Nutrition & Physical Activity: Videos & Practice Problems

Physical activity increases macronutrient needs, especially carbohydrates and proteins, to support energy production via glycogen and muscle repair. High-performance athletes require 5–12 g/kg carbs and 1.2–2.4 g/kg protein daily, while fat intake remains 0.8–1.2 g/kg. Meal timing is crucial: consume carbs and proteins 2–4 hours before exercise, simple carbs during prolonged activity, and a 3:1 carb-to-protein meal within 30–45 minutes post-exercise to optimize glycogen replenishment and muscle recovery. Micronutrients like vitamins C, E, B-complex, calcium, and iron are vital for antioxidant defense, metabolism, muscle contraction, and oxygen transport, supporting physical fitness and ATP synthesis.

How Does Physical Activity Affect Macronutrient Needs?

Physical activity has a significant impact on macronutrient needs, particularly for carbohydrates, proteins, and fats. While engaging in physical activity does increase energy and macronutrient requirements, most individuals do not need to exceed typical dietary guidelines. It is primarily high-performance competitive athletes who may benefit from higher intakes of carbohydrates and proteins.

For non-athletes and moderately active individuals, carbohydrate requirements range from 3 to 5 grams per kilogram of body weight per day. In contrast, high-performance athletes may require between 5 and 12 grams per kilogram. This increased carbohydrate intake is essential for replenishing glycogen stores, which serve as a critical energy source during high-intensity exercise.

When it comes to protein, non-athletes typically need about 0.8 grams per kilogram, while high-performance athletes may require between 1.2 and 2.4 grams per kilogram. This higher protein intake supports muscle growth and repair, which is vital for athletes engaged in rigorous training.

Interestingly, fat requirements remain consistent across both groups, with both non-athletes and high-performance athletes needing between 0.8 and 1.2 grams of fat per kilogram of body weight per day. This is logical, as fats are not the primary energy source during high-intensity activities. Additionally, increasing the intake of saturated and trans fats can elevate the risk of disease, even among athletes.

In summary, while physical activity does elevate macronutrient needs, only those engaged in high-performance sports may require significant increases in carbohydrate and protein intake, while fat requirements remain stable across different activity levels.

Which of the following statements is true for elite athletes?

• A. They have higher fat requirements than the average person because they need more energy.
• B. They have higher protein requirements than the average person to aid in growth, recovery, & repair.
• C. Their carbohydrate needs are the same as the general population.
• D. Options b) & c).
• E. All of the above.

Answer: (B)

Timing Meals Around Exercise

Timing meals around exercise is crucial for optimizing performance and recovery. Before exercising, it's essential to consume a meal rich in carbohydrates and proteins. Carbohydrates are the primary energy source during high-intensity activities, while proteins support muscle preservation, growth, and repair. However, it's important to avoid eating a large meal immediately before exercising, as a full stomach can hinder performance. Generally, allowing two to four hours for digestion is recommended, making it ideal to eat a carbohydrate and protein-rich meal within this timeframe.

Endurance athletes often use a strategy called carbohydrate loading to maximize glycogen stores in their muscles in the days leading up to an event. During exercise, particularly for sessions lasting longer than one hour, it's beneficial to consume simple carbohydrates in small amounts. This can be achieved through sports drinks, bars, or light snacks like crackers, ideally every fifteen to twenty minutes, to maintain energy levels.

Post-exercise nutrition is equally important. About thirty to forty-five minutes after exercising, aim for a meal that has a carbohydrate to protein ratio of 3:1. This means that approximately three-fourths of the meal should consist of carbohydrates, while one-fourth should be protein. This specific timing is critical as the body is most receptive to replenishing glycogen stores and promoting muscle recovery during this window.

In summary, proper meal timing around exercise involves strategic consumption of carbohydrates and proteins before, during, and after workouts to enhance performance and recovery.

Femi has just played a full 90-minute soccer game. Which of the following would be the most beneficial for him to eat 45 minutes after the game has ended?

• A. A grilled chicken breast with steamed broccoli.
• B. A salad with lettuce, spinach, carrots, tomatoes, avocadoes, & an olive oil vinaigrette.
• C. A whole-wheat bagel with peanut butter & a glass of chocolate milk.
• D. Pasta with tomato sauce.

Answer: (C)

Who would gain the most benefit from carbohydrate loading?

• A. Brian, who is planning on running a 5k tomorrow morning.
• B. Natalie, who is preparing for an iron man triathlon the next day.
• C. Steve, who is about to play basketball for 45 minutes.
• D. Christine, a track athlete who has a 400-meter race coming up.

Answer: (A)

The Role of Micronutrients in Athletic Performance

Micronutrients play a crucial role in enhancing athletic performance, especially for physically active individuals who may have slightly increased requirements. Vitamins E and C are essential antioxidants that help neutralize free radicals produced during physical activity, protecting the body from oxidative stress. Additionally, B vitamins are vital for metabolizing carbohydrates and fats, processes that generate ATP, the primary energy source for muscle contractions.

