Diet

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List of terms related to Diet

In nutrition, the diet is the sum of the food consumed by a person. Dietary habits are the choices individual or culture makes when choosing what foods to eat.

Although humans are omnivores, each culture holds some food preferences and some food taboos. Individual dietary choices may be more or less healthy. Proper nutrition requires vitamins, minerals, and fuel in the form of carbohydrates, proteins, and fats. Dietary habits play a significant role in the health and mortality of all humans. Dietary choices can also define cultures and play a role in religion.

Cultural dietary choices

Some cultures and religions have restrictions concerning what foods are acceptable in a diet. For example, only Kosher foods are permitted by Judaism, and Halal/Haram foods by Islam, in the diet of believers.[1] In addition, the dietary choices of different countries or regions have different characteristics. For instance, Americans eat more red meat than people in most other countries, and Japanese eat more fish and rice. Rice and beans are typical parts of a diet in Latin-American countries, while lentils and pita bread are typical in the Middle East. This is highly related to a culture's cuisine.

Concerns about foodborne illness have long influenced diet. Traditionally humans have learned to avoid foods that induce acute illness. Some believe that this is the underlying rationale behind some traditional religious dietary requirements.

Individual dietary choices

Many individuals choose to limit what foods they eat for reasons of health, morality, or other factors. Additionally, many people choose to forgo food from animal sources to varying degrees; see vegetarianism, veganism, fruitarianism, living foods diet, and raw foodism.

The nutrient content of diets in industrialised countries contain more animal fat, sugar, energy, alcohol and less dietary fiber, carbohydrates and antioxidants. Contemporary changes to work, family and exercise patterns, together with concerns about the effect of nutrition and overeating on human health and mortality are all having an effect on traditional eating habits. Physicians and alternative medicine practitioners may recommend changes to diet as part of their recommendations for treatment.[2]

More recently, dietary habits have been influenced by the concerns that some people have about possible impacts on health or the environment from genetically modified food.[3] Further concerns about the impact of industrial farming on animal welfare, human health and the environment are also having an effect on contemporary human dietary habits. This has led to the emergence of a counterculture with a preference for organic and local food.[4]

Diets for weight management

A particular diet may be chosen to seek weight gain, weight loss, sports training, cardio-vascular health, avoidance of cancers, food allergies and for other reasons. 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. Foods intended to help produce weight loss are frequently labeled "diet foods". These diets are often recommended in conjuction with exercise. A very low calorie diet under careful physician supervision with 800-1000 calories by eliminating or avoiding as much of the empty calories as possible is recommended for weight loss in combination with other measures forweight loss.

Dietary health

Imbalances between the consumed fuels and expended energy results in either starvation or excessive reserves of adipose tissue, known as body fat.[5] Poor intake of various vitamins and minerals can lead to diseases which can have far-reaching effects on health. For instance, 30% of the world's population either has, or is at risk for developing, Iodine deficiency.[6] It is estimated that at least 3 million children are blind due to vitamin A deficiency.[7] Vitamin C deficiency results in scurvy.[8] Calcium, Vitamin D and Phosphorus are inter-related; the consumption of each may affect the absorption of the others. Kwashiorkor and marasmus are childhood disorders caused by lack of dietary protein.[9] Obesity, a serious problem in the western world, leads to higher chances of developing heart disease, diabetes, and many other diseases.[10]

Eating disorders are a group of mental disorders that interfere with normal food consumption. They often affect people with a negative body image.


Dieting is the practice of eating (and drinking) in a regulated fashion to achieve a particular, short-term objective. This is distinct from the more basic concept of "diet," which addresses tie longer-term and more generic habit of nutritional consumption. For example, a vegan eats a diet completely without animal products, including milk; but while this is a diet, it is not "dieting."

The most common objective of dieting is loss of excess body fat. Some dieting is prescribed to achieve particular medical objectives, such as sodium-free diets, bland diets and soft food diets, while some dieting is actually designed to increase body fat and/or muscle weight gain.

Types of diets

There are several kinds of diets:

  • Weight-loss diets restrict the intake of specific foods, or food in general, to reduce body weight. What works to reduce body weight for one person will not necessarily work for another, due to metabolic differences and lifestyle factors. Also, it's important to note that short-term dieting does not necessarily lead to weight loss in the long term. Reducing the body's food supply causes it to stockpile excess fat as a starvation response once normal eating is resumed - meaning crash dieting leads to small short-term weight loss, then an increase in weight shortly afterwards.
  • Many professional athletes impose weight-gain diets on themselves. For example, wrestlers may overeat in order to achieve a higher weight class. American football players may try to "bulk up" through weight-gain diets in order to gain an advantage on the field with a higher mass.
  • Medical conditions often require the following of special diets. Each of these diets will specifically include or exclude or regulate certain chemicals (and the foods that contain them). For example, a person who has diabetes is often on a diet designed to carefully manage his or her blood sugar level. Epileptics are often put on the Ketogenic Diet. Sufferers of celiac disease must follow a gluten-free diet, the lactose-intolerant are advised to omit milk products, and people with kidney disease must follow a strict low-sodium diet to ease the strain on their kidneys. Treatment of mild hypertension includes adhering to a diet rich in fruits and vegetables and low in fat and sodium. This diet may be tailored to focus on weight loss if that is necessary to control blood pressure. Some people show allergic reactions to different types of food. They may include but are not limited to wheat flour, nuts, various types of fruit, egg white etc. These foods are to be avoided in such cases. A special diet may be necessary to prevent health problems.

