Final answer:
Metabolic slowing is the biological explanation that best accounts for why many people regain weight after losing it. After weight loss, the body's metabolic rate can slow down, leading to easier weight regain. Hormonal factors like leptin resistance also contribute by making individuals feel less satiated.
Step-by-step explanation:
Biological Explanation for Regaining Weight After Losing It Many people struggle with weight regain after successful weight loss. The biological explanation that best describes why this happens is metabolic slowing (A). After weight loss, the body's metabolic rate often slows down as an adaptive response, burning fewer calories at rest. This metabolic adaptation makes it easier to regain weight, even when a person is not eating excessively. Moreover, literature shows that there are no significant changes in metabolic rate between individuals who had recently lost weight and a control group, suggesting that other factors, such as social and environmental influences, also play a crucial role in the regulation of body weight. Leptin resistance is another factor linked to challenges in maintaining weight loss. Leptin, the satiety hormone, can become less effective in signaling fullness in individuals who are obese. Consequently, a person might experience increased hunger (B) and continue to eat beyond their caloric needs, promoting weight regain. However, while hormonal imbalances like leptin resistance may contribute to increased hunger, it is metabolic slowing that directly influences the body's energy expenditure, providing a more applicable answer to the question. Additionally, the set-point theory, which is often referenced to explain body weight regulation, fails to adequately accommodate the complexity of obesity and the various factors that contribute to weight gain.