Calcium and iron are key minerals supporting exercise performance. Calcium is fundamental for muscle contractions and maintaining strong bones, while iron is a critical component of hemoglobin, facilitating oxygen transport to muscles during physical exertion. These micronutrients collectively support the body's increased demands during physical activity.

Although exercise can elevate micronutrient needs, obtaining these nutrients through a balanced and healthy diet typically suffices, making supplementation unnecessary for most athletes. Prioritizing nutrient-rich foods ensures adequate intake to support energy metabolism, muscle function, and overall athletic performance.

Example 1

Sonia's fatigue during exercise, despite consuming enough carbohydrates, may be linked to a deficiency in certain B vitamins. B vitamins do not directly provide energy because they are non-caloric nutrients, meaning they do not contain calories and cannot serve as a direct energy source. Instead, their primary role is to facilitate the metabolism of carbohydrates, which are essential for producing energy in the body.

Carbohydrate metabolism involves breaking down carbohydrates into glucose, which cells use to generate adenosine triphosphate (ATP), the main energy currency. B vitamins act as coenzymes in this metabolic process, helping enzymes convert carbohydrates into usable energy efficiently. Without adequate B vitamins, this metabolic pathway is impaired, leading to reduced energy production and increased fatigue during physical activity.

It is important to note that B vitamins do not directly influence oxygen uptake by the lungs, nor do they release energy themselves. Their critical function lies in supporting enzymatic reactions that metabolize macronutrients, especially carbohydrates, to sustain energy levels during exercise. Therefore, a deficiency in B vitamins can hinder energy metabolism, explaining why Sonia might feel fatigued despite sufficient carbohydrate intake.

What might be a symptom of an active person who does not get enough calcium in their diet?

• A. Muscle cramps.
• B. Fatigue during exercise.
• C. Decreased bone density (and eventually osteoporosis).
• D. All of the above.

Answer: (D)

Here’s what students ask on this topic:

How does physical activity affect macronutrient needs like carbohydrates, proteins, and fats?

Physical activity increases the body's energy and macronutrient needs, especially carbohydrates and proteins. Non-athletes typically require 3-5 grams of carbohydrates and 0.8 grams of protein per kilogram of body weight daily. In contrast, high-performance athletes may need 5-12 grams of carbohydrates and 1.2-2.4 grams of protein per kilogram to support energy demands and muscle repair. Carbohydrates help restore glycogen, the primary energy source during high-intensity exercise, while proteins aid muscle growth and repair. Fat requirements, however, remain consistent at 0.8-1.2 grams per kilogram for both groups, as fats are not the preferred energy source during intense activity and excessive saturated fats can increase disease risk.

What is the recommended timing for meals around exercise to optimize performance and recovery?

Meal timing is crucial for maximizing exercise performance and recovery. It is recommended to consume a meal rich in carbohydrates and proteins about 2-4 hours before exercising to provide energy and support muscle preservation. Eating immediately before exercise is discouraged as a full stomach can impair performance. During exercise lasting longer than one hour, small amounts of simple carbohydrates can be consumed every 15-20 minutes to maintain energy. After exercise, within 30-45 minutes, consuming a meal with a 3:1 carbohydrate to protein ratio helps replenish glycogen stores and promotes muscle recovery. This timing takes advantage of the body's heightened ability to absorb nutrients post-exercise.

Why do physically active individuals have increased micronutrient needs, and which micronutrients are important?

Physically active individuals have slightly increased micronutrient needs due to higher metabolic demands and oxidative stress from exercise. Vitamins E and C are important antioxidants that neutralize free radicals produced during physical activity. B vitamins are essential for metabolizing carbohydrates and fats to produce ATP, the energy currency for muscles. Calcium is vital for muscle contractions and bone health, while iron is crucial for oxygen transport via hemoglobin. Although these needs increase, a balanced diet typically provides sufficient micronutrients, making supplements unnecessary for most active individuals.

How do carbohydrate requirements differ between non-athletes and high-performance athletes?

Carbohydrate requirements vary significantly between non-athletes and high-performance athletes due to differences in energy expenditure. Non-athletes generally need 3-5 grams of carbohydrates per kilogram of body weight daily to meet basic energy needs. High-performance athletes, who engage in intense and prolonged physical activity, require 5-12 grams per kilogram to replenish glycogen stores in muscles, which serve as a critical energy source during high-intensity exercise. This increased intake supports sustained performance and recovery.

What is the significance of the 3:1 carbohydrate to protein ratio in post-exercise meals?

The 3:1 carbohydrate to protein ratio in post-exercise meals is significant because it optimizes glycogen replenishment and muscle recovery. Consuming three parts carbohydrates to one part protein within 30-45 minutes after exercise takes advantage of the body's increased sensitivity to nutrient uptake. Carbohydrates restore depleted glycogen stores, the primary energy reserve in muscles, while proteins provide amino acids necessary for muscle repair and growth. This ratio supports efficient recovery and prepares the body for subsequent physical activity.