Hay diet


Food combining guidelines

Food groups


Combine with

Do not combine


Acid fruits

Grapefruit, oranges, lemons, limes, pineapples, pomegranates, tomatoes

Sub-acid fruit and nuts and seeds

Sweet fruit and other food groups

Tomatoes can be eaten with low and non-starchy vegetables and avocado

Sub-acid fruits

Apples, apricots, berries, grapes, kiwi, mango, nectarines, papaya, peaches, pears, plums, strawberries

Acid or sweet fruits, not both, and nuts and seeds

Other food groups

Sweet fruits

Bananas, coconut, dates, dried fruits, prunes, raisins

Sub-acid fruits, and nuts and seeds

Acid fruit and other food groups


Cantaloupe, honeydew, watermelon

Eat alone

All groups


Meat, poultry, fish, eggs, dairy, dry beans/peas, nuts & seeds, peanuts, soy beans, soy products, tofu

Low and non-starchy vegetables

Other proteins, fats, carbohydrates and starches, and fruits

Drink milk alone

Low and non-starchy vegetables

Asparagus, artichokes, green beans, beets, broccoli, cabbage, cauliflower, cucumber, eggplant, garlic, lettuce, celery, carrots, onions, parsley, peas, peppers, turnips, mushrooms, zucchini

Protein, fats, carbohydrates, and starches


Carbohydrates and starches

Bread, pasta, grains/cereals, potatoes, pumpkin, winter squashes, yams

Low and non-starchy vegetables and fats

Fruits and protein


Avocado, olives, coconut, butter, cream, and olive, avocado, flax, sesame, and canola oils

Low and non-starchy vegetables, carbohydrates and starches, and protein

Protein, fruits

Avocado can be eaten with fruits


When William Howard Hay (1866–1940) graduated from New York University Medical College in 1891, he practiced medicine and specialized in surgery. That changed 16 years later when his own medical troubles led him to research the connection between diet and health. Hay then weighed 225 pounds (102 kg) and had high blood pressure and Bright's Disease, a kidney condition. Hay discovered that his heart was dilated while running to catch a train.

The dilated heart caused by weakened heart muscles meant that his blood could not pump efficiently. Hay knew from treating patients that his future did not “look overlong or very bright,” according to his 1929 book Health via Food. The title described Hay's health theories, his condition, and treatment.

Hay diagnosed the causes of his conditions as the “very familiar trinity of troubles” that then ranked as the primary cause of death: the combination of high blood pressure, kidney disease, and a dilated heart.

Hay wrote that his legs had swelled, and he slept seated because he was afraid he would drown in his fluids if he slept lying down. He wasn't able to lose the weight through exercise and what he thought was a proper diet. Hay wrote that the dilated heart made his prospects bleak. He knew from treating patients that there was no medical treatment for a dilated heart. He advised them to prepare for the “final hopoff” (death). With that diagnosis applied to himself, Hay looked at his life to evaluate his own situation. He described himself as a “strong man of splendid heredity,” so Hay looked at his eating habits.

Plain food of the American table

After graduating from medical school, Hay ate at hotels, boarding houses, and restaurants for 11 years. He then married, and his wife prepared meals for the following five years. As a married man, Hay wrote that he could control what he ate. However, his food preferences were formed during his years of “public eating.”

At home, each of Hay's meals consisted of meat or other concentrated protein. He usually combined this with white bread and generally ate a potato of some form. Hay described this meal as the “plain food of the American table.” His meal ended with pastries and two to three cups of coffee that he sweetened with sugar and cream.

Hay's eating habits weren't unusual. Meat and potatoes were long part of a traditional American meal. In addition, Americans during the early 1800s tended to eat large meals. Excess weight was regarded as a sign of prosperity. That perspective began to change later in the century, with a range of weight-loss solutions proposed during the 1890s.

