Refeeding Syndrome, Exercise Physiology, and Carbohydrate Loading: Key Concepts for Nutrition and Metabolism

What is Refeeding Syndrome?

Abnormal metabolism resulting from a shift from fat to carbohydrates as a substrate when a person is aggressively fed after a period of starvation.

Who is at risk for Refeeding Syndrome?

Individuals who are severely malnourished, anorexics, or morbidly obese after massive weight loss.

What are common symptoms of Refeeding Syndrome?

Myocardial dysfunction, tachycardia, hypotension, respiratory failure, edema, dizziness, and muscle weakness.

What hormonal changes occur during starvation?

The body uses fat for energy and glucagon is the predominant hormone.

What happens to insulin levels when refeeding begins?

Insulin levels increase to cover carbohydrate influx while glucagon levels decrease.

What electrolytes are affected during Refeeding Syndrome?

Phosphorus, potassium, and magnesium levels decrease as they are driven into cells.

What is the initial treatment for Refeeding Syndrome?

Restrict carbohydrates initially and gradually increase them, increase protein intake, maintain fluid balance, and monitor electrolyte values.

Define exercise in the context of nutrition.

Planned, structured physical activity to enhance physical fitness.

How does exercise affect hormone levels?

Exercise increases circulating levels of epinephrine, cortisol, and growth hormone.

What are the three energy systems that supply ATP during exercise?

The ATP-phosphocreatine system, the lactic acid system, and the oxidative system.

What is the ATP-phosphocreatine system?

An energy system that provides ATP for high-intensity, short-duration activities like weightlifting and sprinting.

How long does the ATP-phosphocreatine system last?

It diminishes after the first 15-25 seconds of strenuous exercise.

What is the primary function of the lactic acid system?

To generate ATP quickly for high-intensity exercise lasting from about 20 to 75 seconds.

What happens when lactate production exceeds clearance?

Blood lactate increases, lowering the pH of blood.

What is the oxidative system?

An energy system that involves the TCA Cycle and oxidative phosphorylation, providing energy for prolonged exercise.

What type of exercise predominantly uses the oxidative system?

Exercise lasting longer than 2 or 3 minutes, such as distance running or swimming.

What fuel sources does skeletal muscle primarily use during light physical activity?

Fatty acids.

What causes muscle fatigue during exercise?

Inadequate supply of glucose.

What is carbohydrate loading?

A regimen to maximize glycogen stores before endurance events, involving a mix of low and high carbohydrate diets.

What are the two regimens for carbohydrate loading?

Classical regimen and modified regimen.

What is the classical regimen for carbohydrate loading?

Two sessions of intense exercise, followed by 2 days of low-CHO diet, then 3 days of high-CHO diet and rest.

What is the modified regimen for carbohydrate loading?

Exercise tapered over 5 days, 1 day of rest, followed by 3 days of 50%-CHO diet and then 3 days of 70%-CHO diet.