Foods that wreck diets

We all mean well, especially when we're watching our weight. But some of the foods we think are helping us shed pounds, may actually be keeping them on.

Choosing a smoothie over a shake sounds like a good plan, but you have to be careful, said Kristin Kirkpatrick, a registered dietitian at Cleveland Clinic's Wellness Institute:.

"A large smoothie at a popular store can be anywhere from 800 to 1200 calories, and for some women that are trying to lose weight, that could be their total allotment for the day," she says.

If you make your own smoothie, Kirkpatrick says you can control what goes in and keep the calorie count down.

It may surprise you, but many fat-free foods can wreck a diet, as well. Most fat-free foods are packed with sugar and very little nutrients.

Fiber bars sound healthy, but can also be high in sugar.

"Many of these fiber bars, these protein bars are candy bars in disguise," Kirkpatrick says. "Fiber is added in through 'inulin' but usually the first or second ingredient could be sugar."

Kirkpatrick says low-calorie frozen meals can also be dangerous. They're easy to make, but contain lots of sodium, so they must be eaten in moderation.

Even trail mix can derail a diet plan, if you don't watch portion-sizes, she says.

"Trail mix is healthy from the standpoint that it probably has raisins or nuts or dark chocolate- all healthy things, but all of those things are also very high in fat, which means they are very high in calories."

Kirkpatrick recommends making up your own bags of trail mix, one-quarter cup at a time, and storing them in plastic baggies.