In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. With the word diet, is often implied the use of specific intake of nutrition for health or weight-management reasons (with the two often being related). Although humans are omnivores, each culture and each person holds some food preferences or some food taboos, due to personal tastes or ethical reasons. Individual dietary choices may be more or less healthy. Proper nutrition requires ingestion and absorption of fiber, vitamins, minerals, and food energy in the form of carbohydrates, proteins, vegetable oils, and fats. Dietary habits and choices play a significant role in quality of life, health and longevity, and can define cultures and play a role in religion. Many people choose to forgo food from animal sources to varying degrees (flexitarianism, vegetarianism, veganism, fruitarianism) for health reasons, issues surrounding morality, or to reduce their personal impact on the environment. Raw foodism is another contemporary trend. These diets may require tuning or supplementation to meet ordinary nutritional needs. A particular diet may be chosen to seek weight loss or weight gain. Changing a subject’s dietary intake, or “going on a diet”, can change the energy balance and increase or decrease the amount of fat stored by the body. Some foods are specifically recommended, or even altered, for conformity to the requirements of a particular diet. These diets are often recommended in conjunction with exercise. Specific weight loss programs can be harmful to health, while others may be beneficial. A healthy diet may improve or maintain optimal health. In developed countries, affluence enables unconstrained caloric intake and possibly inappropriate food choices.It is recommended by many authorities that people maintain a normal weight (limiting consumption of energy-dense foods and sugary drinks), eat plant-based food, limit red and processed meat, and limit alcohol. However, there is no total consensus on what constitutes a healthy diet.