How your weight affects your fertility and conception
Kathryn came to see me almost two years ago. She’d had numerous in vitro fertilisation or IVF cycles without success, and as she had been diagnosed with hypothyroidism she was referred to see me. She was overweight with a body mass index (BMI) of 42 and had 51 per cent body fat (see Chapter 3 for a full explanation of BMI and body fat percentage), and what was even more difficult for her was that the more IVF hormones she took, the more weight she gained. Although she had lost 3 kilograms before coming in to see me, she found that she just couldn’t lose any more (well, lose it and keep it off, anyway). Kathryn is smart, well educated and had a generally healthy diet, so she was incredibly frustrated at why she couldn’t lose any more weight, or get pregnant.
After taking a comprehensive assessment, I calculated exactly how many serves of carbohydrates, fats and protein Kathryn required each day to optimise her intake. I wrote her a plan, and over the next few consultations, I taught her how to calculate her servings herself.
After losing 17kg, Kathryn finally got pregnant, and as I write this she is now in her third trimester of pregnancy.
One in six couples will struggle to get pregnant. Infertility can be caused by physical or medical conditions such as damage to the fallopian tubes or early menopause; however, nutrition, lifestyle habits and weight play critical roles. Trying to have a baby when you are overweight or have poor nutrition is like trying to grow a plant in a cupboard without any sun – it is just not the right environment for growth.
So, let’s look at why your weight and what you eat are so important for getting pregnant . . .
How being overweight affects your fertility
Research tells us that for every point over a BMI of 29, your chance of falling pregnant decreases by 4 per cent. That means that a healthy woman with a BMI of 45 has 60 per cent less chance of becoming pregnant than if she lost weight and got down to a ‘healthy’ BMI of 25. Furthermore, women who are overweight who undergo IVF have almost double the chance of miscarriage as women with a BMI between 20–25.
But it’s not just women with a high BMI who can have problems conceiving. BMI is only one measure of weight, and it’s not always the best indicator. Many women can have a BMI within the ‘healthy’ weight range but have a high percentage of body fat. So even if you are a size 8, if your percentage of body fat is too high your ability to conceive will be affected. If you are struggling to conceive, ask your GP or dietitian for a referral to have your body composition analysed, and if your percentage of body fat is too high, discuss with your dietitian how to decrease your percentage of body fat without losing any muscle mass.
But how can having too much body fat make it difficult to conceive?
The health of your eggs
If you live in an area where there are no parks or footpaths, iridescent signs beam advertisements for soft drinks whichever way you turn and there’s a takeaway food outlet on every corner, it’s much harder to be healthy than if you live in an area with plenty of green space, walking tracks and fresh food markets. It’s the same for our eggs. Our eggs are produced in our ovaries, and the health and quality of our eggs are dependent upon the environment of our ovaries. Studies show that women who are overweight have abnormally high levels of fat and inflammation in the fluid surrounding their eggs, which affects the developmental potential of their eggs.
Eggs from women with obesity have been found to have ‘disorganised’ DNA, the molecule that contains the genetic code that helps to create new life. As the DNA isn’t in all the positions that it should be, it is believed to be a key reason why it is more difficult for women who are overweight to have their eggs fertilised – even with Assisted Reproductive Technology (ART) such as IVF.
The release of your eggs
The menstrual cycle, and the ability to ovulate or produce an egg are regulated by hormones. Oestrogen, luteinising hormone (LH), follicle stimulating hormone (FSH), gonadotropin releasing hormone (GnRH) and progesterone all dance in a finely tuned choreography to create the right environment for conception.
Contrary to what many people think, our stored body fat, or adipose tissue, is actually a metabolically active tissue undertaking many chemical reactions, just like our other tissues, such as our muscles, bones and blood. One role of adipose tissue is the production of oestrogen. If a woman carries too much body fat, the combination of oestrogen produced by the ovaries and oestrogen produced by adipose tissue can result in an overproduction of this hormone.
During menstruation, oestrogen levels are at their lowest. This signals the brain to produce FSH to begin maturing more eggs for ovulation.
If a woman’s oestrogen is chronically high, hormone production becomes out of balance, weakening the signal for the body to commence maturation of eggs and thereby affecting her ability to ovulate. As such, women who are overweight or obese are up to three times more likely to experience irregular periods and less regular ovulation, making it much more difficult to conceive. In fact, about 30 per cent of infertility is thought to be caused by oestrogen imbalance.
Insulin resistance is another common cause of infertility. It is estimated that 60 per cent of people who are overweight have insulin resistance, although many people go undiagnosed.
