A.2.2.1 Macronutrients and their role in energy maintenance Notes

Macronutrients and Their Role in Energy Maintenance

1. The three primary macronutrients - carbohydrates, proteins, and lipids- contribute differently to energy metabolism based on factors such as exercise intensity, duration, and an individual's physiological state.
2. They support growth, rest, and physical activity, with each macronutrient playing a unique role.

Carbohydrates: The Body's Preferred Fuel

Carbohydrates serve as the primary fuel source for most bodily functions and physical activities, particularly during high-intensity exercise.

Types of Carbohydrates

1. Monosaccharides

1. The simplest form of carbohydrate, consisting of a single sugar molecule.
2. These are easily absorbed by the body.
3. Examples include glucose, fructose, and galactose.

2. Disaccharides

1. Composed of two monosaccharides linked together.
2. Examples include sucrose (glucose + fructose) and lactose (glucose + galactose).

3. Oligosaccharides

1. These carbohydrates contain 3 to 9 sugar units.
2. An example is maltodextrin, which is often used in processed foods for quick energy release.

4. Polysaccharides

1. Long chains of monosaccharides, such as starch and glycogen, that provide long-lasting energy.
2. These are broken down into glucose during digestion.

Dietary Fiber

1. Some polysaccharides, like cellulose, cannot be digested by the human body and are considered dietary fiber.
2. Though not a direct energy source, fiber is crucial for digestive health.

Metabolic role

1. Digested carbohydrates are broken down into glucose, which enters the bloodstream.
2. Excess glucose is stored in the liver and muscles as glycogen through a process called glycogenesis.
3. During exercise, glycogen is broken down into glucose via glycogenolysis and used for ATP production.

Metabolic Pathways of Carbohydrates

1. In anaerobic metabolism, carbohydrates provide rapid energy without requiring oxygen (e.g., during sprinting).
2. In aerobic metabolism, glucose is oxidized efficiently to produce ATP for prolonged exercise.

Lipids: Energy Storage and More

1. Lipids, commonly known as fats, are the body's most energy-dense macronutrient, providing a long-term energy reserve.
2. Fats are used predominantly during low-to-moderate-intensity exercise, especially when exercise duration is long.

Types of Lipids

1. Triglycerides: These are the most common form of fat in the body, composed of one glycerol molecule and three fatty acids. Triglycerides serve as a major energy storage molecule.
2. Phospholipids: These are major components of cell membranes and are made up of two fatty acids and a phosphate group. They are crucial for maintaining cell structure and function.
3. Sterols: Sterols, like cholesterol, are important for producing hormones and maintaining cell membrane integrity.

Fatty Acid Classifications

1. Saturated Fatty Acids (SFA)

1. These have the maximum number of hydrogen atoms attached to each carbon atom, making them solid at room temperature.
2. Commonly found in animal products.

2. Unsaturated Fatty Acids

1. These fats have one or more double bonds between carbon atoms, making them liquid at room temperature.
2. Unsaturated fats can be further classified into:
   1. Monounsaturated Fatty Acids (MUFA): Contain one double bond, found in foods like olive oil.
   2. Polyunsaturated Fatty Acids (PUFA): Contain multiple double bonds, with examples like omega-3 and omega-6 fatty acids.

Metabolic Role

1. Stored as triglycerides in adipose tissue and muscle.
2. Broken down through lipolysis into glycerol and free fatty acids (FFAs).
3. FFAs enter the bloodstream and undergo beta-oxidation to generate ATP in mitochondria.

Energy Contribution

1. Dominant fuel source during rest and low-intensity activities (e.g., walking, yoga).
2. Contributes more energy as exercise duration increases and glycogen stores decrease.
3. Requires oxygen to be metabolized, making it inefficient for high-intensity activity.

Proteins as an Energy Source

1. Proteins primarily serve a structural and functional role in the body but can be used for energy when carbohydrate and fat stores are low.
2. Amino Acids are the building blocks of proteins.
3. There are 20 standard amino acids, which combine in various sequences to form proteins.

Essential vs Non-Essential Amino Acids

1. Essential amino acids are those that the body cannot synthesize and must be obtained from food (e.g., valine, leucine, lysine).
2. Non-essential amino acids are those that the body can produce on its own (e.g., alanine, asparagine, glutamine).

