The food combining diet is based on the work of Dr William Hay who spent many years developing its principles. Our diet plan review explains the thinking behind his theory. The food combining diet essentially involves not eating different nutritional groups such as proteins, carbohydrates or starches at the same time. Experiments have shown that starches are dissolved in two hours, proteins are dissolved in four hours, but protein-starch combination recipes can take up to thirteen hours to be fully absorbed into the body.

Followers of the food combining diet believe it's not important what we eat but what we are able to digest, and it's this important distinction that makes the diet meal plans of the Food Combining Diet healthy and effective. Digestive enzymes are secreted in very specific amounts and at very specific times. Different nutritional groups require different digestive enzymes. The food combining diet recognises this and plans its recipes around the fact that carbohydrate requires carbohydrate splitting enzymes whilst protein requires protein splitting enzymes. For example it recommends not eating a concentrated protein dish with a concentrated carbohydrate dish, as the digestive system has to work against itself in order to digest the carbohydrates and the proteins.

Utilising this knowledge, Dr Hay's original programme has gone on to form the basis of many other programmes. Its followers claim tremendous health benefits, such as improved energy levels, freedom from gastro-intestinal problems as well as weight loss. Critics of the programme say the science behind it is dubious, and it places tremendous restrictions on what and where you can eat.