Why is it that some foods that make you fat and others don't? This because the foods that cause you to gain weight take very little energy to burn. They are processed almost immediately and usually stored in your body as fat. Foods that make you skinnier are usually foods are harder to digest and therefore speed up metabolism by using up more energy during the digestion.

These foods that speed up metabolism are called "negative calorie foods." Now, these foods do not have some magical properties to just erase the number of calories in your body and write a new, lower number. Wouldn't that be nice?

What really happens is that these foods make your body work harder while digesting them. Foods like this already possess a lower amount of calories to begin with but are also full of fibrous materials that the body cannot easily break down, therefore it uses more energy.

What this means is that your body creates more energy to turn the food into fuel (burns more calories) than the total amount of calories in the food to begin with. Thus, there is a negative amount of calories; you've used enough energy to burn off the calories of the food you ate PLUS some! Your body then has to use stored fat to convert into energy to finish the digestion process. In turn, you speed up your metabolism.

Did I confuse you? Here is another example. I'll keep it simple.

Say you eat a half of a grapefruit that contains 40 calories and it takes your body 90 calories to digest it. You have used all 40 of the grapefruit's calories PLUS 50 calories from stored fat resulting in an overall calorie loss.

It works the opposite for most of us. We eat a decadent chocolate brownie that contains 175 calories but our body on uses 75 calories to digest it. We now have GAINED 100 calories to be stored as fat for later use. Problem is, unless you are exercising regularly to actually USE those calories, they're going to just sit there around your waist accruing like the interest of a retail credit card until one day it will hit you and you'll wonder, "where did this thing COME from?!"

I have included below, a comprehensive list consisting of mostly fruits and vegetables, which should help get you started with negative calorie foods that help to raise your metabolism. Use these along with your regular menu items and you should start to see and feel some noticeable changes in your body.

Salads are always a good choice. Create your own using lettuce, tomato, onion, carrots cucumber, broccoli, cauliflower and radish. Be sure not to load up on the salad dressing. You can add toppings like raisins or sunflower used in smaller quantities.

Steamed vegetables make a healthy side dish using foods like broccoli, green beans, spinach, zucchini, carrots, onion, cauliflower, cabbage and asparagus. You can add garlic if you choose.

A low fat fruit cup is a healthy dessert. Try using strawberries, cranberries, mango, orange, pineapple, raspberries, tangerine, papaya, grapefruit, cantaloupe, honeydew, apple slices, and watermelon.

Smoothies are one of my favorites. You can use any combination of the fruits above mixed with ice or low fat frozen yogurt. Remember, you can also use these fruits in their juice form but fresh-squeezed is healthier than juice from concentrate.