Metabolic Role

1. Proteins are made of amino acids, which are used for muscle repair, enzyme production, and immune function.
2. Under normal conditions, proteins contribute less than 5% of total energy production.
3. During prolonged exercise or starvation, proteins undergo gluconeogenesis, where amino acids are converted into glucose in the liver.

Energy Contribution

1. Low contribution during short-term exercise.
2. Becomes more significant in prolonged endurance exercise (e.g., ultra-marathons).
3. BCAAs (branched-chain amino acids such as leucine, isoleucine, valine) can be directly oxidized by muscles for ATP production.

Factors Influencing Macronutrient Contributions

The contribution of macronutrients to energy production is not static. It varies based on individual factors, including body composition, age, sex, and activity level.

Body Composition

1. Muscle Mass: Individuals with a higher muscle mass will have higher energy demands and rely more on carbohydrates and proteins to fuel muscles.
2. Fat Mass: Individuals with a higher body fat percentage tend to rely on lipids for energy during endurance exercise because the body can utilize fat stores more efficiently.

Age & Sex Differences

1. Metabolic Rate: Younger individuals tend to have a higher metabolic rate, which means they require more energy and consequently consume more carbohydrates and proteins to meet these needs.
2. Hormonal Influence:
   1. Men tend to have more muscle mass and higher testosterone levels, which support a higher reliance on carbohydrates for energy in high-intensity sports.
   2. Women generally have a higher percentage of body fat, which allows for more efficient use of lipids during endurance activities.

Activity Level & Exercise Type

Nutrition Strategies

Pre-Exercise Nutrition Strategies

1. Pre-exercise nutrition plays a critical role in enhancing performance during both endurance and high-intensity activities.
2. Proper fueling before exercise helps optimize energy availability, delay fatigue, and enhance recovery.

Carbohydrate Loading

1. Carbohydrate loading enhances endurance performance by ensuring sufficient energy is available for prolonged physical activity.
2. Glycogen is stored in muscles and liver and is the primary fuel used during aerobic activity.
3. By carbohydrate loading, athletes can increase their glycogen stores beyond normal levels.
4. A well-conducted loading protocol ensures a maximal glycogen reserve, helping prevent early fatigue and maintaining energy levels throughout the event.

Phases of Carbohydrate Loading

1. Depletion Phase: Involves a reduction in carbohydrate intake and intense exercise (usually about 3-4 days before the event) to deplete glycogen stores.
2. Loading Phase: The last 3-4 days before the event involve a high-carbohydrate diet (up to 10-12g per kg of body weight) combined with rest to allow for supercompensation of glycogen stores.

Timing and Composition

1. The timing and composition of your pre-exercise meal can affect energy levels, glycogen availability, and overall performance.
2. The type of carbohydrate (low vs. high GI) you consume can also have different effects on energy release during exercise.

Low Glycemic Index (GI) vs. High Glycemic Index (GI) Carbs

1. Low-GI Carbohydrates (e.g., whole grains, fruits) are digested more slowly and provide a steady release of glucose, helping to sustain energy levels during prolonged exercise.
2. High-GI Carbohydrates (e.g., white bread, potatoes, sugary foods) are rapidly digested and cause a quick spike in blood glucose and insulin, providing immediate energy for short bursts of intense exercise.

Timing

1. Ideally, a pre-exercise meal should be consumed 2-3 hours before exercise to allow time for digestion.
2. A meal high in carbohydrates, moderate in protein, and low in fat helps provide adequate fuel without causing digestive discomfort.
3. If eating closer to exercise (30 minutes to 1 hour), focus on high-GI carbohydrates for a quick energy boost.

Protein Intake

1. While carbohydrates are the primary source of energy during exercise, protein plays a crucial role in muscle repair and growth.
2. Consuming protein before a workout can also have benefits for muscle performance and recovery.

Role of Protein in Pre-Exercise Nutrition:

1. Pre-exercise protein intake helps ensure that amino acids are available for muscle repair and reduces muscle breakdown during prolonged or high-intensity activities.
2. While protein is not the primary fuel source during exercise, it helps to reduce muscle damage and accelerate recovery post-exercise.

