There was a great deal of attention given to the question how many calories do you burn on your period in the scientific community of the 1920s. Many studies were conducted and almost an equal number of conflicting results were published. It seemed almost as if there would never be a consensus as to how many extra calories you burn on you burn on your period.
Finally, towards the beginning of the 1930s, a conclusive study by Gustafson and Benedict revealed some strong data, which shed light on the question of how many calories you burn while on your period. These findings showed that there is a significant and predictable lowering of the basal metabolic rate of menstruating women. This result was within experimental limits of error, such as the psychological and emotional state of the women, the time of year and other external factors such as temperature and humidity.
The basal metabolic rate of an average woman is around 1500 kcal per day. If we assume that the study above found a 10% decrease in metabolic rate, this would mean that women burn about 150 calories less per day whilst on their period. If we further assume that a woman’s period lasts for an average of 5 days, this means that she will burn a total of 750 calories less over the course of her menstrual cycle.
There is another effect during menstruation with respect to calorie consumption that does not seem to be mentioned in the literature above. This is the fact that women will lose a certain amount of blood and bodily liquid on their period. This must then be compensated for by the body, which of course requires energy. This effect will counteract that of the decrease in basal metabolic rate.