Despite surging obesity numbers in the U.S., a new survey finds that just one out of 10 Americans say their diet is unhealthy.

The survey, conducted by Consumer Reports, also found that while four in 10 admitted being "somewhat overweight," just 11 percent said they were very overweight or obese — a direct contradiction of previous weight measurements taken by researchers at the Centers for Disease Control and Prevention, which show that 68 percent of Americans are overweight or obese.

"There does seem to be a disconnect" between reality and the answers most of us give when asked questions about our diet, how much exercise we get and our weight , said Molly Kimball, a registered dietitian at Ochshner's Elmwood Fitness Center in New Orleans.

Not as healthy as we think

Part of the disconnect, Kimball said, comes from the way foods are marketed to us.

"So many people think that what they're eating is healthy — diet frozen dinners, fat-free ice cream, 100-calorie pretzel packs. Or they say,  'I never eat fast food,' but that doesn’t mean they're not eating a lot of other unhealthy things," she said.

In her practice, Kimball said, people tell her all the time that they don't understand why they're not losing weight, because they believe they're eating healthy foods.

For a reality check, people should check the ingredients in their food, she said.

"Skip the front of the package, and turn it over," Kimball told MyHealthNewsDaily. Some granola bars have rolled oats as their first ingredient, others list sugar, she said.

According to the survey, 60 percent said they eat the recommended five or more servings of fruit and vegetables every day or most days.

'If that's true, that's spectacular," said Deborah Enos, a certified nutritionist in Seattle. "But if you look at more studies, that's not what we're seeing."

Part of the problem, Enos said, is that "we really don't have an idea of what a portion looks like. We tend to under-portion the good stuff, and over-portion the bad stuff." In reality, a portion is the size of your fist, she said.

And the survey found that the most commonly eaten vegetable was lettuce or salad greens — 78 percent of respondents said they eat a serving a week.

"We take iceberg lettuce, with 600 calories of blue cheese dressing, and call it a salad," Enos said. But such "vegetables" don't provide us with healthy nutrients.

Some people also think they’re getting a serving of fruit or vegetables when they're not, Kimball said.

"People may think that fruit drinks or gummy snacks may be counted sometimes," she said. "And we feel noble when we eat something like that, like what we’re doing is healthy."

Got a sweet truth?

Half of survey respondents said they limit their daily intake of sugar.

"Sugar is the No. 1 health challenge we're fighting in this country," Enos said. "People have no idea what's an appropriate amount."

Part of the problem, she said, is that the sugar content of food is given in grams, and most people don't have a sense of the size of a gram.

And because sugar is the only element of food for which there's no "daily recommended" amount given on the back of food labels, most people don't know how much is too much, she said. Women should limit their intake to 40 grams a day, and men to 50 or 60, she said.

Kimball said that "limiting" your intake doesn't necessarily mean you're eating a healthy amount.

"If you have it less than you want it — even if you want it a lot — then you're limiting your intake." Such self-imposed limits can lead us to feel we're being healthier than we really are, she said.

And people get a lot of sugar from foods that they don't consider to be sweets, Kimball said. Breakfast cereals are common culprits.

"Or take yogurt – a carton of low-fat yogurt can have 33 grams of sugar," she said. "That might jack up the sugar intake, but in their minds, that's not 'sweets.'"

A nation of exercisers

Most survey respondents reported they get an hour of moderate exercise every day, and 31 percent rated themselves as "very active."

In general, it's harder to be dishonest with ourselves about how much time we spend exercising than it is to fudge on our eating habits, Kimball said. "But perception of exercise intensity can be fudged."

"A stroll may feel like moderate exercise," to some, she said.

Enos said that she would estimate the true number of people who get an hour of moderate exercise every day to be closer to 5 percent. "People really overestimate their physical output," she said.

The weight-loss commandment, Enos said, should be "Thou shall not kid thyself."

"People aren't malicious – they're not trying to lie," she said. "But as a country, because our potions are so out of control, we just kind of blow it."

The report was based on the results of a nationally representative sample of 1,234 U.S. residents age 21 and older, and was conducted by Opinion Research Corporation.

Pass it on: A recent survey found that most of us think our diets are healthy. Nutritionists say this shows we have hard time figuring out what's really healthy.

Follow MyHealthNewsDaily managing editor Karen Rowan on Twitter @karenjrowan.