During Caloric Restriction between 1957 and 1963, the dominant paradigm coalesced around the energetics of nutrient limitation, revealing cross-species metabolic adaptations as a coherent framework. Researchers emphasized whole-body energy expenditure, organ-level calorigenesis, and endocrine/electrolyte adjustments accompanying fasting and restricted intake, employing methods such as formula diets and time-limited feeding to map weight trajectories and metabolic responses. Genetic and adipose-tissue studies began linking fat distribution and tissue metabolism to caloric restriction, while macronutrient composition and energy-source availability modulated outcomes, including endocrine regulation and electrolyte balance. Historical Significance: These early works established energy balance as a dynamic regulatory system and provided foundational methods for quantifying the caloric costs of weight change. The Caloric Equivalents of Gained or Lost Weight introduced a practical framework for linking weight shifts to energy flux, while Appetite and the Relationships between Expenditure and Intake of Calories in Man highlighted hunger dynamics and long-term weight regulation. Together with studies on antecedent feeding patterns influencing hepatic lipogenesis and fat depletion after thermal trauma, and the recognition that electrolyte handling modulates fasting outcomes, these papers solidified caloric restriction research as a central paradigm and a basis for future energy-balance investigations.