Insulin is a hormone that is involved in digestion, among many other important functions. Women who have insulin resistance find excess body fat forms a barrier to insulin trying to get through to the bloodstream, rather like a condom to sperm, so that it can’t get through and work effectively. As a result, women with insulin resistance produce more and more insulin – a condition called hyperinsulinemia – as their body tries to produce enough of it to get it to the glucose calling out for it in the bloodstream. In turn, this imbalance leads to carbohydrate cravings and more weight gain. The excess body fat will then produce higher levels of oestrogen, resulting in an increasing spiral of excess insulin production and excess fat deposition, followed by excess oestrogen production.
In addition to affecting oestrogen levels, insulin resistance also impacts the production of progesterone and luteinising hormone, further altering the hormonal environment of the ovaries and impacting fertility.
A landmark study undertaken in 2010 on mice found that the pituitary gland responds to chronically high levels of insulin by triggering a cascade of hormonal changes which impair fertility. Lean mice had six times more successful pregnancies than obese mice. Obese mice which had their pituitary-insulin receptors removed had five times more successful pregnancies than obese mice with their pituitary-insulin receptors intact. What does this tell us? That our hormones have a big impact on our ability to fall pregnant. And our weight has a big impact on our hormones.
Even if you are having regular periods and have healthy eggs, to become pregnant you need sperm. And to get sperm inside your vagina, you need to have sex (or Assisted Reproductive Technology). A study by Brody and colleagues found that women who are obese are less likely to have sex with their partners than women who are a healthy weight. It was suggested that their diminished sexual desire may be a result of increased serotonin levels as a result of overeating. The key message here? If you want to have a baby, reduce your portion sizes and enjoy more frequent sex.
Let’s go back to our high school sex education class. After your egg is fertilised by your partner’s sperm in your fallopian tube, it continues to travel down your fallopian tube and implants itself in the lining of your uterus. It is believed that being overweight impacts the environment of the uterus, making it more difficult for your embryo to implant and receive the nourishment that it needs for survival.
Futhermore, being overweight increases the risk of having a miscarriage by 3 per cent, particularly within the early stages of pregnancy. Please don’t get me wrong, I’m not saying that if you are overweight you’re going to have a miscarriage, it’s simply that your risk is higher – which is a good reason to lose weight before conceiving, and to really focus on doing everything that you can for a healthy pregnancy. There have also been suggestions that the genetic profile that increases someone’s risk of being overweight may be linked to the genetic profile that increases that person’s risk of having a miscarriage. We can’t change our genetics, but we can change what we eat.
‘Studies have shown that obesity, particularly in association with PCOS, results in a significant decrease in spontaneous pregnancy rates due to disordered ovulation. As a result, there is an increased need for artificial reproductive technologies, such as ovulation induction and IVF. Even with these techniques, there is a decrease in response to the fertility drugs, a decrease in success rates, increased miscarriage rates and even an increase in the rate of Caesarean section at delivery.’
Assoc Prof Peter Lutjen, National Medical Director, Monash IVF
Your diet affects your fertility
Our diet has a significant impact on our fertility. Research by Harvard Medical School found that women who have a higher ratio of good fats, a higher intake of plant-based protein foods, a diet with a lower glycemic index, a diet which meets recommendations for dairy products, meets iron requirements, those who use vitamin supplements, have a healthy weight and undertake the recommended amounts of exercise each day have the least likelihood of experiencing infertility. Furthermore, those who adopted just five of these lifestyle measures had a 69 per cent reduced infertility rate compared to women who adopted none.
A review by Cetin and colleagues explains that although rates of obesity are increasing, micronutrient intakes such as omega-3 fats, folate and calcium are decreasing, which has a significant impact on rates of fertility. When you stop and think about it, it makes sense really, doesn’t it? The healthier you eat, the better your body is going to function, and the greater chance you have of becoming pregnant. For more details on recommended dietary intakes to optimise your fertility, see Chapter 4.
Weight related medical conditions that may reduce fertility
You may have heard of polycystic ovarian syndrome and diabetes. These medical conditions, among many others, are more common in women who are overweight, and they make conception more challenging. If you’re overweight and struggling to become pregnant, the first step is to have a thorough check-up with your GP or doctor, and test for any medical conditions. Then find a good dietitian who can work with you on your diet and weight to help minimise the effects of any of these medical conditions as much as possible. Common medical conditions to check for include polycystic ovarian syndrome, diabetes, thyroid conditions, Cushing’s syndrome and endometriosis.
Polycystic ovarian syndrome (PCOS) affects 12–21 per cent of women of reproductive age. PCOS is caused by insulin resistance in approximately 80 per cent of women with the condition. In women with PCOS, high insulin levels result in development of cysts on the ovaries. Ovarian cysts produce another hormone called testosterone, which, in excess, has a domino effect on other hormones and results in reducing the body’s ability to ovulate.
