What Is the Ornish Diet? How Is It Followed and What Are Its Benefits?

First designed in 1977, the Ornish diet is a low-fat, plant-based eating pattern. It encourages many healthy foods while prohibiting others. 

US News & World Report, which has classified diets by their characteristics and abilities for 10 years, placed the Ornish diet in its “Best Diets 2021” list, giving it an average score of 3.6 out of 5 and placing it in 9th position. The scores across the parameters were: 

What Does the Ornish Diet Include?

Researcher and founder of the Preventive Medicine Research Institute in California, Dr. Ornish, designed the Ornish diet as a lacto-ovo-vegetarian eating pattern. It prohibits meat, fish and poultry while allowing limited amounts of milk / dairy products and eggs. “Lacto” refers to dairy products and “ovo” to eggs.

As a lacto-ovo-vegetarian eating pattern, the Ornish diet generally encourages plant-based foods. In addition to vegetables and fruit, it allows legumes, soy products and whole grains. Another characteristic is its low fat content. Foods consumed are recommended to be low in fat.

Let us examine in detail which foods are allowed, limited or prohibited:

Allowed Foods

• Fruit:  apples, bananas, oranges, kiwifruit, grapefruit, strawberries, pomegranates, melons, pears, apricots
• Vegetables: broccoli, cauliflower, cabbage, cabbage, peppers, garlic, onions, spinach, zucchini
• Legumes: beans, chickpeas, red lentils, green lentils

Foods Recommended in Limited / Small Amounts

• Nuts and seeds (3 or fewer small portions daily): for example, walnuts, almonds, cashews, walnuts, pumpkin seeds, chia seeds, flaxseeds
• Low-fat packaged foods: for example, whole-grain cereals, whole-grain crackers, frozen vegetarian burgers
• Caffeinated drinks: one cup of coffee or two cups of black tea/decaffeinated coffee daily
• Dairy products (2 or fewer portions daily): for example, fat-free yogurt, skimmed milk, low-fat cheese
• Fats: for example, olive oil, avocado, coconut oil, vegetable oil, canola oil, olives
• Refined carbohydrates (2 or fewer portions daily): for example, white pasta, crackers, biscuits, white bread, pancakes, white rice, honey, brown sugar, white sugar
• Alcohol (no more than 1 serving daily): for example, wine, beer, liqueur
• Processed foods: for example, high-fat ready meals, baked goods, fast food, potato chips, simit

Prohibited Foods

• Meat: for example, beef, lamb, goat, veal
• Seafood: for example, salmon, mackerel, tuna, anchovies, sardines, shrimp, lobster
• Poultry: for example, chicken, turkey, goose, duck
• Egg yolk

What Should Be Considered When Following the Ornish Diet?

• As noted above, healthy fats such as walnuts, almonds, hazelnuts and avocado are allowed, but in limited quantities. For example, 3 exchanges of raw almonds correspond to 15 almonds.
• Vegetables, fruit, soy products and whole grains should make up most of the plate. Daily fat consumption is recommended not to exceed 10% of total daily energy intake.
• Milk and dairy products are allowed, but only fat-free / low-fat options, not exceeding 2 portions daily.
• Animal foods such as meat and chicken are completely prohibited, lowering saturated fat intake. To restrict saturated fat substantially, however, not only meat products but also fats rich in saturated fat, such as butter, must be excluded.
• Eggs are allowed, but because the diet restricts saturated fat, egg whites rather than yolks are recommended.
• Caffeinated drinks, refined carbohydrates, sugar, alcohol and low-fat packaged foods are not prohibited, but substantial restrictions on consumption are recommended.

What Are the Health Effects of the Ornish Diet?

The table at the beginning shows the diet's scores on different parameters. Let us examine its health effects, particularly given its high score for heart health.

