HOUSTON -

The health food business is booming in Houston. Since 2009, a handful of chains have cropped up to counter the fast food industry.

These restaurants sell fresh, low-calorie meals to go for busy people who want to eat healthy but don't have the time to cook. It's advertised as prepared food that's good for you and tastes good, too.

Does that sound too good to be true? Local 2 Investigates had nine meals tested to find out if the calories and fat advertised are accurate.

We shopped at Houston's three biggest health food chains: My Fit Foods, Snap Kitchen and TruMeals. We purchased three items at each location. We made note of the calories and fat on each dish, then packed them up and sent them to an independent lab for testing.

"A little bit of fudging either way is allowed by the FDA," explained Registered Dietician Roberta Anding of Texas Children's Hospital.

Anding said calories are not an exact science. It's why the Food and Drug Administration allows manufacturers to be over or under the stated calories on nutrition labels by 20 percent.

"In order to get it exactly right, it would always need to be a 4-ounce chicken breast," said Anding. "It would always need to be an exact half cup of rice."

So how exact were the meals we tested?

Four out of nine had higher calories and fat than advertised. Of those, all four missed the mark by more than 20 percent. Another four meals actually had fewer calories and fat than the labels claimed. One was almost exact, with just a 6-calorie difference.

"You have to look at this and say, 'At the end of the day, or at the end of the week, does it all average out?" explained Anding. "In the end, it usually does."

But when you consider the recommended daily calories for the average woman hoping to lose weight is just 1,500, those differences Local 2 Investigates discovered don't seem so small.

"If I'm having three meals and they're all over by 100 calories, now I've eaten 300 calories more than I thought," reasoned Anding. "And I could be scratching my head and saying, 'Why aren't I losing weight?'"

"Real people are cooking this food," My Fit Foods nutritionist Meg McCall said. "This is not manufactured food."

McCall said their cooks try to be 100 percent accurate, but human error accounts for the differences. One heaping scoop instead of a level one may be all it takes to throw the calories off kilter.

"Transparency is a key component in the process," said Snap Kitchen's dietician Andrea Hinsdale, responding to the test results we shared.

Both companies said the more telling numbers are the customers who are losing weight and getting healthier by eating their food.

"We help people lose weight," said McCall. "We help them feel better. We help with whatever their goal is."

Local 2 Investigates tested three different meals from each business. A test by the FDA would have sampled many of the same type of meal from each location.

My Fit Foods sent us the following statement after our interview:

"Although we wish the analysis of the three meals would have followed FDA protocol for accurate testing and information, My Fit Foods appreciates any and all information that helps us improve our business and service to our customers.

We have recently undergone a full review of all recipes and have updated menu items from customer feedback, visual appearance and updated ingredients. This information is available on our website at http://www.myfitfoods.com."

TruMeals was the only business in our test that didn't return our calls or emails. Ironically, the only meal we tested whose advertised calories and fat was almost a perfect match to what our tests showed came from TruMeals.

Below is the list of every meal we tested, the stated calories and fat on the nutrition labels along with what the calories and fat an independent lab found in the same meals.

My Fit Foods

Lean Lemon Turkey Meal (medium)

Label: 340 calories 12g fat

Actual: 440 calories 17g fat -- 29 percent more calories

Good Morning Sunshine (medium)

Label: 360 calories 15g fat

Actual: 460 calories 20g fat – 28 percent more calories