The rationalization behind food combining is that different food groups require different digestion times. Making the proper combinations enables the body to digest and utilize the nutrients found in food to the fullest extent. The theory of food combining is extremely confusing and unless you have a thorough knowledge of the body's inner working the science behind the process can be difficult to stomach. Among the factors that must be taken into account are the pH levels and their involvement in digestion.

Proteins need a highly acidic environment for digestion. Carbohydrates and fats on the other hand require an alkaline medium. When a protein and a carb are consumed at the same time, yet necessitate different conditions, this interferes with the digestion process. Unfortunately, the clash causes indigestion, bloating, gas, poor absorption of essential nutrients and most importantly weight gain.

Here are the basic rules of the thumb for food combining.

1. Carbs and acid foods shouldn't be eaten together. Don't eat bread, rice or potatoes with lemons, limes, tomatoes, oranges or other sour fruits.
2. Don't consume concentrated proteins and concentrated carbohydrates at the same meal. Nuts, meat, eggs, cheese, or other proteins shouldn't be eaten with bread, cereals, potatoes and sweet fruits.
3. Don't eat more than one protein at a meal. Eggs and meat, cheese and eggs, eggs and milk, and cheese and nuts are all major no no's. Milk should be consumed by itself.
4. Avoid eating fats with protein. Don't use cream, butter and oil with meat, eggs, cheese or nuts.
5. Don't eat acid fruits with proteins. Swear off oranges, tomatoes and lemons with meat, eggs, cheese or nuts.
6. Starch and sugars shouldn't be eaten together. That means no jelly on your toast and no butter on your potato.
7. Eat only one starch per meal.
8. Melons should be eaten alone.

When following a food combining program, a typical day's menu will look like this. Breakfast is a fruit by itself. Lunch should consist of a vegetable salad with no tomatoes, one cooked green veggie and a starch. Dinner is a large salad, two cooked non-starch veggies and a starch.

Time consuming and difficult to follow, there is still much debate about whether food combining actually accomplishes anything including weight loss. Some opponents of the concept suggest that food combining actually is self-defeating because the suggested combinations hinder proper digestion.