The Ornish Diet and Obesity

The Ornish diet mainly contains nutrient-rich but low-calorie foods such as vegetables and fruit. There are 4 calories in 1 gram of carbohydrate, 4 in 1 gram of protein and 9 in 1 gram of fat. Its fat restriction may therefore substantially reduce daily calorie intake. Refined carbohydrates and packaged foods such as pastries, wafers and ready-made fruit juice are also major causes of obesity. Restricting these foods supports obesity treatment. Consider a study investigating the rate of weight loss with fat-restricted versus carbohydrate-restricted diets in people with obesity:

2015 was the year when Cell Metabolism published a study in which 19 participants ate a carbohydrate- or fat-restricted diet for 6 days. Participants eating the carbohydrate-restricted diet lost 53 ± 6 g daily, whereas those eating the fat-restricted diet lost 89 ± 6 g. The study suggests fat-restricted diets may be more suitable for achieving weight loss in people with obesity (1).

However, although foods such as vegetables and fruit have fewer calories than high-fat packaged foods or red meat, they still contain calories. People wanting to lose weight should therefore not consume excessive fruit.

2005 was the year when Clinical Trial published another study investigating weight loss with popular diets including Ornish, Zone (a pattern with 40% of energy from carbohydrate, 30% from protein and 30% from fat, aiming to reduce inflammation), and Weight Watchers. Participants were randomly assigned to different diet groups. The study lasted 1 year and included 160 participants. Ornish was observed to be the group losing the most weight, with participants following that diet losing an average of 3.3 kg (2).

• Related topic: What Is the Weight Watchers Diet and How Is It Followed?

The Ornish Diet and Heart Health

The Ornish diet, in US News & World Report's “Best Diets 2021” list, was selected as one of the best diets for heart health. Encouraging heart-friendly foods and prohibiting high-fat foods such as red meat were key factors. High-fat foods, particularly saturated fats, raise lipid profiles such as LDL cholesterol that adversely affect cardiovascular health, whereas vegetables and fruit, rich in fiber, vitamins and minerals, are heart-friendly.

2009 was the year when Journal of American Diet Association published a study of 3 different diets' effects on lipid profiles: Atkins, South Beach and Ornish. Atkins severely restricts carbohydrate and is high in protein and fat; South Beach restricts carbohydrate and recommends lean protein and healthy unsaturated fats. The study involved 24 participants with a mean age of 30, observed for 4 weeks. The greatest reductions were observed with Ornish in the following values, described as bad cholesterol: LDL cholesterol, total cholesterol and CRP (a blood test measuring inflammation). However, among Ornish participants, the value known as good cholesterol, HDL levels decreased compared with those of participants on the other diets. This is because, under Ornish, HDL cholesterol-raising healthy fat groups such as walnuts, fish and olive oil are also consumed in limited amounts (3).  

Beyond dietary advice, Ornish recommendations on stress management, physical activity and social relationships, which matter for heart health, also contribute to its selection as a heart-friendly pattern. Research argues that stress and socially inadequate lifestyles may increase cardiovascular disease risk. Many studies also support an active lifestyle's cardiovascular benefits. The American Heart Association, The American Heart Association, also recommends at least 10,000 steps daily for good heart health.

The Ornish Diet and Diabetes

Research shows that high-fiber, vegetable-rich eating patterns play an effective role in preventing and treating diabetes. Restricting refined carbohydrates and high-sugar packaged foods is another reason Ornish is suitable for people with diabetes. In US News & World Report's “Best Diets 2021” ranking of diabetes diets, it placed 7th. People with diabetes following Ornish should, however, choose fruit and vegetables that raise blood sugar slowly and meet their protein needs.

Is the Ornish Diet Expensive?

Do You Need Training or Group Membership Before Starting?

 Healthy diets can sometimes cost more than diets based on packaged, unhealthy foods. With Ornish, choosing more affordable vegetables instead of expensive ones can keep costs down. Legumes and grains are also affordable. Because relatively costly foods such as fish, meat and chicken are prohibited, it will suit most budgets.

No training or group membership is required to follow Ornish. Those interested can find detailed accounts of the diet and lifestyle recommendations online in printed and electronic book formats.

Comment / Summary

Although the Ornish diet generally includes healthy foods, it limits or completely prohibits many foods. Any diet should be implemented as a balanced eating pattern; otherwise, deficiencies in vitamins and minerals such as B12, iron and zinc can develop. It is therefore useful to recall that the Mediterranean diet was selected as the healthiest diet overall and the best diet for heart health and diabetes in US News & World Report's “Best Diets 2021” list. Following a Mediterranean pattern can improve health, help prevent disease and minimize vitamin / mineral deficiency risk.