Although all foods contain calories, some foods take so much energy to digest that your body actually burns up the calories from them in the process of consuming them.  These are known as Zero Calorie Foods. Still other amazing foods take so much energy to digest that you actually lose weight by eating them.  These are known as Negative Calorie Foods. So, "negative-calorie food" is a bit of a misnomer in that all foods contain calories.  Instead, it just means that you expend more calories eating these foods than the calories they deliver to your body.

How do these foods keep you full?

When your stomach senses it is physically full, it will trigger your brain to stop eating. This is why the simple act of drinking a glass of water before each meal has been used as a weight loss strategy.  Eating an apple before each meal also works in much the same way – filling your stomach with water, leaving less room for everything else. 

The common property among all negative-calorie foods is that they all contain a lot of water locked in a fibrous matrix.  The more water you consume in your foods, the more quickly you'll feel full and stop eating.  By eating foods that burn more calories than they contain, you can get a jumpstart on weight loss goals you may have for a healthier you. This quick jumpstart can give you the encouragement and confidence you need to continue making healthy choices.

Best negative-calorie foods:

1. Celery

• One cup of celery contains only 19 calories.  It takes far more than 19 calories to prepare, eat, digest and eliminate this one cup of celery, and that's what qualifies it as a negative-calorie food!

2. Lettuce, onions and greens

• Lettuce is basically just water locked into a vegetable matrix.  One cup of typical iceberg lettuce contains just 8 calories. Much the same is true with onions, which contain only 64 calories per cup and yet deliver an amazing assortment of anti-cancer nutrients and immune-boosting medicine.  While lettuce by itself is a negative-calorie food, salad dressing is mostly definitely NOT.

3. Kelp noodles

• Eating noodles is not normally known as a way to lose weight, but kelp noodles are made out of sea kelp, and they're packed with water.  Kelp noodles contain just 6 calories per serving, and yet they take up a lot of physical space in your belly, contributing to that "full" feeling that reminds you to stop eating.

4. Pickled foods

• Pickles are, of course, made from cucumbers, and cucumbers are themselves a "negative-calorie food" because they're so sparse in calories.  One cup of cucumbers contains a mere 16 calories.  When picking up pickles however, you have to watch out for the sugar content in some brands, and keep your choice healthy.  Kimchi and raw sauerkraut are also negative-calorie fermented foods.  These fermented veggies areactually good for your digestive tract because of all the probiotics they contain.

5. Grapefruit

• Grapefruit technically isn't a negative-calorie food, but it's still fairly low in calories, delivering only 74 calories per cup.  Grapefruit contains naringenin, an antioxidant derived from the bitter flavor of grapefruits, which triggers the liver to break down fat.

Here are some more awesome negative/low calorie foods to help you lose weight and keep it off:

• Asparagus                               - Cauliflower                                - Peach

• Apples                                     - Garlic                                          - Pineapple

• Beet                                         - Green beans                              - Radish

• Blueberries                             - Honeydew                                 - Raspberries

• Broccoli                                  - Hot chili peppers                      - Strawberries

• Cranberries                            - Lemon/lime                               - Tomato

• Cantaloupe                            - Mango                                        - Tangerine

• Carrots                                   - Orange                                       - Turnip

• Chicory                                   - Papaya                                       - Watermelon

• Zucchini