specified period of time (e.g., one consumed broccoli approximately three times per week in the course of the month). With this assessment tool, a typical nutrient intake of an individual can be determined. Food frequencies are quick to administer and not very tedious to analyze. They tend to be used in research studies. Correlation coefficients with food records for varying lengths of time range of 0.4 to 0.7. For further information, see Block (1982), Dwyer (1994), Longnecker et al. (1994), and Willett (1990).

Food lists are specialized tools in which foods are listed in various groupings by category (e.g., dairy foods) or dietary constituent (e.g., fat- or fiber-containing foods) to learn subjects' intake of particular kinds of foods or nutrients. Information on portion sizes, frequency of consumption, and method of preparation within each group is also obtained. Food lists are useful in the clinical setting as a quick and inexpensive means of assessing diets and identifying areas where the subject might benefit from dietary counseling.

An increasing amount of computer software is available containing information on the nutrient composition of foods. Features and price vary among programs. Some are available to the public for self-assessments, while the more sophisticated and feature-laden programs are marketed to health-care providers. The programs are used to calculate the nutrient content of a person's diet, usually comparing nutrient intake to a reference such as Recommended Dietary Allowances (RDAs); they are of particular benefit because they can perform the calculations in seconds and provide immediate feedback on the results. The size of the nutrient database and data-analysis capabilities of the programs vary tremendously, so the validity and reliability of these programs vary.

Health behaviors are difficult to measure, and physical activity is no exception. Existing methods, while relatively crude, nonetheless provide valid and reliable estimates of participation in physical activity and total energy expenditure. The most valid methods of physical activity assessment (doubly-labeled water, direct calorimetry, individual observation, and electronic monitoring) are complicated, technically daunting, intrusive, and expensive, and they are not feasible for use in weight-management