A healthy diet is one that helps maintain or improve general health. It is important for lowering many chronic health risks, such as obesity, heart disease, diabetes, hypertension and cancer. A healthy diet involves consuming appropriate amounts

of all essential nutrients and an adequate amount of water. Nutrients can be obtained from many different foods, so there are numerous diets that may be considered healthy. A healthy diet needs to have a balance of macronutrients (fats, proteins, and carbohydrates), calories to support energy needs, and micronutrients to meet the needs for human nutrition without inducing toxicity or excessive weight gain from consuming excessive amounts.

The Atkins Diet

The Atkins Diet involves the restriction of carbohydrates in ones diet causing the body's metabolism to switch from burning glucose as fuel to burning stored body fat, sending the body into a state of ketosis. Ketosis causes a person to get their energy from ketones, which also causes you to feel less hungry. Carbohydrate consumption must be <40 grams/day (= 1 slice of bread) for ketosis to occur.

Strengths

• Allowed to eat rich foods
• When in ketosis you feel less hungry and more satisfied

Limitations

• Ketosis causes unusual breath odor and constipation
• There is worry that the diet promotes heart disease and there is a potential loss of bone and it is not recommended for people with liver and kidney problems due to the high amounts of protein.
• The preferred source of energy for the brain is glucose, which is decreased in a low-carbohydrate diet

Ornish Diet

The Ornish Diet is a fat restricting diet (less than 10% of calories from fat) focusing on eating high amounts of fiber, and following a low-fat vegetarian diet. The Ornish diet recommends combining the diet with exercise that allows the body’s fat burning mechanism to work most effectively. The philosophy is focused less on restricting calories but by watching the ones consumed, by recommending foods that can be eaten all the time, some of the time and none of the time. Foods that can be eaten whenever you are hungry, until you are full are:

• Beans and legumes, fruits, grains and vegetables

Foods eaten in moderation are:

• Nonfat dairy products – skim milk, nonfat yogurt, nonfat cheese, nonfat sour cream and egg whites

Foods to avoid

• Meats of all kinds – if can’t give up, only eat minimally
• Oils and oil-containing products (margarine and most salad dressings)
• Avocados, olives, nuts and seeds, dairy products (other than non-fat ones)
• Simple sugar and simple sugar derivatives (honey, molassess, corn syrup, and high-fructose syrup)
• Alcohol
• Anything commercially prepared that has more than 2 grams of fat per serving

Suggests eating a lot of little meals because this diet makes you feel hungry more often, which will help you feel full faster and you’ll eat more food without increasing the number of calories.

Strengths

• Does not restrict calories
• Doesn’t slow down metabolism
• Recommends regular exercise, yoga and meditation along with the diet
• Has been associated with a reversal of coronary blockage

Weakness

• Very restrictive
• You will feel hungrier and need to eat more food (but less calories)

(wikipedia)