Mounjaro could theoretically improve fertility by impacting weight loss, blood sugar levels, and hormone health.
However, research has yet to investigate the impact of Mounjaro on fertility, so our understanding of this is primarily based on research examining the effects of weight on fertility.
Many factors influence fertility levels, pregnancy chances, and the likelihood of successful live birth.
While genetics, environmental factors, and certain health conditions play important roles, emerging scientific evidence suggests that metabolic health significantly impacts reproductive function.
For individuals considering fertility treatment or trying to conceive, understanding the relationship between weight management and reproductive health is crucial.
While research shows that achieving a healthy weight can improve fertility outcomes, how we approach weight loss is important.
Some studies have shown that weight loss without a period of weight maintenance doesn’t improve fertility, whereas weight loss followed by a period of weight maintenance does improve fertility and live birth rates.
Additionally, as we don’t know the direct effect of Mounjaro on female fertility and ovarian function, it’s recommended to come off of the drug one month before trying to conceive or going through IVF treatment.
So, using Mounjaro to support weight loss could improve fertility. Still, it would need to be approached in a sustainable way, ensuring there’s a period of weight maintenance a few months before trying to conceive.
We’d recommend letting your GP know if you start taking Mounjaro.
How does Mounjaro work?
Mounjaro is a dual-action weight-loss injection. It supports weight loss by mimicking two hormones, GLP-1 and GIP, that communicate with the brain’s appetite control centre, the hypothalamus, to lower hunger and food-seeking behaviour.
The drug in Mounjaro is tirzepatide.
By lowering hunger and our desire to eat, Mounjaro helps us eat fewer calories to achieve a calorie deficit.
A calorie deficit occurs when we consume fewer calories than our body needs to fuel its essential functions, such as digestion, blood flow, and brain function.
By creating a calorie deficit, our bodies will ‘burn’ the excess fat stored for energy, and we’ll lose weight.
Mounjaro also slows down the rate at which we digest food so that our stomach and gut send signals to the brain to signal the feeling of fullness.
So, Mounjaro supports weight loss by making us feel less hungry through two mechanisms:
- Communicating with the brain’s appetite control centre
- Slowing the rate that food is digested
Randomised controlled trials have shown that Mounjaro leads to an average weight loss of around 26% after one year.
Insulin and fertility
Understanding how weight management influences fertility requires examining several interconnected biological mechanisms.
Research has revealed that metabolic health, particularly insulin sensitivity and inflammation levels, is crucial in reproductive function.
Insulin resistance presents a significant challenge for fertility. Insulin is a hormone that regulates our blood sugar levels as well as having other essential functions in the body.
When the body becomes resistant to insulin’s effects, it must produce more insulin to manage blood sugar levels.
This excess insulin can disrupt the delicate balance of reproductive hormones in several ways:
First, high insulin levels can trigger increased production of androgens (like testosterone) in the ovaries.
When androgen levels become too high, they can interfere with normal egg development and ovulation.
Second, insulin resistance affects how fat is stored in the body. It often leads to increased visceral fat – the type stored around internal organs – and causes existing fat cells to enlarge.
These enlarged fat cells become dysfunctional, releasing inflammatory proteins that create a cycle of increasing insulin resistance and hormonal imbalance.
Does weight loss improve fertility?
However, the relationship between weight loss and fertility is more complex than it might appear.
Observational studies have shown an association between weight and rates of pregnancy, live birth rates, and time to pregnancy during IVF treatment.
There’s also an association between BMI and the levels of a hormone called AMH, which predicts the number of ovarian follicles – a key marker of fertility.
This might be due to the relationship between our fat cells, insulin resistance, and inflammation.
Insulin resistance can lead to excess visceral fat levels (the fat stored in and around our internal organs), which releases pro-inflammatory proteins into the bloodstream, promoting more insulin resistance and disrupting our hormonal balance.
Insulin resistance can also increase fat cell size in your subcutaneous fat (the fat stored beneath your skin).
When this happens, these fat cells become dysfunctional and release pro-inflammatory proteins into the bloodstream, worsening insulin resistance and disrupting hormone balance.
This was demonstrated in a randomised controlled trial in 49 women comparing the effect of a weight loss intervention before fertility treatment to a control group where the participants completed the fertility treatment only.
The participants in the weight loss group underwent 6 weeks of a low-calorie diet to induce weight loss, followed by 6 weeks on a weight maintenance diet.
The study showed that participants in the weight loss intervention – who achieved an average weight loss of 6.6kg compared to 1.1kg in the control group – had higher pregnancy rates (48% vs 14%), live birth rates (44% vs 14%), and fewer cycles of IVF to pregnancy (two vs four) compared to the control group.
Contrastingly, two large randomised controlled trials with over 800 women have shown very different results.
The participants in both trials underwent a lifestyle programme lasting between 12-16 weeks before undergoing fertility treatment while following a very low-calorie diet (1200/day).
Despite significant weight loss in both trials, the results showed no difference in pregnancy and live birth rates compared to the control groups who completed fertility treatment only.
This seems counterintuitive. However, it’s possible that as there was no period of weight loss maintenance in the larger trials, the participant’s bodies were under more stress due to the strict dieting regime. This may have had an impact on their ovarian function.
During severe caloric restriction, the body enters a phase known as ‘metabolic adaptation’ that lowers energy expenditure, disrupts the balance of our reproductive hormones, and can affect ovarian function.
Animal research has found that calorie restriction can reduce fertility by affecting ovarian follicle development.
However, after a period of weight maintenance, there’s an improvement in ovarian function compared to the baseline (before weight loss).
It’s possible that losing excess body fat and improving insulin resistance in the long term enhances fertility and your chances of conception, but trying to conceive during or immediately after a period of rapid weight loss and strict calorie restriction may harm your chances of pregnancy.
Take home message
While Mounjaro hasn’t been directly studied for its effects on fertility, its ability to improve metabolic health may theoretically support reproductive function.
The key appears to be a strategic approach to weight loss that includes:
- Gradual, sustainable weight loss
- A period of weight maintenance
- Coming off the medication one month before trying to conceive
- Eating a diet based on whole foods
- Focusing on other healthy habits like sleep and exercise
Remember that fertility is influenced by many factors, and weight loss is just one piece of the puzzle.
Second Nature’s medication programmes
Second Nature has two medication-supported programmes: a Wegovy weight-loss programme and a Mounjaro weight-loss programme.
For peace of mind.
Second Nature has worked with the NHS for over 6 years, providing weight-loss programmes across the UK.
While our Wegovy and Mounjaro weight-loss programmes are private and not currently used by the NHS, we’ve built the programmes focusing on scientific evidence, patient safety, and data security.
We hope that our 6+ years of working with the NHS and building a track record of effective weight-loss results will give you peace of mind to give us a try.
