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Health & Diet Terms Glossary
Agonist: An agonist is any substance that fits into a chemical receptor and can activate the receptor in a way similar to the substance it was designed for. For example, Cabergoline is a pharmaceutical dopamine agonist, so using Cabergoline gives one effects similar to increasing the level of endogenous dopamine. Antagonist: An antagonist is any substance that binds to a chemical receptor in such a way that it blocks activation of the receptor by the endogenous ligand. Yohimbine is an example of an alpha-2 adrenergic receptor antagonist; it prevents (or reduces) the ability of the catecholamines to activate the a2 receptor, thereby increasing a variety of hormones normally inhibited by it. Basal Metabolic Rate (BMR): The BMR is the body’s rate of oxygen consumption, as measured at rest, and after a prolonged period (usually 12 hours) without exercise or food. Resting Energy Expenditure, or REE, and also Sleeping Energy Expenditure (SEE), are often used as reasonable proxies for the BMR. Double Blind Trial: Double-blind is considered the Gold Standard in medical research. It means the study involves at least two groups–a test group and a placebo group–and was designed so that only the people running the study know which patients are in which group. The patients themselves don’t know, and neither do the clinicians treating them. This minimizes study bias, but it’s not perfect, of course. Sometimes, the caretakers or the patients can easily figure out which treatment group they’re in, based on their response to the treatment, and some treatments simply don’t lend themselves to being blinded, for example, a study of the effects of an exercise program vs. no exercise program. Exercise Energy Expenditure (EEE): The EEE is the increase in the body’s rate of oxygen consumption, during and following a bout of exercises, over and above the BMR or REE. That is, if your body normally burns 75 cals/hr at rest, and jogging increases it to 350 cals/hr, your EEE of jogging is 275 (350-75). Epidemiological Research: An observational (versus clinical) form of research whereby populations are investigated with regard to potential associations between lifestyle or genetic factors and various aspects of health, such as growth rate or incidence of particular diseases. While epidemiological research is a wonderful way to inspire ideas, it is not a conclusive form of research. For example, if we observed that a small tribe of people living on a remote island subsisted almost entirely on a diet of tree bark and were found to never contract cancer, we could develop a theory that tree bark is a powerful cancer preventative. If we then tested tree bark on people in a highly cancer-prone society and found no benefit, we might conclude that tree bark is useless against cancer, but we might be wrong! It may be that the people on the second island are genetically programmed for cancer and nothing will help them, while tree bark might work very well on yet a third population. We would have to “do more research” to find out. To reiterate, epidemiology is great for forming theories, but by itself, does not provide proof positive. The First Law of Thermodynamics: Energy can neither be created nor destroyed; it can only change forms. The application in the case of calorie balance being that every calorie consumed must either be transformed into another form of energy or stored as fat. In Vitro Research: In vitro comes from the Latin for “within the glass”, which pretty accurately describes it. In vitro research happens in a lab, usually in a test tube or petri dish, and not in a living body. In vitro research is important, because it can demonstrate the actual chemical reactions that are taking place when, for example, liver cells are exposed to a particular drug or type of bacteria. This helps the scientist to figure out why certain reactions take place and inspires ideas of how to change the results. Like epidemiological research, however, in vitro experiments are just a starting point. The chips may fall a completely different way when the myriad systems of a complex living being respond to that first initial reaction. In Vivo Research: In vivo comes from the Latin for “within the living”, and is the form of research your are probably most familiar with. An in vivo experiment involves live animals or people being studied under carefully specified conditions–a change in environment, a disease state, or the application of a drug or treatment. Non-Exercise Activity Thermogenesis (NEAT): NEAT is the increase in the body’s rate of oxygen consumption, during and following any activity that is not considered volitious exercise, over and above the BMR or REE, for example, housework, yardwork, typing, talking, showering, even watching television. All of these activities burn more calories than lying completely still. Thermic Effect of Food (TEF): The TEF is the percentage increase in the body’s rate of oxygen consumption, following a meal, as compared to the BMR. That is, if your body’s basal metabolic rate is x, and eating temporarily increases it to 1.1x, then your TEF, for that size meal and type of food, is 10%. TEF is sometimes expressed as the raw number of calories incrementally burned after a meal. Total Energy Expenditure (TEE): TEE is the body’s total energy consumption. It is often represented as the sum of its parts: TEE = REE + TEF + EEE + NEAT. When energy intake is not in balance with energy expenditure on a given day, the excess or deficit results in changes to body mass. TEE is often thought of as relatively constant, like the MPG of a car, but this is a very poor analogy; in fact, all the elements of TEE are rapidly adaptable to changes in the body’s state and environment.