Nutrition During Exercise

1. During exercise, the body’s nutritional needs shift. It is essential to focus on hydration, electrolyte replenishment, and carbohydrate replenishment to maintain performance, endurance, and recovery.
2. Proper hydration is vital for maintaining plasma volume, regulating body temperature, and sustaining exercise performance.
3. Electrolytes, like sodium, potassium, and chloride, play a crucial role in maintaining fluid balance and ensuring proper muscle function.

Hydration During Exercise

1. Fluid loss during exercise (due to sweating) can result in dehydration, leading to reduced performance, muscle cramping, heat exhaustion, and fatigue.
2. Sweating leads to the loss of not only water but also important electrolytes, which must be replaced to avoid hyponatremia (low sodium levels in the blood).

Electrolyte Replacement

1. Replacing electrolytes is essential for maintaining nerve function, muscle contractions, and hydration balance.
2. Sports drinks containing sodium, potassium, and other electrolytes are recommended for exercise durations longer than 1 hour to ensure proper hydration and to prevent cramping.

Carbohydrate Replenishment

1. Carbohydrate replenishment is crucial for maintaining blood glucose levels and ensuring continued energy during exercise, especially in endurance sports.
2. Since muscle glycogen stores deplete after 60-90 minutes of intense exercise, consuming carbohydrates during exercise helps maintain performance and delay fatigue.

Carbohydrate Strategies During Exercise

1. Sports drinks, glucose gels, and energy bars are commonly used for carbohydrate replenishment during exercise.
2. The goal is to consume 30-60g of carbohydrates per hour during exercise lasting longer than 1 hour to maintain blood glucose levels and delay glycogen depletion.

Effectiveness

1. Studies show that consuming carbohydrates during endurance events can improve performance by preventing hypoglycemia and improving fatigue resistance.
2. Consuming carbohydrates in the form of glucose or fructose (or a combination of both) helps maximize absorption rates.

LEA & RED-S

Low Energy Availability (LEA)

1. LEA occurs when an individual’s caloric intake is insufficient to meet the energy demands required for bodily functions, including daily activities and exercise.
2. LEA can be caused by several factors such as inadequate nutrition, high physical activity levels without compensating caloric intake, or an imbalance in energy expenditure and intake.
3. If energy availability is consistently low, it leads to a state where the body lacks the necessary energy to perform essential physiological functions, affecting overall health and performance.

Relative Energy Deficiency in Sport (RED-S)

1. RED-S is a condition that occurs as a result of prolonged LEA and is commonly seen in athletes.
2. It negatively impacts various physiological systems, particularly hormonal balance, bone health, and performance.
3. RED-S differs from LEA in that RED-S reflects a chronic, more severe condition that has far-reaching consequences, impacting several systems in the body.
4. It is typically seen in sports requiring low body weight or high endurance, such as gymnastics, long-distance running, and figure skating.
5. It can also occur in athletes under extreme pressure to lose weight or maintain a specific body composition.

Consequences of RED-S

1. Hormonal imbalances and disruptions in reproductive and metabolic hormones.
2. Reduced bone health, increasing susceptibility to stress fractures and decreased bone density.
3. Impaired performance due to reduced recovery capacity, fatigue, and slower adaptation to training.

Effects of LEA & RED-S

1. Decreased Bone Density

1. One of the most significant long-term consequences of RED-S is the reduction in bone density.
2. Low energy availability disrupts the body's ability to regulate bone resorption and formation, making bones more fragile and increasing the risk of stress fractures.
3. Insufficient caloric intake leads to lower levels of estrogen (in females) and testosterone (in males), both of which play a crucial role in maintaining bone health.

Hormonal Imbalances

1. LEA and RED-S cause disruptions in several key hormones, particularly those involved in metabolism and reproduction.
2. In women, this can lead to menstrual dysfunction, such as amenorrhea (absence of menstruation), while in men, low testosterone levels may occur.
3. These hormonal imbalances impact not just reproductive health, but also metabolic functions, mood regulation, and overall health.

Reduced Performance

1. The primary concern for athletes with LEA or RED-S is reduced performance.
2. The body does not have the necessary energy to fuel exercise and recovery, leading to fatigue, decreased endurance, slower reaction times, and impaired recovery.
3. Athletes may struggle to complete workouts at the required intensity, experience delayed recovery, and have an increased risk of injury due to the body's compromised ability to repair tissues.