BMI and menopause

What's happening to your body

Menopause usually happens somewhere between 45 and 55, and the years of shifting hormones before it, the perimenopause, can start earlier than many women expect. A lot of women notice their jeans fitting differently during this stretch even though nothing about their eating has changed. It isn't in your head, and it isn't a lack of willpower.

Usually a few things are going on at once:

• Falling oestrogen, which changes where your body prefers to store fat.
• Gradual muscle loss, which starts in your 30s but tends to pick up pace (more on this in healthy BMI by age). Less muscle means you burn slightly fewer calories just sitting still.
• Everything else about midlife. Night sweats that wreck your sleep, less energy for exercise, stress from work or caring for children and parents at the same time.

Research that has followed women through their 40s and 50s suggests weight tends to rise steadily with age during this period rather than jumping suddenly at the menopause itself. What does shift noticeably around the menopause is body shape.

Why it tends to go to your middle

Before menopause, oestrogen encourages your body to store fat on your hips and thighs. As levels drop, more fat is stored around your tummy instead, including the deeper visceral fat that surrounds your organs.

So you can weigh exactly the same as you did at 40 and still find your waistbands getting tighter. This matters for more than clothes. Fat around the middle is more closely linked to heart disease and type 2 diabetes, and women's risk of heart disease goes up after the menopause.

Why your BMI might not move at all

BMI only knows your height and weight, which is the main reason it can be inaccurate for women. Imagine losing two kilos of muscle and gaining two kilos of fat around your middle over a few years. Your BMI stays exactly where it was, while the thing that actually affects your health has changed.

That's why this is a good time to start measuring your waist as well. Our guide to waist-to-height ratio shows you how to do it properly. A ratio under 0.5 is the target, and it'll often pick up changes long before the scales do.

Does HRT make you put on weight?

It's one of the most common worries about starting HRT. According to the NHS, there's little evidence that most types of HRT cause weight gain, and weight gain around the menopause can happen whether or not you take it.

If you're weighing up HRT for other symptoms, it's worth talking it through with your GP. Fear of weight gain on its own probably shouldn't be the reason to rule it out.

What actually helps

• Strength work, at least twice a week. The UK Chief Medical Officers recommend muscle-strengthening activity on two or more days a week for all adults. In midlife it's arguably the single most useful thing you can do, because it helps protect both muscle and bone. Weights, resistance bands, Pilates or even heavy gardening all count.
• Protein with each meal. It helps you hold on to muscle and tends to keep you fuller for longer.
• Protecting your sleep. Poor sleep makes hunger harder to manage. If night sweats are keeping you awake, that's a good reason to see your GP.
• Looking at what you drink. Alcohol adds calories without filling you up, and some women find it sets off hot flushes too.
• Resetting your expectations. Weight comes off more slowly than it did at 30. Small changes you can keep up beat crash diets, which also strip away the muscle you're trying to keep.

When to talk to your GP

Book an appointment if menopause symptoms are affecting your day-to-day life, if you'd like support with your weight, or if your weight is changing in a way that doesn't match anything you've changed. An underactive thyroid is fairly common in women in midlife and some of its symptoms, including tiredness and weight gain, overlap with the menopause, so it's worth ruling out.