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The ornish diet is recommended by many doctors and nutritionists, especially to patients needing to lose weight or prevent cardiovascular issues (it was even once endorsed by Bill Clinton!).

It is also ranked within the top 10 overall best diets in the “U.S. News & World Report’s best diet rankings”.

The diet was created by Dean Ornish, a medical doctor and professor at the University of California, who founded the Preventive Medicine Research Institute around 25 years ago.

Similar to a few other diets, the general concept is a low fat diet that aims to prevent the progression of cardiovascular disease and even reverse the build-up of plaques on arterial walls.

What Is The Ornish Diet?

The ornish diet is a modified form of the vegetarian diet, as it essentially removes the consumption of meat, fish, and eggs. Small amounts of dairy can be included in moderation.

The Ornish Diet emphasizes whole grains, fruits, vegetables, and limits refined carbohydrates, animal proteins, and fat. The diet is best known for its claims of preventing and reversing heart disease.

To main principles of the ornish diet are:

  • No more than 10% of total calories should come from dietary fat.
  • Focus on beans, legumes, fruits, grains, and vegetables to keep satiated.
  • Consume low- or non-fat dairy products in moderation (1 serving per day max).
  • Avoid meat, oils, and other high-fat foods such as avocados, olives, nuts, seeds, full-fat dairy.
  • Eat small and frequent meals to combat hunger.
  • Exercise for 30 minutes a day, 5 days a week, or 60 minutes a day, 3 days a week.
  • Quit toxic habits such as smoking and drinking alcohol.

The Health Benefits Of The Ornish Diet

Focus On Whole Plant Foods

In America, it is estimated that ~40% of the population is obese, equating to ~90 million adults [1].

To combat this, low-fat plant-based diets are known to be a beneficial tool for weight loss, mainly due to the high fiber content and the exclusion of processed foods [2].

A study found that overweight adults were able to lose ~10lbs on a whole foods plant-based diet and sustain this weight loss for at least a year after the study had finished [3].

However, there is far more to a plant-based diet than merely weight loss. It can also be very effective for preventing the onset of many diseases such as certain cancers [4], neurodegenerative diseases [5], and diabetes [6].

The weight loss that typically occurs on a plant-based diet is definitely partly responsible for the subsequent health benefits, but the high intake of certain micronutrients and antioxidants plays a key role [7].

Antioxidants are molecules that fight damage by free radicals by giving them an electron to neutralize their activity. A well-structured plant-based diet usually would have high intakes of many antioxidant vitamins such as Vitamin C, vitamin E, and flavonoids.

May Improve Cardiovascular Health

Although a lot of evidence exists that supports the use of a conventional plant-based diet for preventing cardiovascular disease, the ornish diet has actually been directly used in a clinical trial. This was called the Lifestyle Heart Trial, conducted by Dean Ornish and others at the California Pacific Medical Center.

In this study, 48 patients who had been diagnosed with cardiovascular disease were split into 2 groups; one to a lifestyle plan that included the fat-restricted ornish diet, and the other being a control group that did not receive any lifestyle interventions. Over a period of 5 years, people on the ornish diet had significantly less cardiovascular events than individuals in the control group. Further, the ornish diet group had a 3% regression in the size of their coronary artery plaques [8].

Observational studies also find similar diets, such as the vegan diet, have up to a ~75% and ~40% lower relative risk of developing high blood pressure and dying from heart disease, respectively [9].

This is mainly due to such a diets ability to improve glycemic control and lower LDL “bad” cholesterol levels [10]. LDL cholesterol are extremely prone to damage by free radicals and are closely linked to the development of atherosclerosis [11].

The Potential Negatives Of The Ornish Diet

May Lead To Nutrient Deficiencies

The Academy of Nutrition and Dietetics state that plant-based diets can be considered appropriate for all stages of life [12].

However, many reports suggest that there is potential for plant-based diets to lead to insufficient intake of certain nutrients such as omega-3 fatty acids, iron, zinc, calcium, and vitamins D and B12 [13].

The reason for this is due to a lack of these vitamins within plant foods (mainly found in animal foods), in addition to the inferior bioavailability of these nutrients in plant form (due to presence of antinutrients).

The most well-known antinutrients are oxalate, phytate, lectins, tannins, and protease inhibitors, which combine to reduce the absorption of iron, zinc, magnesium, calcium, and protein.

It is advised that people transitioning to the ornish diet get their blood nutrient levels measured, and take supplements accordingly to minimize the risks of deficiency in these nutrients.

Low Fat Diets May Cause Issues

The ornish diet can be defined as being very low fat, as it provides less than 15% of total calories from fat.

This has the potential to be problematic for certain individuals, as fat serves very important physiological purposes such as building cell membranes, synthesizing hormones, and aiding the absorption of fat-soluble vitamins; A, D, E, and K.

Despite low fat diets being originally promoted due to the health implications that were associated with saturated fat, more recent data has revealed saturated fat does not cause heart disease [13].

Other studies also support the position that significantly lowering fat intake does not improve heart health, outside of the benefits from caloric restriction [14].

This is not to say that dietary fat does not come with some health concerns, but it should be part of a balanced diet and severely restricting its consumption to very low amounts is not recommended.


The ornish diet is a low fat plant-based diet that is utilized by many doctors and nutritionists to treat their patients.

Especially for someone previously on a standard western diet, transitioning to the ornish diet will lower their risk for cardiovascular disease, diabetes, neurological disorders, and certain cancers.

However, the removal of animal products leaves a person susceptible to deficiencies if the diet is not well-planned and balanced, especially regarding omega-3 fatty acids, iron, zinc, calcium, vitamin D, and vitamin B12.

Dramatically lowering fat intake is also not necessary for optimal health, and could lead to hormonal issues and a reduced absorption of fat-soluble vitamins.

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This article has been reviewed and fact-checked by a certified nutritionist, and only uses information from credible academic sources.