| dove l'informazione diventa benessere
April 2017
Print this
You are here: / Dietetics / Articles / New diets / Dissociated diet



The ‘dissociated diet’ was invented by Dr. William Howard Hay in 1911 and is also known as the ‘Hay diet’ or ‘food combining’. Dr. Hay was born in 1866, in Hartstown, Pennsylvania and he graduated from New York University in medicine in 1891. He then began a medical career that lasted for the following 16 years however later on, he became seriously ill and was diagnosed with Bright’s disease (a disease that causes liver degeneration). Subsequently, he then decided to take better care of what he ate and, after 3 months, there were noticeable improvements, much to the amazement of the doctors that monitored his progress.

Following this, and after many experiments, in 1911 he developed his own diet based on the principle that unbalanced accumulations of digestive and metabolic products can form in the body, which the body is then not able to get rid of, causing health problems.

Hay argued that this was due to four factors:

  • an excessive consumption of meat;
  • an excessive consumption of refined carbohydrates (starchy foods);
  • no knowledge of digestive chemicals;
  • overeating.

The basic rules of the dissociated diet

The diet is based on 5 rules:

  1. Do not eat carbohydrates with protein or acidic fruit in the same meal (* see below).
  2. Fruit, vegetables and salad should be eaten as the principle part of the diet.
  3. Eat protein, starch and fats in limited quantities.
  4. Eat wholegrain foods and avoid refined and processed foods, like those made from white flour, sugar and margarine.
  5. Leave a gap of four hours between eating each meal.

The theory

This diet is based on the analysis of the mechanisms we use to digest foods:

  1. Proteins need to be digested in an acidic environment: when proteins are swallowed, the stomach produces hydrogen chloride that activates the pepsin enzyme and divides and digests them. This process takes place in an acidic environment that is slightly neutralised by the presence of starches and sugars which come from alkaline substances (this does not mean that all the proteins are completely digested, however).
  2. In order for carbohydrates to be digested, they need to be in an alkaline environment. This process starts in the mouth with the ptyalin enzyme which begins to split the starch before it gets to the intestine, where it is split again and digestion begins.

*The presence of protein and acidic fruits reduce the alkalinity, decreasing the intestinal digestion of fats.

In short, if you eat a large amount of carbohydrates and protein mixed together in the same meal, it creates an environment that is too acidic to reduce starch and too alkaline to digest the protein well.

Many weight loss diets are based on this theory and are often claimed to be ‘new’ diets.

Is this theory true?

The scientific base and thus the effectiveness of this diet are controversial. Academics from all over regularly make a stand against this type of diet but continually, all over the world, new publications and new applications revive it.

Professor Sheldon Margen (University of California) maintains that there is no scientific proof that supports this theory and that actually ‘nearly all foods are themselves combinations’. Beans, for example, contain carbohydrates (starch and sugar), protein and fibre and our digestive system is perfectly able to manage combinations of nutrients: the process starts in the mouth where chewing and saliva begin the digestion process and break down the starches into sugars. Other enzymes then come into play, almost completing the digestion of starches no matter what they are made up of.

A specific study was carried out by a group at the University of Geneva, headed by Alain Golay. For a month and a half, 57 obese people were put in to two groups and monitored; one group followed the dissociated diet and the other ate a balanced diet. Both groups had to eat a similar amount of calories and an energy intake of 45% carbohydrates and 30% fats. Even though the dissociated diet has a slightly lower content of fats, the balanced diet came out as more effective because the candidates lost an average of 7.5kg as opposed to the 6.2kg lost by those who followed the combination diet.

For researchers, this means that losing weight does not have anything to do with when and which foods are eaten and the type of nutrients in the meals. What does count is instead a low intake of calories.

Researchers also observed that the candidates of both groups showed the same level of cholesterol, triglycerides and insulin in their bodies which indicates that the benefits associated with weight loss are the same for both diets.


Despite the fascination with this diet, scientific evidence shows that a balanced diet is more suitable for both normal food regimes and weight loss diets. Furthermore, from a point of view of taste, a balanced diet is much more practical and satisfying.

To balance the right amount foods you eat. The best method is to always abide by the ‘food pyramid’:


  • News of the month
    Discover all the latest news this month on

Copyright © 1999-2017 A.E.C. srl - ABOUT US