Shopping for healthy food at a supermarket can be difficult, especially when food labels are often misleading.

In order to trim the fat from your shopping list, Dr. Michael Roizen, author of "You: On a diet," offers tips on which foods to avoid and which to buy.

Eating certain foods cause the body to release a chemical known as CCK (Cholecystokinin), which tells your brain to stop eating.

CCK is a peptide hormone that is released by gastrointestinal system and helps the digestion of fat and protein.

"We're going to show you what foods to eat to get that so you feel full," Roizen told Canada AM Thursday.

The small print

Before putting any food into your cart you must first inspect the label very carefully.

"Whole grains are one of the most important things but there are some things you really want to look at in the label," Roizen said.

The first detail you should look for is the fat content in the product, specifically saturated fat and trans fat.

"If it's got any trans fat, don't buy it," he said, "Why should you age yourself? It causes inflammation."

If the product has more than four grams of saturated fat per serving, you should also steer clear.

The next item on the label you should pay attention to is the amount of sugar per serving.

"If it has more than four grams of sugar, don't buy it. In fact, dump it out of your house. If it's not in your house you won't eat it. Get rid of it!"

The third ingredient to look for is to see if 'whole grain' listed.

Often products are made with enriched flour, which is only the endosperm of the grain.

"They refine out the bran, which has a lot of fiber and B vitamins and the endosperm, which has a lot more of the good nutrients and vitamins in it," Roizen said.

When shopping, look for foods that will help you control your appetite.

"The foods you want that turns on that CCK is healthy fats -- healthy fats like nuts are good for you," he said.

But not all fats will ignite your CCK.

"Things that aren't good for you are butter. It causes inflammation in your body."

Avoid anything that is not whole wheat, no matter how healthy it may appear.

According to Roizen, your body cannot tell the difference between a chocolate bar and pasta.

"Your body thinks they're the same. They're simple sugars. You want whole grains."

Another way to control you appetite is to drink coffee or tea.

"Real coffee and tea have good chemicals in them that say, 'I don't need to eat anything else," Roizen said.

Friday: Canada AM will show you how to find out what kind of taster you are