Water has no calories. Celery (with no dipping sauce) qualifies, because even though it does contain some calories, the effort of chewing it will burn more calories than the celery contains. Some diet sodas have zero calories.
There are low calorie foods such as lean cuts of meat, beans, and legumes are some of the high protein low calorie foods that would work good in a low calorie diet.
It depends on the type of food. Some foods are calorie dense while others are low calorie.
Everything. Calories are a myth.
carboydrates, just not fatty foods, which increases bad cholesterol
You can find the best foods for a 2000 calorie diets in books mostly. You can also find some articles about this diet in magazines and newspaper sometimes.
LiveStrong has a list of low-calorie foods. They include greens, mushrooms, vegetables, fruits, rice cakes, popcorn, and things that are labeled as "reduced fat".
Foods
Zero calorie foods are good for someone who is on a diet and are counting calories. It really depends on the diet you are on. While zero calorie foods might be low in calories some are high in carbs. If you are on a low carb diet, such as South Beach, this might effect your diet and do the opposite.
You may find some of these negative calorie food chart at these sites. They are fasting.ygoy.com/2010/05/10/negative-calorie-foods-chart and www.fatfreekitchen.com/negative-calorie-foods.html
calorie
Fat foods
There is no such thing as negative calorie foods. Sorry to break it to you.