Whether a person burns more calories while on their period is complex, but the answer is generally yes, though the increase does not occur precisely during the bleeding phase. Energy expenditure shifts throughout the menstrual cycle due to hormonal changes that directly influence metabolism. The baseline energy burned at rest, known as the Resting Metabolic Rate (RMR), is the main factor that fluctuates. This hormonal relationship creates a subtle but measurable difference in how the body uses energy across the cycle.
Hormonal Drivers of Metabolic Rate Changes
The primary driver of metabolic changes is the hormone progesterone, which rises significantly after ovulation. Progesterone has a thermogenic effect, increasing heat production and causing a measurable rise in the Basal Body Temperature (BBT). The body expends more energy to sustain this slightly elevated temperature, which boosts the overall Resting Metabolic Rate (RMR). This metabolic increase results from the body working harder to maintain basic functions at a higher thermal set point. In contrast, estrogen, the dominant hormone during the first half of the cycle, tends to keep RMR stable or slightly lower.
Quantifying Calorie Burn Across the Cycle Phases
The menstrual cycle is divided into the follicular phase and the luteal phase. The follicular phase, from the start of the period until ovulation, is characterized by lower hormone levels and a stable RMR. The true increase in calorie burn occurs during the luteal phase, which begins after ovulation. Research shows a significant increase in RMR during the luteal phase, averaging a 5% to 10% rise for most individuals. This translates to burning approximately 100 to 300 extra calories per day, with the highest output observed in the last 7 to 10 days before menstruation when progesterone levels peak.
Practical Significance for Daily Energy Expenditure
While RMR increases during the luteal phase, the Total Daily Energy Expenditure (TDEE) is also affected by physical activity and digestion. This RMR increase is often counterbalanced by changes in appetite and activity levels. Many people experience increased appetite and cravings during the luteal phase, often for calorie-dense foods. Studies suggest this increased energy intake can average around 168 calories per day, potentially offsetting the RMR increase. Consequently, the net energy balance often remains close to neutral, meaning this small metabolic fluctuation does not necessitate major caloric adjustments for weight management.