The Jetsons were onto something with their meal-in-a-pill diet. Nowadays, the array of food bars is daunting: Dozens of brands promise to curb your hunger, provide your daily nutrients and even replace an entire meal without scrimping on taste. While processed food will never live up to the real thing, the promise of the perfect bar lured us in. Just to see what would happen, I ate only nutrition bars (except for a sensible dinner each night—I wanted to keep living) for a week.

Day 1
My first challenge was navigating breakfast without my daily bagel. The LUNA Sunrise (Strawberry Crumble, 99¢, at Whole Foods Market, 95 E Houston St at Bowery, 212-420-1320) was a great alternative—it satisfied my sweet tooth, plus at only 170 calories, it was a healthier option. So far, so good.

I’ve never heard the words free lunch whispered in the Time Out offices, and yet I found myself in a staff meeting surrounded by communal pizzas. I spent the meeting staring at my coworkers like they were giant Big Macs and I a crazed Hamburglar. Resigned, I chowed down on a Slim-Fast Optima bar ($1.69, at Duane Reade, various locations throughout the city, go to duanereade.com for more info), which promises to curb hunger for up to four hours. But it didn’t make me any less tempted to lick the greasy cardboard of the empty pizza box.

Day 2
I’ve never been one of those people who “forgets to eat,” but I can relate to being too busy to sit down and have a meal. Most lunches are spent at my desk, where I often splatter papers with salad dressing or ketchup. It was nice to have an alternative that didn’t leave stains (South Beach Meal Replacement Bar, Chocolate Crisp, $1.99, at Food Emporium, locations throughout the city), but that still didn’t make up for the fact that my stomach was in an uproar, my head was pounding and concentrating on my work seemed impossible.

Day 3
Hi. My name is Rachel and I am a candyholic. Walking past the vending machine was like trying to sober up in Vegas—even though I know the Luna Bar I opt for (Nutz Over Chocolate, 99¢, at Whole Foods Market, various locations throughout the city) is a better choice than the junk I normally inhale midday. The sound of my coworkers chewing seems to be magnified; all I hear are chip bags opening, smoothies being slurped and greedy lips smacking in delight. I feel like I’m about to have one of those manic I “gotta have my Pops” cereal moments. I’m tired, my stomach is still not pleased with this little experiment, and I contemplate giving up.

Day 4
I decide to stick it out for one more day—just 24 hours short of my original goal. I’m so repelled by the thought of eating another nutrition bar that I’d rather go hungry, which I do. I try eating a few, but can’t stomach them.

The Results:
Calories consumed (not including dinner), number of bars consumed and money spent each day:

Day 1: 820, 4 bars, $6.33

Day 2: 807, 5 bars, $7.75

Day 3: 720, 4 bars, $5.36

Day 4: 430, 3 bars, $2.73

Pounds lost: 4

Conclusion
So what did this experiment teach me? Dr. Carol Forman Helerstein, who has a Ph.D. in nutrition, confirmed what I already knew. “Nutrition bars should be used as a tool in your arsenal of healthy eating, not as a replacement for every meal, every day,” she says. Still, any nutrition is better than no nutrition. If you don’t have time to eat, or you know you’re going to skip breakfast, “then you would be a good candidate for a nutrition bar,” Dr. Helerstein explains. “But anything that nature makes is better, since that is what our body is meant to break down.”

All bars are not created equal
Make sure you read the label: Dr. Helerstein says you should avoid products that are high in sugar, hydrogenated fat or corn syrup. “Also stay away from artificial sweeteners—they are toxic to the brain and give you cravings, so it counteracts your original goal, which was to not eat more,” she says. You should gravitate toward bars that are chock-full of good antioxidants, which are usually found in fruits and veggies and support your immune system. Also look for fiber, omega-3 fatty acids, whey protein, and xylitol and agave (which are healthier alternatives to white sugar).

How does a guy fare in our extreme experiment? We put one to the test.

The best of the bunch

You Bars, box of 12 for $40, youbars.com
You Bars are handmade according to your preferences—you pick and choose the ingredients. Each package is plastered with a customized label, such as “Emily’s BARmitzvah” or “Tommy’s Bar Code.”

LUNA Sunrise and LUNA Bars, 99¢, at Whole Foods Market, various locations throughout the city, go to wholefoods.com for more info.
LUNA was definitely the best-tasting bar I had all week. While it’s not meant to be a meal replacement, it’s an excellent option to curb hunger during the day and is good to have around when the vending machine starts calling your name at 3pm.

Slim-Fast Optima Meal-on-the-go bars, $1.69, at Duane Reade, locations throughout the city.
Throw one of these meal-replacement bars in your purse to help you avoid fast-food pitfalls. They offer built-in calorie and portion control in decadent flavors like Rich Chocolate Brownie, Chocolate Cookie Dough and Crispy Peanut Caramel.