How the menstrual cycle affects weight loss, hunger and exercise

When we look at calorie deficits and tracking weight loss, it’s easy to forget the role that female hormones play. The menstrual cycle normally occurs over four weeks and is driven by two hormones; Oestrogen and Progesterone. During these four weeks, huge changes happen in the female body, which affects everything from energy levels to hunger, body weight and mood.

In the first two weeks of the cycle, known as the follicular phase, Oestrogen levels rise steadily, until just before ovulation (around day 14), at which point they fall very quickly. Just before Oestrogen levels fall, Progesterone levels start to increase, peaking at around day 21, before gradually dropping away again over the next week. These last two weeks are called the Luteal phase.

These two phases can dramatically impact your eating habits. After ovulation, once you start the Luteal phase, you are going to feel much more hungry and in fact may well eat significantly more than you do in the Follicular phase. You may also have a higher craving for sweet and high-fat foods, such as chocolate, due to increased metabolic demand (your body needs more energy).

Progesterone, which is higher in the Luteal phase, also promotes fat storage, which can not only lead to binge-eating, it’s also going to affect your body weight. Progesterone is also generally considered a depressant, which is why mood can drop after ovulation. Conversely, high levels of Oestrogen in the follicular phase actually leads to decreased appetite, so you will generally feel less hungry and be happier. With Progesterone levels low, fat storage is not promoted and so you may well see more weight loss in this phase.

The levels of hormones and the changes occurring in the uterus, will also affect your energy levels when it comes to exercise. In the first two weeks of the cycle, prior to ovulation, you will generally feel more energised and have more muscle strength. However, in the second two weeks, energy levels can drop and you might feel that you can’t even fight your way out of a wet paper bag!

Women also have testosterone in their bodies, although at lower levels than men. Testosterone is a key hormone in the development of muscle and it is at its highest levels right around ovulation. Combined with high levels of Oestrogen, the days running up to day 14 of the cycle may well be where you have the highest energy, best mood and greatest strength & endurance.

Taking all this into consideration, it’s no surprise that calorie tracking can be much harder for half of the month. In addition, body-weight can change significantly, depending on the phase of they cycle you are in. Rather than weighing weekly and being disappointed when you don’t see changes week in, week out, try weighing at the same point in your cycle. The best time to weigh is probably around day seven, so mid-way between your period and ovulation. At this point water retention and fat storage should be at their lowest levels.

If you’re really struggling with hunger in the Luteal stage, after ovulation, then maybe adjust your calorie tracking to take advantage of the lower appetite before ovulation. For instance, you could lower your calorie intake by 1-200 calories per day for the first two weeks of your cycle, to give yourself those extra calories in the second two weeks, but sticking to your overall calorie allowance over that four-week period.