stomach at the training site should be provided with fluids during and immediately after training as well as food after training. Similarly, following competition or training for competition, athletes should rehydrate and consume a high carbohydrate meal (ACSM, 2000). For the healthy individual, the amount and intensity of exercise recommended is unlikely to lead to glycogen depletion, dehydration, or water intoxication. Nonetheless, timing of post-exercise meals to promote restoration of glycogen reserves and other anabolic processes can benefit resumption of normal daily activities.

Physical exercise has the potential to cause overuse injuries to muscles, bones, and joints as well as injuries caused by accidents. Additionally, pre-existing conditions can be aggravated upon initiation of a physical activity program, and chronic, repetitive activities can result in injuries. For instance, running can result in injuries to muscles and joints of the lower limbs and back, swimming can cause or irritate shoulder injuries, and cycling can cause or worsen problems to the hands, back, or buttocks. Fortunately, the recommendation in this report to accumulate a given amount of activity does not depend on any particular exercise or sports form. Hence, the activity recommendation can be implemented in spite of possible mild, localized injuries by varying the types of exercise (e.g., walking instead of jogging). Recalling the dictum of “do no harm,” the physical activity recommendations in this report are intended to be healthful and invigorating. Activity-related injuries are always frustrating and often avoidable, but they do occur and need to be resolved in the interest of long-term general health and short-term physical fitness.

Physical activity results in conversion of the potential chemical energy in carbohydrates and fats to mechanical energy, but in this process most (~ 75 percent) of the energy released appears as heat (Brooks et al., 2000). Evaporative heat loss from sweat is the main mechanism by which humans prevent hyperthermia and heat injuries during exercise. Unfortunately, the loss of body water as sweat during exercise may be greater than what can be replaced during the activity, even if people drink ad libitum or are on a planned diet. Hence, exercise may result in dehydration that increases

Front Matter (R1-R26)

Summary (1-20)

1. Introduction to Dietary Reference Intakes (21-37)

2. Methods and Approaches Used (38-52)

3. Relationship of Macronutrients and Physical Activity to Chronic Disease (53-83)

4. A Model for the Development of Tolerable Upper Intake Levels (84-106)

5. Energy (107-264)

6. Dietary Carbohydrates: Sugars and Starches (265-338)

7. Dietary, Functional, and Total Fiber (339-421)

8. Dietary Fats: Total Fat and Fatty Acids (422-541)

9. Cholesterol (542-588)

10. Protein and Amino Acids (589-768)

11. Macronutrients and Healthful Diets (769-879)

12. Physical Activity (880-935)

13. Applications of Dietary Reference Intakes for Macronutrients (936-967)

14. A Research Agenda (968-971)

Appendix A: Glossary and Acronyms (972-977)

Appendix B: Origin and Framework of the Development of Dietary Reference Intakes (978-984)

Appendix C: Acknowledgments (985-987)

Appendix D: Dietary Intake Data from the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994 (988-1027)

Appendix E: Dietary Intake Data from the Continuing Survey of Food Intakes by Individuals (CSFII) 1994-1996, 1998 (1028-1065)

Appendix F: Canadian Dietary Intake Data, 1990-1997 (1066-1075)

Appendix G: Special Analyses for Dietary Fats (1076-1077)

Appendix H: Body Composition Data Based on the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994 (1078-1103)

Appendix I: Doubly Labeled Water Data Used to Predict Energy Expenditure (1104-1202)

Appendix J: Association of Added Sugar Intake and Intake of Other Nutrients (1203-1225)

Appendix K: Data Comparing Carbohydrate Intake to Intake of Other Nutrients from the Continuing Survey of Food Intakes by Individuals (CSFII), 1994-1996, 1998 (1226-1243)

Appendix L: Options for Dealing with Uncertainties (1244-1249)

Appendix M: Nitrogen Balance Studies Used to Estimate the Protein Requirements in Adults (1250-1258)

Biographical Sketches of Panel and Subcommittee Members (1259-1274)

Index (1275-1318)

Summary Tables, Dietary Reference Intakes (1319-1331)