When individuals lose weight quickly, most of the weight lost is from:

• A. loss of adipose tissue
• B. loss of bone mass
• C. loss of muscle protein
• D. water loss

Answer: (D)

Verified step by step guidance

1. Understand the context: Rapid weight loss often involves changes in the body's water balance, fat stores, muscle mass, and bone density. The question asks us to identify the primary source of weight loss during quick weight reduction.
2. Recall the biological principle: The body stores water in association with glycogen in the liver and muscles. When individuals reduce calorie intake or engage in rapid weight loss methods, glycogen stores are depleted, and the water associated with glycogen is released, leading to water loss.
3. Eliminate incorrect options: Loss of adipose tissue (fat) occurs more gradually because fat metabolism requires sustained caloric deficits over time. Loss of bone mass is not a significant factor in short-term weight loss. Loss of muscle protein can occur but is not the primary contributor to rapid weight loss.
4. Focus on the correct answer: Water loss is the most significant contributor to rapid weight loss because it is associated with glycogen depletion and changes in hydration levels.
5. Conclude: The correct answer is water loss, as it is the most immediate and substantial factor in quick weight reduction, compared to the slower processes of fat or muscle breakdown.