Are you sure the irregular periods aren't simply due to the stress of changing your diet and losing weight? I'm perimenopausal but I had a hysterectomy a few years ago. I still have my ovaries. I do not know what my period is doing anymore. I haven't really noticed any change to indicate that menopause is on its way. I did get a lot of hot flashes at first on this diet but I honestly believe it was due to giving my body nutrients it had been starved for and having it respond with a flash of hotness. These hot flashes were similar to the hot flashes I got after my hysterectomy. My post-surgery hot flashes went away after a few weeks. I think the stress of surgery caused them. I at first got hot flashes just eating sweet potatoes. Then I would get them from other things like certain supplements that were new. They've subsided and I don't get them anymore. It could just be stress and I wouldn't try to force anything until there are symptoms that are causing serious quality of life issues.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
I can squat 180lbs, press 72.5lbs and deadlift 185lbs