Dr. Edward Hooker Dewey's plan involved skipping breakfast. Horace Fletcher, a businessman, created a plan after he couldn't get life insurance because of his weight. He lost 40 pounds (18.1 kg) by slowly chewing his food until it liquefied. He then swallowed it. The slow-chewing technique became known as “Fletcherism.”

Developing a new diet

Hay started his special diet by eliminating two meals and eating only vegetables for the third. He stopped drinking coffee, but continued to smoke cigarettes and drink alcohol. Hay wrote that his craving for coffee ended in two weeks. Several months later, he gave up smoking. By the third month, Hay weighed 175 pounds (79.4 kg).

Hay considered that a normal weight. He spent the next four years researching diet and exercise, examining those issues from the conventional and alternative perspectives. His research included studying the work of Ivan Petrovich Pavlov, the Russian physiologist known for his research involving dogs. Pavlov's studies of the digestion process of dogs indicated that it took about two hours to digest starches and four hours to digest proteins. However, it could take thirteen hours to digest a mixture of protein and starch.

Hay's research led to a diet based on the theory that health was affected by the chemical process of digestion. The body uses an alkaline digestive process for carbohydrates, the group that Hay classified as consisting of starchy foods and sweet things. The digestion of proteins involved acid. If carbohydrates and proteins were consumed at the same time, the alkaline process was interrupted by the acid process. Combining incompatible foods caused acidosis, the accumulation of excess acid in body fluids. Hay linked the combination of foods to medical conditions like Bright's disease and diabetes. The wrong combinations “drained vitality” and caused people to gain weight.

Hay maintained that the solution was to eat proteins at one meal and carbohydrates at another. He classified fruits with acids. Hay labeled vegetables in the neutral category that could be consumed with either group. He also advocated the daily administration of an enema to cleanse the colon.

The Hay diet was credited with curing the doctor. He pointed out in Health via Food that the book was written 24 years after his bleak diagnosis. Hay said that after changing his eating habits his blood pressure was lower, the swelling caused by fluid was gone, and he could run quickly and at a distance.

He gave up his traditional medical practice, surgery, and administering drugs. He believed that his eating plan was more beneficial. Hay introduced his diet in 1911 and spent the rest of his life promoting it. He lectured in the United States and Canada and wrote books. The Medical Millennium was published in 1927, followed by Health via Food in 1929 and A New Health Era in 1939.

In addition to writing diet books, Hay used the diet to treat patients at sanatoriums. He worked as the medical director of the East Aurora Sun Diet and Health Sanatorium in New York state from 1927 through 1932. He then founded the Pocono Haven Sanatorium Hotel in Mount Pocono, Pennsylvania. He served as its director until he died in a traffic accident in 1940.

Hay's eating plan was the forerunner of late twentieth century food combining diets, including Stephen's Twiggs' Kensington diet and Judy Mazel's New Beverly Hills diet.


William Howard Hay evaluated health theories and weight loss methods while developing his plan. When he concluded that proper food combination was the solution to improved health, he saw some benefits in Fletcherism. The slow-chewing method could aid in the digestion of incompatible foods in some cases, Hay wrote in Health via Food. Bread could be chewed into a liquid, but the process wasn't effective with foods like cheese.

Hay also maintained that fresh air provided a benefit, especially when people slept. However, the Hay diet was the foundation of his treatment. The plan, which scheduled when food was consumed, generally consisted of one food group per meal. Foods were classified as proteins, starches, and neutral foods that could be combined with proteins or starches. Health via Food included a month-long schedule of suitable meals. It gave the public a guide to follow. For the contemporary reader, the diet plan offers a perspective on the Hay diet and the eating habits of those times. Although food items were limited, people could eat as much as they wanted.

The Hay diet menus for the summer included the following meal recommendations:

The contemporary Hay diet

Contemporary versions of the Hay diet no longer recommend a daily enema. The eating plan still follows Hay's classification of foods into three categories, along with the rules about how the foods are combined at mealtime. The diet consists primarily of fruits and vegetables, and dieters are advised to wait at least four hours before consuming a meal from an incompatible category.