History of targeted dieting

The practice of dieting in order to lose weight is ancient. Throughout the 17th and 18th centuries, physicians and patients regulated their food carefully, in order to prevent disease. In the 19th century, as the scientific classification of foods took shape, doctors and scientists began experimenting with targeted diets.

William Banting is one of the first people known to have successfully lost weight by developing a targeted diet, circa 1863, by targeting carbohydrates. The low carbohydrate diet, sometimes marketed today as the Atkins Diet, remains popular today.

Thermoregulation

According to the principles of thermoregulation, humans are endotherms. We expend energy to maintain our blood temperature at body temperature, which is about 37 °C (98.6 °F). This is accomplished by metabolism and blood circulation, by shivering to stay warm, and by sweating to stay cool.

In addition to thermoregulation, humans expend energy keeping the vital organs (especially the lungs, heart and brain) functioning. Except when sleeping, our skeletal muscles are working, typically to maintain upright posture. The average work done just to stay alive is the basal metabolic rate, which (for humans) is about 1 watt per kilogram of body mass. Thus, an average man of 75 kilograms who just rests (or only walks a few steps) burns about 75 watts (continuously), or about 6,500 kilojoules (1,500 Calories) per day.

Physical exercise (with an example)

Physical exercise is an important complement to dieting in securing weight loss. Aerobic exercise is also an important part of maintaining normal good health, especially the muscular strength of the heart. To be useful, aerobic exercise requires maintaining a target heart rate of above 50 percent of one's maximum heart rate for 30 minutes, at least 3 times a week. Brisk walking can accomplish this.

The ability of a few hours a week of exercise to contribute to weight loss can be overestimated. To illustrate, consider a 100-kilogram man who wants to lose 10 kilograms and assume that he eats just enough to maintain his weight (at rest), so that weight loss can only come from exercise. Those 10 kilograms converted to work are equivalent to about 350 megajoules. (We use an approximation of the standard 37 kilojoules or 9 calories per gram of fat.) Now assume that his chosen exercise is stairclimbing and that he is 20 percent efficient at converting chemical energy into mechanical work (this is within measured ranges). To lose the weight, he must ascend 70 kilometers. A man of normal fitness (like him) will be tired after 500 meters of climbing (about 150 flights of stairs), so he needs to exercise every day for 140 days (to reach his target).

The minimum safe dietary energy intake (without medical supervision) is 75 percent of that needed to maintain basal metabolism. For our hypothetical 100-kilogram man, that minimum is about 5,700 kilojoules (1,300 calories) per day. By combining daily aerobic exercise with a weight-loss diet, he would be able to lose 10 kilograms in half the time (70 days). Of course, the described regime is more rigorous than would be desirable or advisable for many persons. Therefore, under an effective but more manageable weight-loss program, losing 10 kilograms (about 20 pounds) may take as long as 6 months.

There are also some easy ways for people to exercise, such as walking rather than driving, climbing stairs instead of taking elevators, doing more housework with fewer power tools, or parking their cars farther and walking to school or the office.

Fat loss versus muscle loss (and the importance of exercise and protein intake)

It is important to understand the difference between weight loss and fat loss. Weight loss typically involves the loss of fat, water and muscle. A dieter can lose weight without losing much fat. Ideally, overweight people should seek to lose fat and preserve muscle, since muscle burns more calories than fat. Generally, the more muscle mass one has, the higher one's metabolism is, resulting in more calories being burned, even at rest. Since muscles are more dense than fat, muscle loss results in little loss of physical bulk compared with fat loss. To determine whether weight loss is due to fat, various methods of measuring body fat percentage have been developed.

Muscle loss during weight loss can be restricted by regularly lifting weights (or doing push-ups and other strength-oriented calisthenics) and by maintaining sufficient protein intake. According to the National Academy of Sciences, the Dietary Reference Intake for protein is "0.8 grams per kilogram of body weight for adults."

Those on low-carbohydrate diets, and those doing particularly strenuous exercise, may wish to increase their protein intake. However, there may be risks involved. According to the American Heart Association, excessive protein