A Review of the Ornish Diet 

What Is the Ornish Diet? | How Does the Ornish Diet Work? | Benefits of the Ornish Diet? | Can the Ornish Diet Lead to Weight Loss? | What Do the Experts Say? | Bottom Line

Be it aesthetic concerns or questions of long-term overall health, Americans seem to always be on the lookout for the next new diet plan. This is partially driven by social media and the ongoing stigma of being overweight, but it is also driven by the very real epidemic of obesity in the United States. In addition to the generally unwelcome fact of carrying extra body weight, obesity is connected to a variety of preventable health conditions like cardiovascular disease. In recent years, new diets that are specifically developed to address obesity-related health problems. One example of such a diet is known as the Ornish diet.

What Is the Ornish Diet?

The Ornish diet was originally developed based on research conducted by Dr. Dean Ornish during the 1970s-1990s. Ornish is a Clinical Professor of Medicine at the University of California, San Francisco and the president of the Preventive Medicine Research Institute, a non-profit organization that looks at how dietary and lifestyle choices affect health outcomes. Through his research and numerous books, Ornish is a vocal advocate for lifestyle-driven approaches to treat or manage chronic diseases like coronary artery disease and type 2 diabetes.

In the years since its inception, the Ornish program has evolved into the low-fat, plant-based diet that is currently ranked 10 on the U.S. News and World Report list of best diets. While the diet was mainly developed to improve overall heart health and potentially reverse heart disease, there are a number of key components that somewhat differentiate it from other diets and meal plans:

• Plant-based: The Ornish diet is based on primarily plant-based foods that include fruits, veggies, whole grains, and legumes. Even though it isn’t strictly a vegetarian diet or vegan diet, animal products like red meat and pork are meant to be avoided or consumed in limited quantities only.
• Low-fat: Another main tenet of the Ornish diet is a focus on saturated fat intake; saturated fat has long been believed to increase the risks of heart disease as well as lead to overweight and obesity. The Ornish diet calls for only 10% of daily calories coming from fat, and even then the calories should be from healthy fats like olive oil. This focus on fat is also why the diet recommends only low-fat or nonfat dairy products like eggs (or just egg whites) or skim milk.
• Moderate exercise: Getting regular physical activity is another crucial component of the Ornish diet. There are no specific workouts associated with the diet, and participants can pick almost anything that can be considered moderate exercise, including aerobics, strength training, or yoga.
• Stress management: In recent years, research has shown that stress may be a significant factor in weight management and several other aspects of health. Because of this, the Ornish diet also recommends stress reduction techniques like meditation and mindfulness as another aspect of living a healthy lifestyle.
• No smoking: In large part because of the demonstrated connection to heart disease, the Ornish diet also requires the cessation of smoking.
• Social support: As with almost any significant lifestyle change, having a reliable social support system is crucial for success. Also, the fact that the diet revolves around plant-based proteins and whole foods makes it accessible for the whole family.

How Does the Ornish Diet Work?

Unlike diets that are designed to help you lose weight, the Ornish diet doesn’t generally have prescriptions for exactly what and how much to eat. There also aren’t any specific rules for how many proteins or carbohydrates you should consume. In fact, the diet doesn’t call for any calorie restriction at all unless you are actively trying to lose weight. Because the principles of the diet are geared toward overall healthy eating and lowering the risk of heart disease, that means there is a fair amount of flexibility in choosing foods within the guidelines. 

According to these guidelines (which are referred to collectively as the Ornish Lifestyle Medicine guidelines), the diet prefers foods as they are “found in nature” over processed foods that often have added refined carbs and other questionable compounds. Moreover, the diet makes a distinction between “good” carbs, fats, and proteins and “bad” carbs, fats, and proteins—which can essentially be understood as natural carbs over refined carbs, plant proteins over animal proteins, and healthy fats (like omega-3 fatty acids) over saturated and trans fats. 

