What is perimenopause, and when does it start?

What changes in perimenopause?

Perimenopause rarely starts with a bang. The classic first sign is a cycle that changes length: under the STRAW+10 staging criteria, the early transition is a difference of 7 days or more between consecutive cycles, and the late transition is 60 or more days without a period. Nobody hands us the full list of what else shifts, so here it is, with what the research shows for each part.

How long it lasts is harder to answer, because menstrual stage is an imprecise predictor of when the final period will happen, so nobody can tell you exactly how long yours will be. What the research can measure is symptoms: in SWAN, frequent vasomotor symptoms lasted a median of about 7.4 years in total and about 4.5 years after the final period. That is the length of the symptoms, not of the stage itself.

Beyond the calendar, the body shifts too. In SWAN, lean mass falls and the rate of fat gain roughly doubles at the start of the transition, while total weight does not accelerate, and these changes level off about 2 years after the final period. That is a pattern, not a personal failing.

Muscle. Muscle mass and power decline, and many women find the same meals and workouts get them less than they used to. The term is anabolic resistance: muscle responds less to protein and training. It isn't you slacking, it's physiology, and how much protein do I need covers the numbers by body weight.

Belly fat. Fat tends to move to the abdomen during the transition, even when the scale stays put, which is why your waistband can tighten while the number doesn't. HIIT and strength training both help with visceral fat, and a tape measure at the waist is a simple home check. Under 31.5 in (80 cm) is the target we use here: a check, not a verdict, and it says nothing about your worth. Food matters too, and high fiber foods is a friendly place to start, with strength training for women for the training side.

Bone. The hormonal backdrop is estrogen, which falls across the transition, and bone feels it. In SWAN, lumbar spine density fell 10.6% over 10 years, and 7.38 percentage points of that fell in the transmenopause, the window from about a year before to 2 years after the final period. At the femoral neck it was 5.8 of 9.1. You can't feel it happening, which is exactly why it gets ignored.

Heart and metabolism. Cholesterol, blood sugar and blood pressure are worth checking regularly through these years, and many women find the transition a sensible moment to book those appointments.

Sleep, mood and brain. Night sweats and early waking become common, alongside hot flashes (hot flushes in the UK) in the daytime. Some women also notice low mood, anxiety or brain fog. If you've walked into a room and forgotten why, you're in lovely company, and it's fair to raise it with your doctor (your GP in the UK).

Iron and pelvic floor. Heavy or irregular bleeding can drain your iron stores, so it's worth asking for a ferritin check. Vaginal dryness, urinary urgency and leakage also become more common. Women put up with both for far too long, mainly because nobody asks. Pelvic floor training and local treatment are real options for the second, and a simple blood test is the start for the first.

If changes like these turn up well before your 40s, the page on early menopause is for you and explains what to ask your doctor.

What helps most, based on the evidence?

Lifting heavy comes first and protein a very close second, with short HIIT, sleep and regular checks right behind. Together they work on muscle, bone and belly fat at the same time, which is why I'd start there before looking at anything more exotic.

Protein. Spreading it across the day matters because muscle responds less than it used to, so one big dinner doesn't do the job of several decent meals. Breakfast is where I'd look first. Toast on its own won't get you there, and most of us are surprised when we actually add it up.

Lift heavy. In my view this is the most effective single habit on the list, because it works on muscle and bone together. The LIFTMOR trial found that heavy resistance and impact training improved bone density in postmenopausal women, which is why heavy and impact loading sit alongside calcium and vitamin D for the years of fastest loss. Strong and lean is a lovely goal: the kind of strength that carries you through your day, not a number on a scale.

Short HIIT. A meta-analysis found HIIT reduces abdominal and visceral fat. It sits beside lifting, not in place of it, and short is the point. If your joints or your week can't take it right now, lifting and walking still do a great deal.

Sleep and alcohol. A steady sleep routine and a cool room help with night sweats and early waking, and many women find that drinking less helps both sleep and belly fat. Not the fun answer, but it costs nothing to try.

Treatment. Lifestyle isn't the whole story, and nobody gets a medal for putting up with symptoms. Ask your doctor (your GP in the UK) about night sweats, low mood, anxiety, brain fog and vaginal or urinary symptoms. HRT is one option worth discussing, and The Menopause Society's 2022 position statement is a useful US reference. Whether it fits depends on your symptoms, your history and your preferences. Natural-first is a fair approach too, as long as you know when a remedy has little evidence behind it and you don't delay a treatment that works.

Checks. These are small, boring appointments that pay off later: cholesterol, blood sugar and blood pressure, plus ferritin if your bleeding is heavy or irregular. They're easier to book when you've written your questions down beforehand.

If you only have time for one change, mine would be lifting, with protein close behind. That's my opinion from reading the evidence, and what suits your week, your joints and your starting point will differ. Trial and error is allowed. Be kind to yourself while you work it out!

Next steps

So, where to start? Pick one thing this week, not all of them. Measure your waist and write it down, add up your protein for one ordinary day against the range above, or book your first heavy lifting session and add short HIIT once that feels settled. Many women find a short list of questions makes appointments easier: ask your doctor (your GP in the UK) for checks of cholesterol, blood sugar and blood pressure, plus ferritin if your bleeding is heavy or irregular, and raise any symptom that is wearing you down. If anything on the red flag list applies, please see your doctor promptly instead of waiting for it to settle. Not sure this is even your stage yet? The which stage am I in tool takes you through it. From here, the pages on symptoms, nutrition, training, sleep and health checks go deeper on each part. I've given you what the research shows and what I'd choose first, but your body, your history and your week are yours. Take what fits, leave what doesn't, and adjust as you go: this is not one size fits all.