The Power Struggle of Postpartum Hormones & Weight Loss

When I was pregnant with my first daughter, I was working on a hospital clinical rotation as a physical therapist, and I was VERY pregnant. I’ll never forget a medical billing woman there, speaking to me and 4 pregnant nurses, telling us all that she left the hospital after her first baby wearing her pre-pregnancy jeans. I remember rolling my eyes internally, but at the same time also thinking, “I’m fit, I eat right, I never stop moving…. it’s possible.” I had gained 65 lbs with my pregnancy despite my excellent lifestyle habits, but it was possible.

Flash forward to 4 months postpartum from a c-section, still up 40 lbs from my baseline, working out 6 times a week, discouraged and sobbing to a nurse practitioner. Her words - “you will not drop all of the weight until you’re done breastfeeding.”

Until that point, hormone imbalance hadn’t crossed my mind as more than in passing. After all my PT schooling and fitness experience, I still couldn’t see it - that all the articles and blog posts in the world about melting off the pounds while breastfeeding were not reflective of the truth for a lot of women. In fact, many women DON’T shed the pounds while breastfeeding, and not just because they’re extra hungry. And even if you’re formula feeding from day 1, the weight may not just simply doesn’t fall off. Why?

HORMONES

In this post, we’ll cover some of the biggest name hormones involved in pregnancy and postpartum - what they do, how they fluctuate during all these transitions, and what effect they have on body fat and muscle building. This information is educational, sure, but the biggest purpose it’s served for me? Reassurance that, although it might not have been visible on my body in the first few months, my efforts during the more immediate postpartum months are not in vain. And the same is true for you!

Before I talk about hormone levels, it’s important to state I’m not an endocrinologist. When I say “high” and “low,” I don’t mean pathologically high or low - I mean fluctuating hormone levels within a healthy and normal range. If you’re having symptoms that you believe need medical attention, please do not hesitate to call your doctor and seek further follow up care. I also want to be sure we don’t make hormones our primary culprit - hormones are one in a laundry list of factors that affect our individual ability to lose weight and build muscle. However, it’s important to be educated about our bodies from all perspectives so we can optimize what we can and approach weight loss realistically. Ok, let’s get to it.

Relaxin makes room for baby, but with a catch

Relaxin is a reproductive hormone that spikes during the first trimester to relax muscles (both skeletal muscles and muscles in your organs), joints, and ligaments during pregnancy so that your body can expand in size to accommodate for baby. It drops for a while, and then spikes again to target your cervix and uterine lining to softening/widening your cervix to prep for birth. And the research is beginning to show that it also has a target destination of your SI joint - where your spine and your hips meet (where you might have a back dimple), a major area of shock absorption every time you take a step.

What does this mean for you?

• Increased risk of injury at every joint, as the passive stability provided by your ligaments is no longer as strong and your body is relying on muscular strength to keep it stable instead.

• Mildly less tolerance to aerobic exercise as your arteries relax by 30-50% to accommodate greater blood volume

• Heartburn when your GI system becomes more relaxed

• Back pain, especially later on in pregnancy and in the first few months after childbirth when your core and trunk stability is at its lowest

• Diastasis recti (ab separation) as your abdominal muscles move apart to accommodate baby and strain to try and stabilize your trunk where the ligaments are looser

• Foot pain and increased shoe size as your arches flatten and your feet swell

Relaxin takes at least 5 months to clear - and some sources say up to TWO YEARS! Therefore, it’s important to maintain strength and stability at your joints to prevent injury as your body undergoes a whole new set of physical stressors caring for a newborn baby into toddlerhood.

Prolactin - not just the milk maker

Prolactin is a really interesting one. It’s best known for its role in lactation and breast development, but this amazing hormone is responsible for over 300 functions in the body - including metabolism regulation.

When you’re breastfeeding, it only spikes during suckling… but as nursing moms know, that can be a big portion of your day, especially during a cluster feed! And while it’s spiked, prolactin stimulates appetite and reduces fat metabolism so your body actually preserves fat.

Formula moms: you still produce prolactin as your body naturally expects to breastfeed. Within 7 days, prolactin typically approaches normal when your body realizes it’s not nursing.

On the whole, prolactin levels fall about 50% right after birth and decline with time towards baseline. By 6 months, prolactin levels during the times of day a mom is NOT breastfeeding is effectively back to normal, with spikes only happening during nursing sessions to promote milk production.

In a big review of studies, it was shown that reduced prolactin results in reduced fat and high prolactin (pathologically) is actually linked to obesity. What’s this mean for you? As long as you’re nursing and prolactin levels are spiking throughout the day, prolactin is still coursing through your bloodstream at elevated levels at some point…

In the short and short - high prolactin while nursing primes your body to continue to increase your appetite and store fat so your body can make enough milk to feed your baby.

ESTROGEN promotes storing energy as fat in abdomen and thighs/glutes

Estrogen is a tricky one. It’s gotten a bad rap in the fitness world for years as a a harbinger for fat storage - but in reality, estrogen has different effects in different women, and that’s because there are multiple different types of estrogen receptors in different parts of the body, and those different types of receptors store or burn fat in different areas and in different ways.

In short, estrogen is responsible for fat storage - it’s what makes a woman’s body look womanly - but it also helps us produce lean muscle mass when properly balanced with other hormones in the body.

Two main receptors for estrogen are estrogen-alpha, and estrogen-beta.