Some versions of the Hay diet recommend eating small portions of proteins, starches, and fats. There is also an emphasis on eating whole-grain products and unprocessed starches. Some plans allow alcoholic beverages; others prohibit processed foods with ingredients such as refined sugar, margarine, and white flour.

Body mass index (BMI)—
Rates a person's weight as healthy, underweight, overweight, or obese. The BMI can be calculated by converting the person's height into inches. That amount is multiplied by itself and then divided by the person's weight. That number is then multiplied by 703. The metric formula for the BMI is the weight in kilograms divided by the square of the height in meters.
The nutritional term for a kilocalorie, the unit of energy needed to raise the temperature of one liter of water by one degree centigrade at sea level. A nutritional calorie equals 1,000 calories.
A nutrient that the body uses as an energy source. A carbohydrate provides 4 calories of energy per gram.
Insertion of a tube into the rectum to infuse fluid into the bowel and encourage a bowel movement.
A nutrient that the body uses as an energy source. Fats produce 9 calories per gram.
A complex carbohydrate not digested by the human body. Plants are the source of fiber.
Morbidly obese—
Also known as extremely obese, the condition of someone with a BMI of more than 40.
Having a BMI of 30 or higher.
Having a BMI of 25 to 30.
A nutrient that helps build many parts of the body, including muscle and bone. Proteins produce 4 calories per gram.

The Hay diet meal plan is based on the categories of proteins, starches, and neutral foods. Proteins and neutral foods may be combined, and neutral foods may be combined with starches. The combination of proteins and starches should be avoided.

The protein category consists of:

In the neutral foods category are:

In the starches category are:


Hay created his meal plan to treat medical problems associated with obesity. He claimed that a change in eating habits rather than medication was beneficial in the treatment of conditions such as cardiac disease, kidney disease, and kidney disorders.

In contemporary times, the Hay diet is used as a weight loss plan by the general public and people interested in alternative treatments. Advocates of natural health maintain that the plan reverses conditions such as arthritis, indigestion, constipation, and flatulence. The Hay diet is also regarded as a natural method for providing relief to people diagnosed with asthma and allergies.


Hay wrote in Health via Food that he saw “the comeback of thousands of patients” who followed his regimen. The Hay diet features some nutritional principles endorsed by organizations including the U.S. Department of Agriculture (USDA), the Academy of Nutrition and Dietetics, and the medical community. Their recommendations call for eating lean meat and poultry and a variety of fruits and vegetables.


Those recommendations are also found in the Hay diet. People who follow those recommendations and fill up on fruits and vegetables will lose weight. Those are low-calorie foods that are rich in fiber. Whole grain products also contain fiber. Eating high-fiber food produces the sense of fullness more quickly than the consumption of foods with fat does.


Although there are some nutritional aspects of the Hay diet, there are some flaws. The diet does not include serving sizes, and portion control is an important aspect of maintaining a healthy weight. In addition, people may miss out on vitamins and nutrients by restricting food groups to one meal per day.


Although the consumption of fruits and vegetables will help to relieve constipation, people should not rely solely on the Hay diet to treat conditions such as heart disease, arthritis, allergies, and asthma. People diagnosed with those conditions may need medication and should consult their physician before undertaking the Hay diet or any weight loss plan.

Research and general acceptance

Food combining diets are generally not supported by the medical community and are not supported by clinical evidence.

See also Beverly Hills diet ; Body mass index ; Obesity .



Hay, William Howard. Health via Food. 1929. http://www.soilandhealth.org/02/0201hyglibcat/020165.hay.pdf (accessed April 5, 2018).


Clarke, Jane. “Sorry, but Food Combining is Just a Silly Fad!” DailyMail.com , January 29, 2008. http://www.dailymail.co.uk/debate/columnists/article-509672/Sorry-food-combining-just-silly-fad.html (accessed April 5, 2018).

Liz Swain

  This information is not a tool for self-diagnosis or a substitute for professional care.