Below are lists of the foods that are encouraged and discouraged on the Ornish diet:

Foods to Emphasize

• Fruits: Fresh, frozen, or canned fruits are meant to be a significant part of the diet.
• Vegetables: One rule of thumb is to fill half your plate with a wide variety of vegetables that are a mix of cooked and raw.
• Whole grains: Whole grains like brown rice, quinoa, whole wheat pasta, oatmeal, and whole-grain bread are all sources of “good” carbs.
• Legumes: Include beans, lentils, and peas in your meals to add both protein and fiber.
• Dairy: For those who want to include dairy, it should be non-fat or low-fat versions of yogurt, milk, and cheese.
• Eggs: While egg yolks contain most of the fat and cholesterol, the egg whites can be a great low-fat source of protein.

Foods to Limit or Avoid

• Fats: Saturated fats, trans fats, and any high-fat foods are the most important dietary elements to avoid with the Ornish diet. Only 10% of calories should come from fats like vegetable oil or fish oil.
• Red meat: Because of its high saturated fat content, red meat should be eliminated entirely or eaten in extremely limited quantities.
• Poultry: Poultry should similarly be avoided, especially higher-fat cuts like the wings or thighs.
• Fish: Fish is more acceptable than meat or poultry, but it should still be limited to small amounts and it should come from low-fat fish like cod or flounder.
• Nuts and seeds: Nuts and seeds are allowed because they have mainly unsaturated fat, but they should still be consumed sparingly.
• Processed foods: Many processed foods are high in fat or sugar and should be severely limited.
• Alcohol: As with most diets, alcohol consumption is not encouraged on the Ornish diet.

What Are the Health Benefits of the Ornish Diet?

The fact that the Ornish diet so strongly emphasizes whole, plant-based foods over processed foods makes it similar to other well-regarded eating patterns like the Mediterranean diet. Research over the last several decades has shown how the average American diet tends to be deficient in many of the healthy compounds that come from plants, so simply by increasing the intake of those compounds, you’re already eating in a healthier way. Apart from this general improvement in nutrition, the Ornish diet claims to provide several additional health benefits:

• Reverse heart disease: As noted earlier, the main thrust of the diet is to bolster heart health primarily by dramatically reducing fat intake and maintaining a moderate exercise habit. Dr. Ornish’s organization goes even further by claiming that following the diet can actually reverse heart disease. This is partly due to the high amount of dietary fiber that comes with so many plant-based foods; because in addition to improving digestive health, fiber can also lower the amount of “bad” cholesterol (LDL) found in the bloodstream. Also, the various foods recommended by the diet are high in minerals like calcium and potassium that are known to lower blood pressure.
• Reverse diabetes: The research has been clear for many years that a diet high in refined carbohydrates (some types of sugar) is a major risk factor for type 2 diabetes. This is because these kinds of foods increase blood sugar; over time, high blood sugar leads to problems with insulin, the hormone that regulates the amount of glucose in the bloodstream. What starts as reduced effectiveness of insulin (insulin resistance) can eventually become a permanent inability to produce sufficient insulin at all. A diet like the Ornish diet that is high in fiber and low in refined carbohydrates can prevent this from happening, but it can also somewhat improve the symptoms and management of diabetes.
• Reverse prostate cancer: Even though cancer has been the subject of countless research efforts over the last century, there is still much that doctors don’t understand about what causes it and where it shows up and how it progresses. Over these many years, however, lifestyle factors like diet and physical activity have seemed to become more relevant for researchers. One of the claims associated with the Ornish diet is that adhering to it may be able to reverse early stage prostate cancer. To the extent this might be true, it is believed to be in large part because of the antioxidant properties of many fruits and vegetables. Antioxidants are so named because they prevent oxidative stress, a physiological imbalance that occurs when there is an excess of harmful molecules called free radicals in the body. A diet high in antioxidants can thus theoretically prevent chronic diseases like cancer.

Can the Ornish Diet Lead to Weight Loss?

