What Is the Ornish Diet?

Ornish diet

Verywell / Debbie Burkhoff

The Ornish diet is designed to be a heart-healthy eating plan. It not only restricts dietary fat quite severely (to less than 10% of daily calories) but also requires that any ingested fats come from purely plant sources. In both the medical literature and in the popular press, the Ornish diet has been lauded as effective in preventing the progression of coronary artery disease (CAD) and even in facilitating an actual improvement in coronary artery plaques.

However, the idea that low-fat diets, such as those recommended for so many years by the U.S. government and the American Heart Association (AHA), are effective at preventing atherosclerotic cardiovascular disease has now been generally discredited. Over the past several decades, clinical studies in which dietary fat was restricted to less than 25% of daily calories have failed to demonstrate a cardiovascular benefit. Eventually, the AHA quietly dropped its low-fat diet recommendation.

The question is: Despite the fact that the AHA-style fat-restricted diet has failed to prevent atherosclerosis, does the ultra-restrictive Ornish-type diet work in other ways?

What Experts Say

"The Ornish diet is a very low-fat meal plan designed to promote cardiovascular health. Though there has been some controversy, this diet has proved successful for heart health in several scientific studies. Experts acknowledge it may be difficult for people to adhere to, though."
Chrissy Carroll, RD, MPH


All of the books, websites, TV appearances, speeches, editorials, and documentaries that tout the effectiveness of the Ornish diet can be traced back to a single clinical trial—the Lifestyle Heart Trial, conducted in the 1980s and 1990s by Dean Ornish, MD, and his group at the California Pacific Medical Center in San Francisco.

They enrolled 48 patients (45 of whom were men) who had known CAD. Twenty-eight were randomized to a special program of comprehensive lifestyle changes which included the severely fat-restricted, vegetarian Ornish diet, along with smoking cessation, meditation and stress management, and a formal exercise program. The other 20 patients, the control group, did not receive this intensive lifestyle management program. During a 5-year follow-up period, patients in the study group experienced significantly fewer cardiac events than those in the control group, and also had a 3% regression in the size of their coronary artery plaques (as compared to an increase in plaques in the control group).

The Ornish empire is built on this one small study. There was a substantial drop-out of patients during this study, and these patients were subsequently excluded from analysis. Drop-outs are especially important in small studies since the loss of data can significantly impact the results. The small size of the study also produced substantial baseline differences between the two groups. For instance, the control group had higher total cholesterol and LDL cholesterol values and were older and thinner than the treatment group. Again, these sorts of problems are common to small clinical trials, and they create inherent difficulties in interpreting differences in outcomes between the groups.

Finally, even if the reported results of the Ornish study did turn out to be accurate, it is impossible to attribute any of this benefit specifically to the Ornish diet. This is because the other three interventions applied to the study group (smoking cessation, stress management, and regular exercise) are all known to improve cardiac outcomes in patients with CAD.

There is little doubt that an aggressive lifestyle management program is a useful thing in patients with CAD. But especially in view of the general failure of low-fat diets to improve cardiac outcomes in other studies, substantial doubt exists as to how much benefit the dietary component of this study contributed to the favorable outcomes.

How It Works

The Ornish diet is a very low-fat vegetarian eating plan. Actually, it is a spectrum: On the more extreme end is the "reversal" program, used with the goal of reversing heart disease. A less-restrictive version is the "prevention" program. The Ornish diet also encompasses lifestyle changes including exercise, stress management (through breathing, meditation, and/or yoga), relationships (spending time with, and getting support from, loved ones), and smoking cessation, if you are a smoker.

What to Eat

Compliant Foods
  • Fruits

  • Vegetables

  • Whole grains

  • Legumes, seeds, and nuts

Non-Compliant Foods
  • Meat, poultry, and fish

  • Egg yolks

  • Refined carbohydrates

  • Saturated fats

  • Dairy products (in excess)

  • Alcohol and caffeine (in excess)

Fruits and Vegetables

This diet is vegetarian, so prepare for plenty of produce. In addition to those fruits and veggies, you will use vegetarian sources of fats, such as olive oil, for cooking.

Whole Grains

On this diet, you must swap refined carbohydrates for whole grain versions—so, whole-wheat bread instead of white, for example.

Legumes, Seeds, and Nuts

Legumes are a good source of protein in a plant-based diet. More nuts and seeds are available on the prevention plan.

Meat, Poultry, and Fish

On the reversal Ornish diet, no animal proteins are allowed, since they contain saturated fats. On the prevention plan, some fish is included since it is a good source of omega-3 fatty acids.


Egg whites are permitted, but not yolks, because of their cholesterol content.

Dairy Products

Small amounts of nonfat milk or yogurt are allowed.

Alcohol and Caffeine

Both are permitted, but only in very small amounts (no more than 2 ounces of alcohol per day; green tea only).

