'So What Can I Eat?'

Self-discipline is certainly one of the great challenges in sticking to a healthy diet. But many people find it nearly as challenging to keep track of which foods are good for you and which aren't.

Registered dietician Elisa Zied zeroes in on that problem in her new book, "So What Can I Eat?!" She is also a spokeswoman for the American Dietetic Association and joins The Early Show this week for a three-part HealthWatch series. This morning, the topic was fats, and Zied led co-anchor Russ Mitchell through the many different types of fats, pointing out which are the healthiest choices.

The government recommends that Americans get between 20-35 percent of their daily calories from fats and Zied explained why.

"We need fat for many reasons," she said. "First, it provides calories. Second, it provides vital nutrients, including essential fats, which are fats that we need to get from food that we naturally can't create in our bodies. And fat also, on a practical level, adds a lot of flavor, texture and taste to food. It's something we don't want to avoid completely."

Best picks:

Olive oil
Canola oil
Safflower oil
Sunflower oil
Margarine, trans-free, soft, in a tub

These oils contain monounsaturated and polyunsaturated fats, both of which can have heart health benefits if you use them to replace saturated fats, like butter, according to Zied.

Zied recommends sticking to about one teaspoon per serving, and says most Americans should aim for about six teaspoons of healthy oils each day.

1 tablespoon of these counts as 1 teaspoon of oil.

Light or low-fat tub margarine
Light mayonnaise
Salad dressing (low-fat dressing: 2 tablespoons = 1 teaspoon oil)

Although these foods count in the meat/beans food category, they naturally contain oils and some healthful fats. They are also very caloric and energy dense, so stick to small portions.

Nuts: almonds, cashews, peanuts, 2 tablespoons of each
Almond butter: 1 tablespoon
Peanut butter: 1 tablespoon
Fish, especially cold water fish (salmon, tuna, sardines, mackerel) contains healthful omega-3 fats

Butter, shortening, stick margarine, sour cream, cream cheese — these are solid fats that need to be counted as discretionary or extra calories, not as part of any food group recommended by the dietary guidelines. For a 2,000 calorie plan, you can use about 250 of those calories on any foods you like.

To read an excerpt from Zied's book, click here.