Recently while on a support board, I came across a concept known as "food combining". Using food combining, you are not supposed to eat carbohydrates and proteins at the same time. The foundational basis is that the enzymes used for the digestion of each macronutrient requires the opposite pH to function; carb enzymes require an alkaline solution, proteins an acidic solution. Therefore by eating both at the same time, you cancel out the digestion effectiveness of both, reducing absorption of nutrients. Versions of these theories first floated around in the 19th century, around the time the macronutrient concept was coming into being. In 1911, William Hay first introduced the idea of food combing to the United States. Later on, Dr. Herbert Shelton expanded upon the food combining concept. Using his work as a basis, several authors wrote weight loss and health books advocating food combining, including actress Susanne Somers. The most famous book about food combining was "Fit For Life", written by Harvey Diamond and selling millions of copies. Dr. Diamond claims in his book that failure to follow food combining is the reason we become fat (hmmm, it couldn't be that I sat on my butt all day stuffing my face with junk, could it?). Because we consume carbs and proteins at the same time, digestion is stopped, food is trapped in our digestive tract, begins to rots. This creates toxins, and these toxins accumulate and cause the body to store fat. By applying the methods in "Fit For Life", you will free the body of these toxins and allow nutrients to be absorbed. Your body will be able to burn off all its fat and all of your health problems will be cured as well (I wonder if we would get three wishes too).
The problem with food combining is the basic premise has no scientific basis. Humans, as omnivores, are able to eat carbohydrates and proteins simultaneously. Not one study has shown our bodies unable to digest either proteins or carbs at the same time. Many studies do, however, show that mixed meals actually improves our digestion process. Furthermore, our small intestine tract is always acidic, regardless of what we have eaten. The statements and claims made by in "Fit For Life" are even more erroneous. First, the food we eat does not rot in the stomach; it is either broken down by digestion and absorbed, or, it is passed through and excreted, period. Secondly, toxins do not cause the body to store fat. Body fat is built up from triglycerides that are converted from food that itself has been broken by the digestive process. The weight loss that adherents experienced from following "Fit For Life" can be accounted for by other explanations; the limited food choices or the low caloric intake. Additionally, "Fit For Life" states you should not consume proteins in the morning. This is not a healthy practice; our bodies need an influx of proteins. If we do not get them from our diet, it will take them from our muscles. Upon waking, you most likely went hours without any proteins at all, even if you took some prior to sleeping. To go additional hours without eating any protein at all risks serious leaching of muscles.
During my weight loss, and the maintenance period following I consistently consumed carbs and protein together. Of course my experience is not enough proof. I did find two class of people who also consume both on a regular basis. Bodybuilders are among the leanest people in the world, many of them having low single-digit body fat compositions especially during competition season. Virtually all of them eat lots and lots of chicken breasts and rice together. If food combining was valid, they should not only be packing on fat, they should also experience a myriad of health problems. The Japanese consume sushi, consisting of rice and raw fish, in huge quantities. According to food combining, they should have a high rate of obesity. Instead, they have the lowest rate, and the highest life expectancy as well.
In conclusion, food combining is another fad diet. Overall, the diet not harmful, simply ineffective, and due to the low protein content of the meals, one that is actually counterproductive for those building or maintaining muscles. The most effective method to lose weight still consists of healthy eating combined with physical activity.