How does the Ornish diet work?

The Ornish diet is a low-fat, low-cholesterol eating plan that limits refined carbohydrates. It recommends that only 10% of daily calories come from fat, with a cholesterol intake of 10 milligrams or fewer, and excludes animal protein except for fat-free dairy products and egg whites.

Pharmacist and nutritional therapist Deborah Grayson, Practice With Confidence, Greater Manchester, UK explains that the Ornish diet is based on the following principles:

Michelle Routhenstein, Cardiology Dietitian, EntirelyNourished.com adds that non-fat milk products - such as yoghurt or milk - are allowed with a limit of two servings or less daily. Alcohol and caffeine are also restricted, though green tea is permitted by up to two cups a day.

A whole-food, low-fat, plant-based diet combined with regular exercise and less stress is generally believed to have various health benefits.

Dr Tracy Paeschke, preventive cardiologist, Colorado Springs, USA says this type of dietary and lifestyle approach lowers your chance of developing:

She says: "What's good for your heart is usually good for the rest of your body."

According to Routhenstein, research indicates that following this diet may lower inflammation, and potentially help those with a higher likelihood of developing Alzheimer’s disease.

Here are several food options that you can include in your diet following the Ornish diet plan:

• Fresh fruits - such as apples, bananas, blueberries, grapes, oranges, pears, pineapple, plums, raspberries, strawberries, watermelon.

• Vegetables - such as artichokes, asparagus, broccoli, Brussels sprouts, cabbage, cauliflower, celery, kale, mushrooms, peppers, peas, spinach.

• Fresh herbs - such as basil, chives, cilantro, mint, oregano, parsley, rosemary, sage, thyme.

• Legumes - black beans, black-eyed peas, baked beans, chickpeas, green peas, kidney beans, lentils, pinto beans, split peas.

• Wholegrain foods - barley, brown rice, oatmeal, quinoa, whole grain bread, whole grain cereals.

• Plant-based proteins - tofu, soybeans, soy products such as soy cheese, soy milk, soy yoghurt, egg whites.

• Nahrungsergänzungsmittel - multivitamin without iron, cholesterol-free fish oil capsules.

Here are several food options the Ornish diet advises you to restrict:

• Animal products - unless non-fat milk products and egg whites.

• High-fat foods - such as avocados, coconut, nuts, oils, seeds,

• Refined carbohydrates - such as baked goods, cakes, pastries, processed foods, sugar, sweets, white bread, white pasta, white rice.

• Alkohol - allowed in small amounts.

• Koffein - allowed two cups of green tea a day.

While the Ornish diet focuses more on overall health than on counting calories, it can indirectly contribute to weight loss.

Paeschke says: "Because the Ornish diet is a whole-food, plant-based diet low in oils, it's also low in calories and high in fibre - both of which help you lose weight and maintain your weight loss."

"It may be difficult to maintain weight loss after transitioning off the diet, especially if you revert to previous eating patterns," she explains. "The restrictive nature of the diet might also trigger unhealthy relationships with food or eating behaviours - especially where a history of eating disorders exists."

Although the Ornish diet's focus on plant-based foods and low-fat intake is good for heart health, it's important to consider its potential drawbacks.

Grayson explains that a low-fat diet that is this restrictive may lead to deficiencies in essential fatty acids, vitamins, and minerals found in healthy fats, such as omega-3 fatty acids from fish or avocados. The restriction of animal products and high-fat foods may result in lower protein intake unless carefully planned with a wide variety of plant-based protein sources.

"If you require a higher fat intake for medical reasons - for example, epilepsy - you may not find the Ornish diet suitable," she adds. "Low-fat diet plans may leave you feeling less full, potentially leading to increased hunger and overeating of carbohydrates.

Athletes or those with physically demanding jobs may also require more protein than the Ornish Diet typically provides. If you are pregnant or breastfeeding you require higher fat and protein intake for your baby's development and breast milk production."