Nutrition and Physical Activity: Key Concepts for College Nutrition Students

Nutrition and Physical Activity

Energy Needs for Physical Activity

Physical activity increases the body's energy requirements. The amount of energy needed depends on several factors:

• Intensity, Duration, and Frequency of Activity: More intense, longer, or more frequent exercise increases energy needs.

• Characteristics of the Exerciser: Age, sex, body size, and fitness level affect energy requirements.

• Location: Environmental factors such as temperature and altitude can influence energy expenditure.

For athletes, both the source and amount of dietary energy are important for optimal performance and recovery.

Macronutrient Distribution for Athletes

The recommended proportion of energy intake for athletes and healthy individuals is:

• Carbohydrates: 45–65% of total energy intake

• Fat: 20–35% of total energy intake

• Protein: 10–35% of total energy intake (athletes may require amounts at the higher end, which can be met through food)

Micronutrients of Special Concern for Athletes

• B Vitamins: Essential for energy metabolism.

• Antioxidant Vitamins (C and E): Help protect cells from oxidative damage caused by increased oxygen use during exercise.

• Iron: Important for oxygen transport; deficiency can lead to anemia and impaired performance.

• Calcium: Necessary for bone health and muscle function.

Female Athlete Triad

The Female Athlete Triad is a syndrome observed in physically active females, characterized by:

• Restrictive Eating Patterns: May include disordered eating or eating disorders.

• Amenorrhea: Absence of menstruation due to low energy availability.

• Bone Formation Issues: Reduced bone density, increasing risk of osteoporosis and fractures.

Sports Anemia

Sports anemia is a temporary condition seen in athletes, especially those engaged in endurance sports. It is characterized by:

• Reduced hemoglobin levels due to increased plasma volume, which dilutes red blood cells.

• This adaptation is generally beneficial and does not indicate true iron-deficiency anemia.

Fluid Needs for Physical Activity

Proper hydration is essential for exercise performance and safety. Fluids serve to:

• Eliminate heat through sweat and evaporation

• Transport oxygen and nutrients to muscles

• Remove metabolic waste products such as lactic acid

At rest in a temperate climate, the body loses about 4.5 cups (approximately 1.1 liters) of water per day through evaporation from the skin and lungs.

Dehydration

• Occurs when fluid losses are not adequately replaced.

• Impaired heat dissipation can lead to increased body temperature, reduced exercise performance, and health risks such as heat exhaustion or heat stroke.

Humidex and Heat-Related Illness

• The humidex is an index that combines temperature and humidity to estimate the risk of heat-related illness during physical activity.

Recommended Fluid Intake

Timing	Recommended Intake
Before Exercise	Drink fluids to ensure proper hydration
During Exercise	Consume fluids regularly to replace losses (amount varies with intensity and environment)
After Exercise	Replenish fluids and electrolytes lost through sweat

Additional info: Specific values for fluid intake depend on body size, exercise intensity, and environmental conditions. Table 13.3 in the textbook provides detailed recommendations.

Hyponatremia

• Hyponatremia is a condition caused by drinking excessive amounts of water, leading to dangerously low sodium levels in the blood.

• Symptoms include nausea, headache, confusion, and in severe cases, seizures or coma.

Nutritional Strategies for Exercise

• Maximize Glycogen Storage: Glycogen is the storage form of carbohydrate in muscles and liver, essential for endurance performance.

• Carbohydrate Loading: A strategy to increase muscle glycogen stores before endurance events; not beneficial for activities lasting 90 minutes or less.

Timing of Nutrient Intake

Timing	Recommendations
Pre-Exercise	Consume fluids and a meal with 60–70% carbohydrates 2–3 hours before the event
During Exercise	Maintain hydration and consume 30–60g carbohydrates per hour (after the first hour)
After Exercise	Replenish fluids, electrolytes, glycogen, and protein for muscle repair

Label Literacy: Sports Bars

• Sports bars may contain added vitamins and minerals not always listed on the label.

• It is important to read nutrition labels carefully to understand the nutrient content and added ingredients.