Final answer:
Intermittent fasting is a nutritionally productive alternative to caloric restriction, involving cycles of fasting and eating without specifying food types. Option b is the correct answer.
Step-by-step explanation:
A nutritionally productive potential alternative to caloric restriction (CR) appears to be intermittent fasting. In contrast to continuous caloric restriction, intermittent fasting involves cycles of fasting and eating. During fasting phases, metabolic changes occur similar to those in prolonged fasting, such as using fat reserves for energy after glycogen stores are depleted, though generally not to the extent of starvation conditions. It avoids the extreme of undernutrition, focusing instead on timing food intake to allow the body periods of low energy intake.
While both fasting and intermittent fasting lead to metabolic adjustments, intermittent fasting avoids the negative effects of starvation, including the breakdown of protein after fat reserves are used up. Unlike a high-protein diet or a low-carbohydrate diet, intermittent fasting doesn't specify what types of foods are consumed, focusing instead on when food is consumed. This can make it a more sustainable option than fad diets that promise rapid weight loss, target specific body parts, or do not require exercise.