A healthy diet is one that is arrived at with the intent of improving or maintaining optimal health.

This usually involves consuming nutrients by eating the appropriate amounts from all of the food groups, including an adequate amount of water. Since human nutrition is complex, a healthy diet may vary widely, and is subject to an individual's genetic makeup, environment, and health. For around 20% of the human population, lack of food and malnutrition are the main impediments to healthy eating.Fact: date=March 2008 Conversely, people in developed countries have the opposite problem; they are more concerned about obesity.Fact: date=March 2008

Nutritional overview

1. Sufficient calories to maintain a person's metabolic and activity needs, but not so excessive as to result in fat storage greater than roughly 30% of body mass. For most people the recommended daily allowance of energy is 2,000 calories, but it depends on age, sex, height, weight, and physical activity. (see Body fat percentage)
2. Sufficient quantities of fat, including monounsaturated fat, polyunsaturated fat and saturated fat, with a balance of omega-6 and long-chain omega-3 lipids. The recommended daily allowance of fat is 65-80 grams.
3. Maintenance of a good ratio between carbohydrates and lipids (4:1): four grams of the first for one gram of the second.
4. Avoidance of excessive saturated fat (20grams recommended limit, although the "evidence" for this claim is forever in debate after the testimony of results provided by the Framingham Heart Study of 1948-1998)
5. Avoidance of trans fat.
6. Sufficient essential amino acids ("complete protein") to provide cellular replenishment and transport proteins. All essential amino acids are present in animals. A select few plants (such as soy and hemp) give all the essential acids. A combination of other plants may also provide all essential amino acids (except rice and beans which have limitations).
7. Essential micronutrients such as vitamins and certain minerals.
8. Avoiding directly poisonous (e.g. heavy metals) and carcinogenic (e.g. benzene) substances;
9. Avoiding foods contaminated by human pathogens (e.g. E. coli, tapeworm eggs);
10. Avoiding chronic high doses of certain foods that are benign or beneficial in small or occasional doses, such as
    • foods that may burden or exhaust normal functions (e.g. refined carbohydrates without adequate dietary fiber);
    • foods that may interfere at high doses with other body processes (e.g. refined table salt);
    • foods or substances with directly toxic properties at high chronic doses (e.g. ethyl alcohol).