The Ornish diet, created by the physician Dr. Dean Ornish, is a low-fat vegetarian diet. This diet encourages consumption of beans, fruits, vegetables, and whole grains, and limits intake of processed foods, high-fat dairy products, simple sugars, and alcohol.
There are two types of the Ornish diet; the reversal and the prevention diet. The reversal diet is recommended for people with existing heart disease desiring to reduce their risk of suffering a heart attack or other coronary heart disease event. The prevention diet is advocated for otherwise healthy individuals with levels of low-density lipoprotein (LDL) cholesterol greater than 150mg/dL or those with a ratio of total cholesterol to high-density lipoprotein (HDL) that is less than 3.0.
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Safety Safety definitions
Pregnancy And Lactation: There is insufficient reliable evidence about the safety of the Ornish diet. There's no reason to expect safety issues as long as patients' nutritional needs are met in pregnancy and lactation.
Effectiveness Effectiveness definitions
INSUFFICIENT RELIABLE EVIDENCE TO RATE
Cardiovascular disease. One clinical study suggests that patients following the Ornish diet in addition to exercise for one year may experience a decrease in angina and coronary stenosis.
Weight loss. Preliminary clinical research suggests that patients following the Ornish diet may lose 3.3 kg after one year.
More evidence is needed to rate the Ornish diet for these uses.
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
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Mechanism of action
The Ornish diet is based on the belief that metabolism was altered when early humans could not depend on regular meals due to the scarcity of regularly available food. The body, to preserve energy, would store any extra energy as fat. People in modern societies generally have unlimited access to food, but their bodies have not adapted to this new way of living.
It is theorized that if individuals eat only when hungry on the Ornish diet, without portion control, that their metabolism will stay the same, or perhaps increase. The high-fiber content also slows down the absorption of food into the digestive system, so a person feels full longer with small portions than if eating calorie-restricted small portions. The complex carbohydrates may help blood sugar remain more stable.
The Ornish diet also encourages long, slow exercise that is theorized to use body fat as fuel. Moderate exercise done on a regular basis is theorized to increase resting metabolism, while some have suggested that short periods of intense exercise decrease metabolism. Meditation in the Ornish diet is used as a way of quieting the mind, increasing self-awareness and coping with stress.