Estrogen-alpha: highest density in the abdomen. It’s responsible for fat burning effects all over the body, but forms fats that are stored in the abdomen when levels are low. This receptor goes low when you’re under high stress, or if you have low progesterone (like right after birth)… and so it goes, you store energy in belly fat.

Estrogen-beta: highest density in the back of the arms, the thighs, and the glutes (as well as the ovaries, the uterus, and the bladder…). It’s responsible for increased fat storage (in the areas it’s found most) and a decreased metabolic rate. It also impairs insulin sensitivity and glucose tolerance — which stores sugars in your body as fat.

(confusing, but you can read more by Marek Doyle in this article).

So basically - estrogen plays double duty to both store fat and help us burn fat. And when levels are low (immediately after birth!), it’s telling the body to store fat, which is preventing the body from creating lean muscle mass. Which is why estrogen is a catch 22 — too high, and estrogen also stimulates the body to store fat, but you need higher levels to create the lean muscle mass by fostering a more forgiving metabolism and reducing sensitivity to carbs.

PROGESTERONE supports metabolism of stored fat so you can burn it as energy

Progesterone is the ultimate moderator - a gatekeeper that up- or downregulates the expression of other hormones and their effects. In the pregnancy and postpartum period, importantly, progesterone is a huge moderator for estrogen. This hormone spikes when you’re pregnant, helping to stimulate the thickening if your uterine lining and prevent you from ovulating the whole time you’re pregnant. Thus, it’s maintained high throughout an entire 9 months. You need progesterone to moderate the levels of estrogen in your body, to prevent estrogen dominance - aka, progesterone keeps estrogen from going haywire. And it’s important in pregnancy for fat metabolism… because we burn a lot of energy feeding baby!

When it sinks low, immediately after birth, so does estrogen - and luckily so, or else the spike in bodily estrogen would be telling your body to nonstop store fat. Progesterone has a similar type effect on other hormones as well - and as its level fluctuates, the ability of those hormones to tell the body to burn or store fat fluctuates as well. Progesterone doesn’t directly CAUSE weight loss or gain, but just modulates the effects of other hormones that do. And by promoting fat burning, metabolic processes, balanced levels of progesterone allow you to more efficiently burn energy.

ESTROGEN and PROGESTERONE play off of each other…

And their levels act similar during pregnancy and after birth. Both drop rapidly after birth also facilitates creation of colostrum, those golden droplets that feed your baby immediately after birth. Both hormones should also normalize at about 3 months postpartum, which is why you start to emerge from that “baby haze” around that time, because low levels of both can cause brain fog. Typically, these hormones are only ever both low together during your period, which is why you might feel that similar brain fog during this time.

But importantly, the key concept here is THREE MONTHS. 12 weeks of hormones dropped low that, when low, decrease your tolerance to stress, increase your body’s sensitivity to sugar and carbs, and overall cause you to maintain body fat and therefore excess weight. If weight loss is your goal… give your body TIME.

Cortisol: THE BIGGIE

Cortisol fluctuates on a typical cycle throughout the day (the sleep-wake cycle) and is key in regulating almost every organ and tissue in your body, in controlling use of protein, fats, and carbs to maintain energy, and in regulating our stress response. It’s responsible for stimulating fat and carb metabolism for fast energy — but also releasing insulin so you can maintain your blood sugar, which increases cravings. Cortisol speeds up or slows down your metabolism based on the physical and emotional stress your body is experiencing!

Along with that - it’s the number one hormone responsible for storing belly fat in your body.

So with increased stress, your body is apt to store more belly fat instead of burn it as energy.

What increases cortisol?

• Loss of sleep

• Increased emotional stress

• Poor nutrition

• Lack of exercise

• Increased physical stress

Does that sound like the postpartum months to you? What’s more, high belly fat also signals the body to secrete more cortisol, which in turn stores more belly fat because you’re stressed, and on and on we go.

TO SUM THIS ALL UP - IN YOUR HIGH STRESS, LOW SLEEP STATE AFTER BABY, YOU’RE CRAVING HIGH CARB, HIGH SUGAR SNACKS TO KEEP YOUR ENERGY UP - WHILE YOUR BODY IS PRIMED (BY HORMONES) TO STORE ENERGY AS FAT.

It’s a snowball effect.

So don’t beat yourself up! Your hormones are acting exactly as they should, to provide your body with the energy it needs to sustain you AND your baby, and this hormone reaction is HEALTHY. The aesthetics work against the fitness and weight goals we might envision, but the look you want will come with time if you stay consistent with regular exercise/strength training and a healthy, protein-rich diet in the months immediately postpartum. You’re working against your biology in the immediate term, but consistency while you normalize will pay off in time.

Stick with it!! Build your strength and stability. Create mobility where you need it. Stretch, but don’t overstretch. Give yourself grace. And as much as you want to punch every single person who says “it took 9 months to make this baby, it’s going to take at least 9 months to get back to normal!!”…. they’re right, at least when it comes to hormones.

Disclaimer: This isn’t an exhaustive list. There are others - grehlin (hunger), leptin (feeling full), oxytocin (love and bonding), and more - but some of the biggest players are listed above. I’m not an endocrinologist (hormone specialist), or a naturopath, or functional medicine provider, or a nutritionist. I AM a physical therapy doctor, strength coach, and postpartum/pregnancy fitness specialist who reads the research and has both seen and experienced the effects of hormones on womens’ bodies. If you are concerned with a hormone imbalance, please seek help from your medical provider or email me for information on the best person to reach out to for your issue.