Common Terms D-G

Dehydration (hypohydration) is defined as excessive loss of body fluid. It is literally the removal of water (Ancient Greek: ὕδωρ hýdōr) from an object, however in physiological terms, it entails a deficiency of fluid within an organism.

There are three main types of dehydration; hypotonic (primarily a loss of electrolytes, sodium in particular), hypertonic (primarily a loss of water), and isotonic (equal loss of water and electrolytes).

In humans, the most commonly seen type of dehydration by far is isotonic (isonatraemic) dehydration which effectively equates with hypovolaemia (described below), but distinction of isotonic from hypotonic or hypertonic dehydration may be important when treating people who become dehydrated. It is important to understand (physiologically speaking) that dehydration, despite the name, does not simply mean loss of water, as water and solutes (mainly sodium) are usually lost in roughly equal quantities to how they exist in blood plasma.

Depression is a state of low mood and aversion to activity. Some consider it a dysfunction, while others see it as an adaptive defense mechanism. The Diagnostic and Statistical Manual of Mental Disorders defines a depressed person as experiencing feelings of sadness, helplessness and hopelessness. In traditional colloquy, feeling "depressed" is often synonymous with feeling "sad", but both clinical depression and non-clinical depression can also refer to a conglomeration of more than one feeling.

Diabetes mellitus-often simply referred to as diabetes—is a condition in which a person has a high blood sugar (glucose) level as a result of the body either not producing enough insulin, or because body cells do not properly respond to the insulin that is produced. Insulin is a hormone produced in the pancreas which enables body cells to absorb glucose, to turn into energy. If the body cells do not absorb the glucose, the glucose accumulates in the blood (hyperglycemia), leading to various potential medical complications.

There are many types of diabetes, the most common of which are:

Type 1 diabetes: results from the body's failure to produce insulin, and presently requires the person to inject insulin.
Type 2 diabetes: results from insulin resistance, a condition in which cells fail to use insulin properly, sometimes combined with an absolute insulin deficiency.
Gestational diabetes: is when pregnant women, who have never had diabetes before, have a high blood glucose level during pregnancy. It may precede development of type 2 DM.

A dietitian or dietician (dietitian is the official spelling used within the dietetics profession) is an expert in food and nutrition. Dieticians: Dietitians help promote good health through proper eating. They supervise the preparation and service of food, develop modified diets, participate in research, and educate individuals and groups on good nutritional habits. In a medical setting, a dietitian may provide specific artificial nutritional needs to patients unable to consume food normally. Dietary modification to address medical issues involving dietary intake is also a major part of dietetics. The goals of the dietary department are to provide medical nutritional intervention, obtain, prepare, and serve flavorsome, attractive, and nutritious food to patients, family members, and health care providers.

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be absorbed, for instance, into a blood stream. Digestion is a form of catabolism; a break-down of macro food molecules to smaller ones.

In mammals, food enters the mouth, being chewed by teeth, with chemical processing beginning with chemicals in the saliva from the salivary glands. Then it travels down the esophagus into the stomach, where acid both kills most contaminating microorganisms and begins mechanical break down of some food (eg denaturation of protein), and chemical alteration of some. After some time (typically an hour or two in humans, 4-6 hours in dogs, somewhat shorter duration in house cats, ...), the results go through the small intestine, through the large intestine, and are excreted during defecation.

Other organisms use different mechanisms to digest food.

Discrimination is a sociological term referring to the treatment taken toward or against a person of a certain group that is taken in consideration based on class or category. The United Nations explains: "Discriminatory behaviors take many forms, but they all involve some form of exclusion or rejection." Discriminatory laws such as redlining have existed in many countries. In some countries, controversial attempts such as racial quotas have been used to redress negative effects of discrimination.

A diuretic is any drug that elevates the rate of urination and thus provides a means of forced diuresis. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.

A dumbbell is a piece of equipment used in weight training, and is a type of free weight. They can be used individually or in pairs (one for each hand).

Endorphins are endogenous opioid polypeptide compounds. They are produced by the pituitary gland and the hypothalamus in vertebrates during exercise, excitement, pain, consumption of spicy food and orgasm, and they resemble the opiates in their abilities to produce analgesia and a feeling of well-being. Endorphins work as "natural pain relievers."

