, Burger King and Wendy's, each offer a handful of salads big enough to crush your excuse to order a side of fries. No longer restricted to tomato and cucumber slices, they're dressed up with more exotic vegetables, fruit and "regional" flavors whose aim it is to make you forget you're cutting back: Southwestern. Mandarin. Just plain Asian. And if that unfamiliar territory is too intimidating, you can always go back to Thousand Island.

But is choosing a bowl over a bun a no-brainer? Not exactly, according to Dr. Stephen Sinatra, cardiologist and author of "The Fast Food Diet: Lose Weight and Feel Great Even If You're Too Busy to Eat Right."

"A lot of these salads are a false perception," Sinatra says. "They're healthy in general, but you need to go easy on the dressings and some of the other toppings."

For example, a Southwest Taco Salad with reduced-fat dressing from Wendy's has a total of 650 calories and 35 grams of fat. Opt for the honey mustard dressing instead, and the calories climb to 820 – about 30 more than a quarter-pound Double Stack cheeseburger and a small order of fries.

Sinatra says you can navigate that culinary minefield by taking an active role in what's tossed into your lunch. "The fast-food salad can be a blessing or a curse, depending on what you can put in it. If you can do a protein like chicken, that's going to be better than adding a lot of sodium and high-fructose corn syrup from the dressing and the croutons."

Although some salads come pre-made, many restaurants will let you substitute or eliminate ingredients you don't want. Want the chicken in your McDonald's Asian Salad grilled instead of crispy? You've just saved yourself 80 calories. Cut out the meat altogether and you'll save a total of 230 calories -- plenty of leeway for a chocolate chip cookie or a soft-serve vanilla cone.

You'll be in even better shape if you can do a bit of homework beforehand. Almost every fast food restaurant Web site lists ingredients and nutrition information for every menu item, which allows you to compare calories, fat, carbs or whatever other unit dictates whether you deserve dessert. You can also see how specific ingredients take your salad from fab to flab, with our Salad Interactive. Knowing before you walk up to the counter that there is a 310-calorie difference between Burger King's Tendercrisp and Garden salads may be all the information you need to stay on the right track.

So yes, lettuce lovers, it's possible to get a healthy and satisfying meal at that table attached to the floor. But it helps to ground yourself with a little bit of research. "You're still getting a lot of vegetables that are very good for you," Sinatra says. "You just have to be a little careful."

Check Fox5Vegas.com all week for these great diet-related features:

Monday -- Weight-Loss Gadgets Go High Tech

Tuesday -- Can You Find A Healthy French Fry?

Wednesday -- Are Salads Sabotaging Your Diet?

Thursday -- Do Coffee Drinks Fit Into Your Diet?

Friday -- Which Cocktails Fit Into Your Diet?

More Extras:

• 10 Things Your Restaurant Won't Tell You
• Hidden Chemicals In Your Veggies?
• The Perfect Diet?