Recommended Products

Dr. Ornish has written several how-to books to fully describe his recommendations, and cookbooks to help those on his diet learn a new way to cook.


As described above, the Ornish diet is not a singular plan, but a spectrum of offerings that range from very low-fat and completely vegetarian to more flexible options that incorporate fish, chicken, avocados, nuts, and seeds.

Pros and Cons

  • No associated health risks

  • Satisfies hunger

  • Accessible

  • Restrictive

  • Hard to sustain

  • Time-consuming



There are no special health risks associated with the Ornish diet, as long as basic nutritional needs (for protein, carbohydrates, and nutrients) are met. However, its health claims may not be completely supported by scientific evidence.


Although the Ornish diet limits the types of foods that are consumed, it does not limit the amounts. Eating plenty of fruits, vegetables and whole grains can usually satisfy hunger.


No specialty foods are required on this diet, and the complaint foods are readily available. Sometimes they can be more expensive (e.g., quinoa pasta vs. traditional versions), but you also save money by cutting out meat. In addition, there is no calorie-counting or food-tracking, which may be appealing to some users.

While there are many positive aspects of this diet, it is not a cure-all and it is not perfect for everyone.



Eating a low-fat, vegetarian diet still allows for balanced nutritional intake, as long as special attention is paid to iron and omega-3 fatty acids. However, cutting fat down to 10% of daily intake is challenging for most people. Due to protein limitations, this may lead to a higher carbohydrate intake which may not be beneficial for someone who has pre-diabetes or diabetes.


For that reason (the restriction on fats, not to mention refined carbs, alcohol, and caffeine), some people may find it difficult to follow this diet for the long term. It is meant to be a lifelong change, not a temporary one.

Time commitment

Eating vegetarian can take a lot of prep and cooking time. You also may need to learn how to cook differently, without meat and saturated fats. Also, most convenience foods and meals are off-limits on this diet.

How It Compares

The Ornish diet shares many characteristics with other low- or no-meat and "heart-healthy" diets. It also generally meets USDA recommendations on nutritional balance, with some planning and effort.

The 2020 U.S. News and World Report Best Diets ranks the Ornish diet number 9 in Best Diets Overall and gives it an overall score of 3.6/5.

USDA Recommendations

Although the USDA MyPlate guidelines include meat, the Ornish diet can meet these recommendations based on its emphasis on fruits, vegetables, and whole grains.


The USDA suggests roughly 2000 calories per day for weight maintenance, although this number can vary significantly based on age, sex, current weight, and activity level. The Ornish diet is based on reducing fat, not calories, so calorie intake will be different for everyone following the diet.

Similar Diets

This is how the Ornish diet compares to other low- or no-animal fat diets.

Ornish Diet

  • Accessibility: No special foods, supplements, food tracking, or calorie counting are required.
  • Effectiveness: Some studies have shown the Ornish diet can be effective in measures of heart health and weight loss.
  • Sustainability: It may take some time to adjust to this style of eating, especially the "reversal" program. The prevention program is likely to be easier to follow and to stick with long term.

Vegetarian Diet

  • Accessibility: Again, on a vegetarian diet, no special foods are required (unless you want meatless versions of foods like hot dogs or chicken tenders) and there's no tracking your food. Just avoid meats.
  • Effectiveness: If you are going vegetarian to lose weight, you will still need to be aware of your calorie intake.
  • Sustainability: Many people adapt to and enjoy a meat-free diet for life.

Vegan Diet

  • Accessibility: People on a vegan diet do not consume any meat products at all, unlike vegetarians who do eat eggs and dairy products. It is more challenging to meet nutritional needs this way, and some special foods and supplements might be necessary.
  • Effectiveness: Many people lose weight on a vegan diet, and there may be other heart-health and disease-prevention benefits.
  • Sustainability: Like the Ornish diet, a vegan diet requires a significant commitment to sustain.

Mediterranean Diet

  • Accessibility: The Mediterranean diet is probably the easiest to access. It does not eliminate meat, but de-emphasizes it in favor of fish, legumes, and some dairy products. It is not a low-fat diet.
  • Effectiveness: Some studies have shown the Mediterranean diet to be more effective than lower-fat diets in weight loss and other health measures. The 2020 U.S. News and World Report list of best diets ranks the Mediterranean diet as the #1 overall diet.
  • Sustainability: The Mediterranean diet is meant to be a long-term lifestyle change, and that change is manageable for most people.

A Word From Verywell

Based on the results of the Ornish study—the small randomized trial upon which all the famous claims regarding the Ornish diet are based—the notion that an ultra-low fat vegetarian diet improves CAD should be regarded as an intriguing hypothesis. Still, for weight loss, this diet holds promise and experts say that it is generally safe (although potentially difficult) to follow.

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