Endurance (also called sufferance) is the ability for an animal to exert itself for a long period of time. In humans, it is usually used in aerobic or anaerobic exercise. The definition of 'long' varies according to the type of exertion - minutes for high intensity anaerobic exercise, hours or days for low intensity. Training for endurance can have a negative impact on the ability to exert strength unless an individual also undertakes resistance training to counteract this effect.

In epidemiology, an epidemic (from Greek epi- upon + demos people) occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is "expected," based on recent experience (the number of new cases in the population during a specified period of time is called the "incidence rate"). (An epizootic is the analogous circumstance within an animal population.) In recent usages, the disease is not required to be communicable; examples include cancer or heart disease. Another example includes the infamous Black Plague of the Middle Ages.

Essential fatty acids, or EFAs, are fatty acids that cannot be constructed within an organism (generally all references are to humans) from other components by any known chemical pathways, and therefore must be obtained from the diet. The term refers to fatty acids involved in biological processes, and not those which may just play a role as fuel. As many of the compounds created from essential fatty acids can be taken directly in the diet, it is possible that the amounts required in the diet (if any) are overestimated. It is also possible they can be underestimated as organisms can still survive in non-ideal, malnourished conditions.

There are two families of EFAs: ω-3 (or omega-3 or n−3) and ω-6 (omega-6, n−6). Fats from each of these families are essential, as the body can convert one omega-3 to another omega-3, for example, but cannot create an omega-3 from omega-6 or saturated fats.[citation needed] They were originally designated as Vitamin F when they were discovered as essential nutrients in 1923. In 1930, work by Burr, Burr and Miller showed that they are better classified with the fats than with the vitamins.

An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet.

Food faddism and fad diet usually refer to idiosyncratic diets and eating patterns.

The term "food fad" may also be used with a positive connotation, namely, to describe the short term popularity among restaurants and consumers of an ingredient, dish, or preparation technique.

Fartlek, which means "speed play" in Swedish, is a form of conditioning which puts stress mainly on the aerobic energy system due to the continuous nature of the exercise. The difference between this type of training and continuous training is that the intensity or speed of the exercise varies, meaning that aerobic and anaerobic systems can be put under stress. Most fartlek sessions last a minimum of 45 minutes and can vary from aerobic walking to anaerobic sprinting. Fartlek training is generally associated with running, but can include almost any kind of exercise.

The food guide pyramid (historical) known as the food pyramid, and formally titled the Improved American Food Guide Pyramid, was published by the USDA (United States Department of Agriculture) in 1992 to replace the earlier food groups classification system. The food guide pyramid suggested optimal nutrition guidelines for each food category, per day, using a mnemonic graphic of a pyramid with horizontal dividing lines to represent suggested percentages of the daily diet for each food group. Currently published every five years, an update to the 2005 system is expected in 2010.

A gastrectomy is a partial or full surgical removal of the stomach.

Gastric bypass procedures (GBP) are any of a group of similar operations used to treat morbid obesity—the severe accumulation of excess weight as fatty tissue—and the health problems (comorbidities) it causes. Bariatric surgery is the term encompassing all of the surgical treatments for morbid obesity, not just gastric bypasses, which make up only one class of such operations.

Gastroesophageal reflux disease (GERD), gastro-oesophageal reflux disease (GORD), gastric reflux disease, or acid reflux disease is defined as chronic symptoms or mucosal damage produced by the abnormal reflux in the oesophagus.

This is commonly due to transient or permanent changes in the barrier between the oesophagus and the stomach. This can be due to incompetence of the lower esophageal sphincter, transient lower oesophageal sphincter relaxation, impaired expulsion of gastric reflux from the oesophagus, or a hiatal hernia. Respiratory and laryngeal manifestations of GERD are commonly referred to as extraesophageal reflux disease (EERD).

Glucose (Glc), a monosaccharide (or simple sugar) also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate. Glucose is one of the main products of photosynthesis and starts cellular respiration in both prokaryotes (bacteria and archaea) and eukaryotes (animals, plants, fungi, and protists).