It sneaks up on you. You feel like your normal self and then, one day, you notice that your body shape has changed or that you’re holding on to a few extra pounds. Your body just doesn’t feel the same.

It’s not all in your head. As you get older, there are real changes in your body — some due to age, some due to menopause — that can lead to weight gain. But most women aren’t aware of them.

So, here’s what’s really going on with your body after 40 and what you can do to feel healthy and strong as you age.

The biggest culprit behind your body’s changes after 40? Hormones. These are the chemical messengers that control most body functions, from reproduction to hunger.

As you approach menopause, levels of estrogen, progesterone, and testosterone fluctuate, says Alyssa Dweck, MD, gynecologist and assistant clinical professor at the Mount Sinai School of Medicine.

This fluctuation in hormones causes a cascade of changes, from decreased bone density and lean muscle mass to lower sex drive and mood changes.

The fix: Don’t feel resigned to grinning and bearing the hormonal fluctuations! Talk to friends or family members, or find an online group. “You’ll probably hear that you’re all going through something similar.

When women hear positive stories and that this phase will end, it’s helpful,” says Amanda Thebe, a certified personal trainer and health coach who runs the Facebook group Menopausing So Hard.

Yes, you can blame your hormones for this, too. Not only does your resting metabolic rate naturally slow with age, lower estrogen levels contribute to a sluggish metabolism.

You also start to accumulate more fat, especially around your waistline, says registered dietitian Melissa Burton.

Researchers have found that hormonal changes caused by perimenopause and menopause contribute to changes in body composition, fat accumulation, and fat distribution.

The fix: The best way to keep your metabolism humming? Stay active.

Vera Trifunovich, a personal trainer and wellness coach at Uplift Studios, recommends a combination of strength training and cardiovascular exercise — something with a little impact, like cardio dance or a boxing class.

Plus, eat your fiber. While the average American eats 10 grams of fiber a day, you need between 25 and 35 grams, Burton says. Just make sure you drink plenty of water!

After the age of 40, you lose muscle mass — the main calorie-burning engine in your body — to the tune of 1 percent a year, Burton says. It’s linked to dropping estrogen and testosterone levels that accompanies perimenopause and menopause, says Dweck.

Coupled with a slower metabolism, you don’t burn calories the same way as you did when you were young.

The fix: Strength train or lift weights two to four times a week, Thebe recommends. (No, you won’t bulk up.)

Not only will resistance training rebuild lean muscle mass, which also helps burn fat and rev your metabolism, it helps keep your bones and body strong and healthy.

“Muscle is a necessary requirement to help support your bone structure, supporting your joints and ensuring you have adequate range of motion,” Thebe says.

If you’re new to strength training, consider working with a personal trainer for two to three sessions.

“They can develop a program that is safe for you but will also have an impact on your fitness,” Trifunovich says. Focus on multi-joint exercises that work your full body.

Try Thebe’s workout below. Do each exercise for 30 seconds, and rest for 30 seconds between each exercise. Repeat 4 to 6 times.

Thebe’s workout plan

  • goblet squat
  • kettlebell swing
  • pushup
  • row
  • mountain climbers
  • skater jumps
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As you get older, and especially as you gain weight, the body starts to ignore insulin — the hormone responsible for regulating blood sugar levels.

As a result, you blood sugar is higher, because your cells aren’t absorbing it, says Burton. The result: It feels like you’re hungry, and you may experience more cravings.

Not only can this lead to unwanted pounds, it also puts you at greater risk for type 2 diabetes.

The fix: To avoid a glucose overload, Burton recommends including a mix of carbohydrates, protein, and fat at every meal.

Don’t just load up on carbs. “Protein and healthy fat help the body feel more satisfied for a longer period of time, and you don’t crave those super starchy carbs that can give you a sugar crash,” she says.

Pay attention to where your carbs come from, too. “If you drink juice, it increases blood sugar circulating in the body quickly,” Burton says. “If you eat whole grains, it has more fiber and breaks down slowly,” she says. It gradually releases sugar into the bloodstream.

Dweck suggests really sticking to a Mediterranean-style diet in your 40s. “It’s been shown to be protective against cancer and heart disease, and it doesn’t cause huge swings in blood glucose levels,” she says.

Hormones like ghrelin (which tells you when you’re hungry) and leptin (which tells you when you’re full) also fluctuate.

“As we age, the receptors for these hormones don’t work as well as they used to, and we become resistant to them, too,” Burton says. “It’s not just in your head. You’re actually hungry because of your hormones.”

The fix: Dweck suggests keeping a food diary to pinpoint pitfalls in your eating habits and to get a better handle on your hunger cues. “When you actually write down what you eat, you can see if you’re actually snacking all day or if you’re eating bigger portions,” she says.

A food diary can also tell you if you’re eating enough protein. Burton recommends 20 to 30 grams of protein at each meal, since your body can absorb only so much protein in one sitting.

Between your career, family, and friends in your 40s, exercise can fall further down the priority list. Trifunovich says creaky, achy joints are another reason many women become less active.

“Overuse and joint injuries resulting from all the years of exercise may cause you to give up your favorite activity or force you to slow down,” she says. This can contribute to feeling out of shape.

The fix: Just keep moving. You don’t have to spend hours at the gym or running — find something you love. You’re more likely to stick with it, Trifunovich says.

If injury keeps you from doing your beloved activity, try a new class or at-home workout. (There are tons of streaming workout options available!)

Staying active won’t only enhance your metabolism. The endorphins released during exercise will also boost your mood, Thebe says, and help you feel better in your own skin.

Plus, regular exercise reduces your risk for chronic health conditions, like cardiovascular disease and diabetes.

Women experience a wide variety of stress in middle age, from managing their career and finances while oftentimes caring for both their children and parents.

Researchers have found that black women in particular bear a heavy stress load.

When you’re stressed, your body secretes cortisol, aka the fight-or-flight hormone. “Constant cortisol secretion can cause blood sugar levels to drop, which makes you want to eat more, especially sugar.

You develop fat around the belly,” Dweck says. A larger waistline is linked to conditions like diabetes and heart disease.

The fix: Get a handle on your stress, Dweck says. Whether that’s yoga, meditation, coloring, or reading, find strategies that work for you.

Many women report difficulty sleeping as they get older. Or, maybe you just don’t feel rested, even after a full night’s sleep, which means you have less energy to exercise or be active.

Two of the biggest sleep disruptors at this age are hot flashes and night sweats. You can thank your shifting hormones for that, too.

The fix: First things first: Establish a soothing bedtime routine. In particular, reduce your use of electronics before going to sleep, Dweck says.

Harvard researchers found that the blue light emitted from these devices can disrupt your body’s natural circadian rhythm and suppress melatonin. This is the hormone that makes you sleepy at night.

If hot flashes and night sweats keep you up at night, Dweck recommends a cool shower before bed and breathable pajamas.

Also avoid caffeine and alcohol, especially red wine, which are known triggers for hot flashes, she says.

The best starting point for getting back in tune with your body as you enter your 40s is to keep a heart-healthy diet and exercise.

If you’ve already got this foundation down but don’t feel your body is responding, try varying up your workout routine to awaken new muscles or eating a new diet to give your gut a jolt.

Sometimes tackling changes isn’t about doubling down with the same routine, but finding a new one that works for you.

Christine Yu is a freelance writer, covering health and fitness. Her work has appeared in Outside, The Washington Post, and Family Circle, among others. You can find her on Twitter, Instagram, or at christinemyu.com.