As having a high percentage of body fat is one of the main causes of PCOS, weight loss and dietary changes can do wonders for this condition. In our practice, we have seen women with more than 20 ovarian cysts, who, as a result of weight loss, carbohydrate counting, exercise and commitment, decrease to no cysts.
Diabetes is a condition where the body has trouble keeping glucose levels within the recommended ranges in the bloodstream. Women with diabetes have an increased risk of infertility for a number of reasons. They may go through menopause earlier than women who don’t have diabetes. A very high percentage of women with diabetes also have insulin resistance, and those who don’t have well-controlled blood glucose levels have an increased risk of spontaneous abortion, foetal abnormalities and pregnancy complications. If you do have diabetes, it’s essential that you get your blood glucose levels under control to optimise your fertility.
Disorders of the thyroid gland such as hypothyroidism (too little thyroid hormone) or hyperthyroidism (too much thyroid hormone) can disrupt the menstrual cycle and thereby reduce fertility.
This is a hormonal condition where the body produces too much cortisol hormone. It also results in rapid weight gain and irregular or non-existent menstrual periods, making it challenging to become pregnant.
Endometriosis is a condition where the cells lining the uterus grow outside the uterus. Approximately 30–50 per cent of women with endometriosis struggle to conceive. Although there are many theories about what causes this condition, the truth is still unknown. Endometriosis does not cause weight gain, nor is it caused by being overweight, but some of the common treatments for endometriosis can result in weight gain as a side effect. Furthermore, research suggests that there may be a link between diet and endometriosis. For example, a study by Britton and colleagues in 2003 found that women who had a high intake of fruit and vegetables were less likely to have endometriosis.
What to do if you’re overweight and struggling to conceive
As I mentioned earlier, the first step is to ask your GP or doctor to give you a health check. Any medical conditions such as PCOS, insulin resistance or diabetes need to be diagnosed and treated. Then you need to make a concerted effort to try to lose weight to help optimise your hormone production. Weight loss can be more difficult in women who have medical conditions such as PCOS or insulin resistance, so be patient. A dietitian will be able to tailor a meal plan to your specific medical and nutritional requirements that also fits your lifestyle. Optimising your ratio of carbohydrates, proteins and fats is essential for fertility. (See Chapter 6 for information about nutrition and optimising your weight before pregnancy.)
Being underweight can decrease your fertility as much as being overweight. When Rita first came to see me she was 32 years of age, and had successfully beaten anorexia nervosa and bulimia nervosa. She was an incredibly strong woman, and had learnt a lot over the years. Her husband, Mark, was a very loving man and a huge support. Now that she was healthier, she desperately wanted a baby, but they’d been trying for a few years and were struggling to conceive.
Although Rita was in control of her eating disorder, her percentage body fat remained low at 10.5 per cent and she weighed just on 51 kilograms for her 164 centimetre frame. Furthermore, she continued to exercise for over 60 minutes per day, seven days per week. Her doctor had advised her to gain some additional weight to assist with her fertility, but she was having an internal battle about this.
Rita and I discussed why weight gain, and fat gain in particular, is so important for conception. Once she got her head around this, we were able to slowly increase her body fat using healthy fats and larger portions and also reduce the amount of exercise she was undertaking. At 55 kilograms, she became pregnant.
Although being overweight reduces fertility, being underweight also affects the production of hormones, making ovulation more challenging. I often see female athletes, or women who have had previous eating disorders with low levels of body fat, who struggle to get pregnant. Trying to conceive can be an extremely challenging time for these women as although they desperately desire a baby, the need to gain body fat is confronting.
Not all women with a low percentage of body fat have eating disorders; some of them simply have a fast metabolism. But whatever the reason, increasing body fat can be important for fertility. Contrary to the images of skinny models that we see in the media, women are designed to have higher levels of body fat than men. We need a bit of extra body fat to protect our reproductive organs, produce oestrogen to regulate our hormones and store energy for breastfeeding. If you have a low percentage of body fat, try to increase it by increasing your portion sizes and your intake of healthy fats such as avocado, nuts and olive oil in your diet. This additional body fat will help to optimise your hormone levels and enable you to ovulate.
To gain additional body fat, start by checking that you are eating adequate amounts of all of the five core food groups: wholegrains, vegetables, fruit, protein foods and low-fat dairy products. If you struggle to fit all the food in, try eating smaller amounts more frequently. Focus also on increasing your intake of good fats, such as fish, avocado, nuts, seeds and olive oil. Try adding extra olive oil to your evening meal, putting tinned tuna or avocado on dry biscuits for lunch, and a few tablespoons of crushed nuts on your breakfast cereal. You can also swap water for drinks containing more kilojoules, such as freshly squeezed juices or smoothies. You don’t need to gain heaps of extra weight, but eating a healthy diet and a small increase in body fat might be just what your body needs to provide the right environment for you to conceive.
