Weight and fertility: 6 science-based tips

A woman’s fertility is highly individual. Many factors can influence your ability to conceive, such as age, lifestyle, genetics, stress, and even weight.

I know weight can be a challenging topic, but as a nutritionist, it’s my job to look at the science behind the number on the scales (don’t worry, it’s not too scary!).

Below is a summary of the current research on weight and fertility, as well as some science-based tips to support you on your journey to becoming a mother.

Weight and fertility: The science at a glance

Several studies found an increased risk of infertility in both underweight (BMI <19) and overweight (BMI >25) women. The risk for infertility is lowest among women of average weight (BMI 19-25).

The science strongly suggests maintaining a healthy weight could reduce the risk of infertility and improve your chances of becoming pregnant.

Low weight and fertility

Underweight women may experience irregular menstrual cycles and malnutrition – two things that can interfere with your body’s ability to support and nourish a growing foetus.

If you think about it, nature ensures that only healthy organisms, who are capable of maintaining a healthy pregnancy, are reproducing.

It’s possible to get pregnant if you’re underweight, but it often takes a long time. Research shows that underweight women take an average of 29 months to conceive, while women with a ‘normal’ weight profile take an average of 6.8 months.

Of course, many underweight women eat nutritiously and just happen to have smaller frames. If this is you, it’s a good idea to pay extra attention to your diet while you’re trying to conceive to ensure you’re getting sufficient calories.

Obesity and fertility

There is an increased risk of infertility for overweight women (when compared to women in the normal BMI weight range), but it’s obesity that poses the most complications.

Obesity is classified as a BMI above 30 and is linked to menstrual disorders, miscarriage, and poor pregnancy outcomes. It may also lead to insulin resistance, polycystic ovarian syndrome (PCOS), and impaired endocrine function.

Of course, every body is different, and BMI is not always a perfect science. If you have any concerns, it’s a good idea to seek qualified, professional support to help you better understand your risk factors.

Six science-based tips for a healthy preconception diet

In today’s marketing-saturated world it can be difficult to know how to eat, let alone what to eat. From intermittent fasting to Paleo to Keto, we’re drowning in information overload.

I don’t believe in fad diets or extremely rigid eating plans. I believe, at its core, proper nutrition is simple and revolves around real, whole foods. The science supports me, too.

Here are six science-based tips for eating well when you’re trying to conceive.

  1. Eat more plant-based protein

A small number of studies have found that increasing protein intake (particularly from plant sources) could help to normalise menstrual cycles in women suffering from PCOS. This could be because when you eat more protein, you tend to eat less simple carbohydrates, which can lead to weight loss.

Either way, increasing your intake of plant-based protein is a great rule of thumb for eating sufficient nutrients.

  1. Consider the Mediterranean diet

The Mediterranean diet is not a fad diet. It’s a way of eating that focuses on wholesome, unprocessed foods such as fruits, vegetables, whole grains, fish, legumes, nuts, and poultry.

One study of women undergoing IVF found a 40% increase in successful pregnancies in those who adhered to the Mediterranean diet.

The Mediterranean diet has also been linked to healthier pregnancies and pregnancy outcomes.

  1. Eat more fruit

Fruit gets a bit of a bad rep in low-sugar circles, but it’s still one of nature’s nutritional powerhouses.

One study found women who ate more fruit took less time to conceive and enjoyed less risk of infertility. Women who ate fruit 3+ times per day were up to 29% less likely to be infertile compared with women who ate very little fruit.

  1. Avoid fast food

In another study, women who ate no fast food experienced a 24% reduction in the time it took them to conceive when compared to women who ate fast food four or more times per week.

The study also found eating no fast food reduced the risk of infertility by 41%!

  1. Move your BMI into the healthy weight range

If you need to gain weight:

  • Try eating smaller meals more frequently to avoid overwhelming your small tummy.
  • Add more good fats into your diet such as avocado, chia seeds, nuts, and seeds.
  • Incorporate more whole grain carbohydrates.
  • Decrease your exercise levels if needed. Heavy weight lifting can disrupt your hormone levels as well as decrease your body fat percentage. Keep resistance (weight) training to 30 minutes three times per week, and cardiovascular (walking, running, biking) to 30-40 minutes three to four times per week.

If you need to lose weight:

  • Decrease fat from unhealthy sources such as meat, eggs, butter, and baked goods.
  • Maintain or increase fats from avocados, chia seeds, nuts, and seeds.
  • Replace simple ‘white’ carbohydrates with whole grains.
  • Incorporate exercise into your weekly routine by following a similar plan to the one outlined above (under the gain weight section).

  1. Practice mindful eating for portion control

As a mum of two kids under five, with a full-time job, I totally understand busy. I often get through the day and need to think hard to remember what I had for lunch or if I even remembered to have breakfast.

Equally, I might go to grab something out of the pantry and not be able to find it – because I probably ate it all without realising.

We ALL need to work on mindful eating. You can practice it very easily.

  • Next time you have a snack, make sure you sit at the table to eat. No distractions – no TV, no cell phone, etc.
  • Take one bite/mouthful at a time. Really taste it. Feel the texture in your mouth. Is it hot or cold food? Rough or smooth? Squishy or crunchy? Does it dissolve or break apart?
  • Take your time and notice how full you’re getting. Stop when you feel comfortable. The rest can get saved for a snack for later or lunch tomorrow.

Final thoughts on weight and fertility

Fertility is complex, and there is no one-size-fits-all solution (if only someone could wave a magic wand!). What these studies suggest is weight is a key piece of the fertility puzzle, so it’s worth paying attention to if you’re trying to conceive.

If you’d like further support and guidance, please book a free 15-minute consultation. In this time, you’re welcome to ask me your top weight and fertility questions (you’ll be surprised at how much ground we can cover in just 15 minutes).

Book your free 15-minute consultation today.



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