The particulars of the Ornish diet have been evolving since the 1970s, but improved heart health has always been the main purpose. Yet even if the diet has not been primarily organized around losing weight, the nature of the recommended foods and the other precepts are similar to some other diet plans that are aimed at weight loss. These are some of the aspects of the diet that make it a potential option for a weight loss plan:

• Low fat: Not all fat is bad of course, but the focus on eliminating trans and saturated fat is also helpful for weight loss purposes. Even besides the heart-related reasons for consuming less fat, fat in foods makes them calorically dense and relatively less filling. Limiting the amount of fat in your diet, regardless of which diet plan you select, can generally reduce the overall number of calories you consume.
• High fiber: Fiber is important for metabolic reasons, but it also is fundamentally indigestible; this makes it crucial for digestive health as well as increasing the feeling of fullness after eating. And these feelings of fullness and satiety are major factors in controlling calorie intake.
• Portion control: Though the Ornish diet doesn’t specify amounts of food or numbers of calories, it does recommend eating a variety of smaller meals throughout the day. This practice is encouraged because it can theoretically help you control food portions better and not be as driven by food cravings throughout the day.
• Nutrient density: Portion control is also possible because the foods highlighted on the Ornish diet all tend to be nutrient dense. This means that you can get necessary nutritional value from less food and fewer calories and are thus less likely to overeat.

What Do the Experts Say?

Laura Justice, MS, RD, LDN, a registered dietitian, offers some insight into commonly asked questions about the Ornish diet:

What are the pros and cons of the Ornish diet?

• As with any plant-based diet, it focuses on having mostly plants on your plate like fruits, vegetables, and whole grains, which we know our bodies thrive on. However, this diet does limit our fat intake to about 10% of calorie intake, which could cause deficiencies in certain vitamins that are fat soluble.  

What type of people may benefit from this diet, and who should avoid this?

• Those who must follow a low-fat diet due to absorption issues would benefit from this style diet otherwise the fabulous Mediterranean diet would fit the plant-based mold without worry of too little fat.  

What have you found people are generally unaware of when considering the Ornish diet?

• The Ornish diet does eliminate or drastically decrease the amount of certain food groups. You cannot eat meat, fish, poultry, refined carbs, packaged/processed foods, caffeine, or alcohol. The diet also suggests limiting nuts, seeds, egg whites, and dairy. These foods are valuable parts of our diet. You may need to take certain vitamin supplements to ensure you do not become deficient in fat soluble vitamins.

How much weight do people typically lose with the Ornish diet?

• A few 1-year studies show an average weight loss of around 5-7 lbs in 1 year. This diet is more geared toward eating the best foods you can to help prevent disease and other health conditions by focusing on fruits, vegetables, whole grains, legumes, and soy. 

For someone that might be considering the Ornish diet, what alternative options should they consider and why?

• The Mediterranean diet is a good all-encompassing diet that has been proven by research to improve and prevent some diseases (i.e. heart disease, diabetes, cancer) but does not limit your fat intake like the Ornish diet does. Those essential fats are important for our bodies to function properly while still prioritizing whole foods: plants (fruits, vegetables, legumes/beans, whole grains), lean meats, fish, unsaturated fats. It’s all about the balance of all of the food groups! 

Bottom Line

Dr. Ornish’s Preventive Medicine Research Institute has been the main organization doing research on the effectiveness of the Ornish diet. As such, there haven’t been many independent studies that specifically evaluate the diet. Nevertheless, general research about nutrition and weight loss does agree with some aspects of the diet, especially the benefits surrounding limits on saturated fat and refined carbohydrates. As far as some of the more sensational claims about reversing diabetes and prostate cancer, much more research needs to be done.

One aspect of the diet that remains somewhat controversial in the larger medical community is the efficacy of an overall low-fat diet. Low-fat diets were highly touted in the 1980s and 90s, but research on this topic in more recent years has called this approach into question. It may very well be, for instance, that the low-fat obsession of an earlier era worsened the obesity epidemic by encouraging people to swap fatty foods for highly processed foods that are loaded with refined sugars. The implication is that the worry about fat content made Americans more likely to eat foods that are actually worse from a metabolic perspective.

The bottom line: the Ornish diet has a number of central components that make it a great choice for eating generally healthier and improving some aspects of health. It isn’t, however, necessarily better or more effective than other diets that similarly highlight the importance of plant-based foods and limiting saturated fat. In terms of weight loss, the Ornish diet can be a useful framework for promoting a calorie deficit, but like most diets it will only help you lose weight if you are consistent with following it.

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