By Melissa Bosslet, RD, LN, CPT
I've been asked this question on more than one occasion lately, so I thought I would take the time to address the subject. The simple answer is no, metabolic rate and calorie expenditure do not increase during that time of the month. What does happen is a change in hormones that cause an increase in appetite.
Here's what happens - on Day 1 of your cycle, the follicular phase begins. Estrogen increases and progesterone decreases. After 13 days, generally the beginning of your period, luteinizing hormone and follicular stimulating hormones both increase, stimulating ovulation. The Luteal Phase begins and if the eggs are not fertilized, the uterus sheds its lining. There is a decrease in both progesterone and estrogen at this time.
Immediately before menstruation, there is a surge in progesterone. A high progesterone to estrogen ratio is responsible for an increase in food cravings, fluid retention, mood swings, and other PMS symptoms. High progesterone also causes relaxation of smooth muscle tissue, such as in the uterus and bowels. Relaxation of the bowels leads to expansion, thus the bloated feeling in the gut. These actions are all necessary to prepare the woman's body for pregnancy and to increase weight. If the female does not get pregnant, then there is really no need for more food.
Check the blog tomorrow for tips on how to reduce bloating, PMS, and prevent the mid-month weight gain.
Source: Hormonal Balance: Understanding Hormones, Weight, and Your Metabolism by Scott Isaacs, MD, FACP, FACE