In recent years, much work has been done regarding basal metabolism and researches on this field have come up with the development of BMR standards. However, there is still a paucity of studies on the effect of minor influences on BMR such as the preceding day's intake. It's cumulative effect over long periods may be an important determinant in differences in daily energy expenditure and if large enough may warrant consideration when defining energy requirements of individuals or population groups. This study attempts to determine the effect on basal metabolic rate of the preceding day's intake. Results of this study may be able to at least add to existing knowledge in the extent of short-term fluctuations in energy intake and which may possibly serve as background information to other studies. In this paper are presented some early and recent findings/investigations related to the topic, methods of measurements and how the study was conducted. The study covered a total of 30 normal women, resident within the Glasgow area, aged 21 to 43 years, and who qualified based on certain criteria set. These included post-doctoral and senior honours students and staff of the Physiology department and some post-graduate students from other departments of the University of Glasgow. Basal metabolic rate was assessed using the Douglas Bag technique a day after differing levels of energy intake were consumed. Subjects were interviewed on their actual daily energy intake from which a menu was planned for each of the 3 phases of the study. These phases included; the Initial phase, where a day prior to the BMR measurement, energy intake was not controlled - the subject following her normal daily eating habit; the Standard Diet phase, where a day prior to the measurement, the energy consumed was calculated as the requirement of each particular subject based on the measured BMR times 1.4; the Overeating or "40% more" phase, where the diet consumed was 40% more than the average computed from the Standard Diet phase; and the Undereating or "40% less" phase, where the diet plan was based on a deficit of 40% computed from the average intake in the Standard Diet phase. Results of the study showed no significant changes in the basal metabolic rate in all phases of the experiment. Under conditions of these experiments, the study indicated that the post-absorptive BMR did not show substantial variations on differing levels of intake measured a day after.