Your partner’s weight and diet is essential too
Not only is your weight and diet essential for optimal fertility, but your partner’s is too. Forty per cent of fertility problems can be traced to our other half. I have never seen someone more ecstatic than Pete when he came into my clinic and told me his wife was pregnant. Pete had struggled with his weight for years after a car accident had caused permanent damage to his back. Before the accident he loved playing sport, but since the accident he could barely walk and the kilos had piled on. As a sporty person, he used to be able to eat whatever he wanted and get away with it – from a weight point of view anyway.
When he first came to see me, Pete was at his wits’ end. Over the subsequent months we worked on changing his diet to reduce the kilo-joules he was eating. Pete confided that losing weight and getting rid of his CPAP (continuous positive airway pressure) machine for his sleep apnoea had done wonders for his confidence and libido. He now has a baby girl, Tracey, with baby number two on the way.
So, what can our partners do to improve their fertility? Research suggests that a man who is just 10 kilograms overweight has a 10 per cent reduction in fertility, and for every three additional BMI points over a BMI of 26, a guy’s fertility is decreased by another 12 per cent. For a man, being overweight impacts fertility in a number of different ways, including decreasing sperm count, affecting the quality of sperm and decreasing sex drive. Being underweight is also associated with diminished fertility, so now is the time for you both to focus on your weight and health.
Just as it does for women, stress can decrease male fertility. It can also contribute to weight gain. Stress increases the production of a hormone called cortisol which can increase hunger and also result in accumulation of fat around the waist. If stress is a big issue for your partner, sit down together and work out the causes of stress and some practical strategies for decreasing stress in his life. He may consider prioritising more sleep and relaxation time, planning some enjoyable activities or holidays for the two of you, getting more exercise and trying to adjust his social and work commitment schedule to allow for more down time. You could also encourage your partner to consider talking to his GP or a counsellor to help with implementing some stress-busting strategies and get more support.
Nutrition has a direct impact on the quality of a man’s sperm, so drinking less beer, eating less pizza, and eating more healthy, home-cooked meals will make a positive contribution. I’m sure that you’ve heard the old wives’ tale about oysters being an aphrodisiac – well, there’s actually science behind it to prove it’s true. Oysters are one of the richest sources of zinc, and low zinc levels are renowned for decreasing testosterone and causing a lower sexual appetite.
Zinc is also essential for sperm volume. Zinc deficiency isn’t so common these days, as red meat is also a great source of zinc and, according to research, most men get plenty of it, if not too much. But if your guy is vegetarian, has had some type of gastrointestinal surgery or condition that affects his absorption of nutrients, then it might be worth double-checking that he is meeting his zinc requirements. Unfortunately there are no reliable tests for assessing zinc levels, so make an appointment with a dietitian to add up his daily zinc intake. If everything seems okay, aim for 200–300g (two or three 100g serves) of lean red meat each week to assist with zinc levels and other key nutrients, such as B12, omega-3 oils and protein.
Foods rich in antioxidants such as vitamin C are important to decrease the risk of sperm defects. To increase your partner’s intake of antioxidants, ensure that he is getting a wide variety of fresh fruit and vegies every day. The more different types of fruit and vegies he eats, the greater variety of antioxidants he will get. Stir fries and soups are great for packing in the vegies, so try adding an entrée of vegetable soup before your evening meal or having a side salad with your meal. Because low-starch vegies are so low in kilojoules, you can never have too many.
A low intake of folic acid is also believed to lower sperm count, so ensure that your man is getting plenty of folic acid too by including green leafy vegetables in his diet each day.
Vitamin D is another key nutrient for sperm quality. As the sun is the best source of vitamin D, check that your man is spending enough time outdoors each day. Maybe he could play a round of golf, you could go to an outdoor pool before work each morning together or he could spend some time working in the garden. Vitamin D deficiency is a significant issue in Australia, so I recommend that your partner gets a blood test to check his levels. He may need vitamin D supplements to help him meet his requirements.
It is well known that alcohol and drugs decrease testosterone levels and sperm count, and can increase the number of abnormal sperm. So while the occasional drink is okay, if you’re planning to have a baby this is not the time for too many big nights.
Achieving a healthy weight is not about aesthetics, but is essential for optimising you and your partner’s ability to conceive. I know that maintaining a healthy weight isn’t always easy in our culture of remote controls and fast food outlets, but it can be done – I’ve seen thousands of clients achieve their goals, and you can too. I’ll be here to guide you through every step of the way.
Excerpted from The Pregnancy Weight Plan by Melanie McGrice. Copyright © 2013 by Melanie McGrice.
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