In 1911, Dr. William Howard Hay made known about food combining. After practicing medicine for 16 long years, Dr. Hay developed some forms of illnesses like high-blood pressure, dilated heart, and Brights disease or more popular as chronic nephritis, which is a kidney-related disease.

Since around that time, there was no available treatment yet for enlarged heart conditions, this provoked Dr. Ray to come up with treatments to his deteriorating health. His basic instinct told him than in every health condition, there must be an underlying cause to trigger such health problem. Then, he came up with improper chemical components within the body as the basic cause.

He experimented on himself. He did it by "eating fundamentally" as he would put it. He took foods in its most natural form, with no protein and starch combination together in the same banquet. The incorrect chemical condition was acidity, which was acquired by too much ingestion of highly acidic foods. These acids collected were in higher levels that the body cannot tolerate anymore.

Along with his form of diet, Dr. Hay recommended physical activities like exercises, fresh air and lifestyle changes. Actually, Dr. Hay’s number one rule for the diet is not combining starch and sugar with acid fruits and protein in the same meal. Second, salads, fruits and vegetables should be given importance within the course of the diet, and protein, fats and starch must be taken in moderation or very less amounts. Wholegrain and unprocessed starches are the only ones recommendable. It is also advisable to give at least four hours interval for the next meal of another food group, Dr. Hay calls this a "food combining" diet. Acidic foods include those that are rich in protein, dairy, meat, and fish, while carbohydrate-rich foods include, grains, potatoes and rice.

Strict compliance to this Hay Diet reverses degenerative and chronic conditions like arthritis, indigestion and constipation. This is favorable for those with allergy and asthma. Another benefit is the weight loss effect reducing the risks of obesity-related maladies such as gallstones, heart diseases, and diabetes.

As Dr. Hay attempted to treat his own systems, his doctors were surprised and he was relieve to find out that after three months of his own remedy, his condition does improved. Because of this, he came to believe that somehow, medicine has some glitch to treatments of diseases. He thought it should work if medicine could come near to treating the illness itself rather than the aftermath of the predicament.

Dr. Hay was convinced then that he had a successful approach to treating diabetes. He started treating his patients with diet and showed to them how his patients can attain optimum health through diet with no irreversible organic changes. Through the years, Dr. Hays was popular for his creative method called the "Hay Diet." Aside from the diet, Dr. Hay also taught the significant importance of exercise, fresh air, daily bath and sunshine.

Despite Dr. Hay’s success in his time, he was continually criticized by medical community, who were at that time were so focused on the increasing drug usage for treatments, and germ theory of diseases. Dr. William Hay continued his practices, treating patients and doing lecture until he finally bid goodbye for good in 1940.