I’ve had two periods since starting 5:2. One was a few days early and somewhat lighter than usual (but not dramatically so). I am currently now on the second, and it was a full 9 days early (I’m normally like clockwork) and it’s barely-there. My usual period symptoms of cramps and fatigue were relatively normal with the first period (perhaps a touch milder), but they’re virtually absent this time. It makes me worry about early menopause! (I’m 42.) I’m at a healthy weight (I’ve lost 8 pounds on 5:2, and my BMI is now 20.5).

I’m certainly interested in hearing more about others’ experiences and hearing about what might be going on from a scientific perspective. I’ve been reading such mixed information online. Is this a sign that the fasting is unhealthy for me? It’s unnerving enough that I don’t think I’ll be continuing.

Right now I’m at what I tend to consider my target weight (i.e., if I put on a bit at the holidays, this is the weight I always want to get back to. When the weight started dropping with 5:2, I thought it would be nice to see if I could bring my go lower. But if I’m messing with my hormones–especially if I’m doing something that could trigger menopause!–it’s not worth it since I don’t need to lose weight for health reasons, don’t have a known genetic risk for things like diabetes, and I’m not unhappy with my current weight.

Yes, I too hope this is something the experts are studying. I have gone off the 5:2 for now, and I will see how things go–I might try again if my cycles even out again. Do post again, juliavb, because I’ll be interested to see if your experience continues to be similar.

NorthernGal, I’m 42–but reluctantly turning 43 in June. I’ve had no signs that menopause is approaching (KNOCK ON WOOD!!!) other than the short cycle and EXTREMELY light period. I’m not shy of fats on non-fast days by any means–but I prefer my fat in the form of chocolate, which might not be helpful! Other than that, a fair bit of dairy (cheese, yogurt), eggs, grapeseed oil in salad dressing and cooking. A bit of nuts here and there, but not so much, and I don’t eat meat (I do eat fish, but usually less than once a week).

I was only doing 5:2 for about six weeks, and it seems surprising to me that that would be enough to bring on early menopause. In terms of research on fasting and menopause, I came across one reference to Dutch women in WWII–they were surviving on 500 calories a day for 6 months, and on average went through menopause three months early. So it seems odd that my six weeks with two days at about 300 calories could have such a big impact. On the other hand, perhaps it depends on how close you are to ending your reproductive years–perhaps, for instance, women who experience famine in their teens and twenties experience no changes to menopause, but women who were already closer to menopause accelerate it by several years?

NorthernGal, did what you read about perimenopause suggest that these effects could be reversible, or once that process has been triggered is it a one-way journey?

Hi Hillsy and so sorry not to have replied.

Yes, I think you might be right that it’s different this time, as you’re a little bit older. I’ve come to the conclusion now that fasting is most definitely affecting my cycle and I’ve just missed a period completely. I can’t say I’m happy about it, but I’ve weighed up which is better for me – staying overweight and not affecting my periods, or getting to a healthy weight and potentially having an early menopause. It is most definitely not an easy decision, but I’ve decided that I have to continue with my weight loss for health reasons. Who knows, maybe once I get to my target weight and only fasting once a week for maintenance, my periods will resume as normal.

You’ve probably done your own research, but this is the article that I found which shows the link between fasting and women’s hormones

http://www.precisionnutrition.com/intermittent-fasting-women

HI,thank you all for the threads really helping

I wanted to update in case others are trying to figure this out. I would say that, to my shock and horror, I am definitely in perimenopause, with or without the 5:2. My cycles are decidedly erratic–some long, some short, some normal. (When short, very light flow. When long, normal flow.) I tend to know when I ovulate, and I think the short cycles have been anovulatory.

However, I have been on and off with 5:2, and although I am not quite certain of the pattern, it does seem that in months that I am being more rigourous with fasting, I am less likely to ovulate. I would need to be more precise to be absolutely sure, but it seems that for me, fasting tends to suppress ovulation, but I suspect that that is because my hormones are in flux anyway and perhaps more sensitive than they would have been a decade ago to things like food intake. My hunch is that 5:2 is not causing it, but is accentuating/intensifying it.