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Does exercise increase fertility for women?

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Jump to: Three ways to ensure your exercise regime is boosting your fertility | Mix it up | Eat enough to support your activity levels | Don’t overdo it | Take home message

Improving your chances of pregnancy by increasing your fertility can be a challenge. There’s so much advice on diet and lifestyle it isn’t easy to know where to start. Exercise is no different; what type of exercise should you do? How much? Can too much exercise harm your fertility?

Evidence suggests that an appropriate amount and variety of exercise and physical activity can improve female fertility in three ways, predominantly by reducing the following:

1) Chronic inflammation
2) Oxidative stress
3) Insulin resistance

Research suggests improving these three factors will lead to a healthier balance of essential sex hormones involved in reproductive health and improve the health and function of your ovaries and oocytes (eggs). Exercise has also been shown to help alleviate pain and discomfort often experienced during the premenstrual phase.

Interestingly, physically active women are also 30% less likely to develop gestational diabetes during pregnancy compared to women who are sedentary. However, excessive exercise can also impair fertility by restricting energy availability to your reproductive system and inducing higher levels of oxidative stress.

Three ways to ensure your exercise regime is boosting your fertility

  1. Mix it up: Evidence suggests that too much high-intensity exercise (HIIT) can harm your fertility. Combining slower, more aerobic types of exercise alongside shorter, occasional sessions of HIIT could help strike the right balance. Strength training can also help to lower insulin resistance.
  2. Make sure you’re eating enough: Exercise can lower your fertility by restricting energy available for your reproductive system, so you need to eat enough food to support your exercise. You can do this by eating until you’re comfortably full, having healthy snacks available, and eating a carbohydrate snack every 40 minutes during exercise lasting longer than 60 minutes.
  3. Don’t overdo it: There’s good evidence, particularly in female athletes, that excess exercise can lead to infrequent and abnormal menstrual cycles and lower fertility. So listen to your body; if you feel tired or sluggish, have a rest day or do a calming activity like a gentle walk or yoga.

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Otherwise, keep reading as we look into three evidence-based ways you can maximise your exercise habit to ensure you’re improving your fertility and increasing your chances of a successful pregnancy.

1) Mix it up

A cornerstone of any effective exercise programme is variety. Athletes will use a variety of easy, hard, and rest days to maximise their performance. This approach can also be applied for health and fertility, as the variety can:

  • Ensure you’re training your body across the spectrum of your energy systems: this means you’ll be ensuring your body can function well at rest and during low intensities and high intensities. This will put you in a good position during the stressful period of pregnancy when everyday tasks might start to be more challenging.
  • Prevent overtraining: Excess HIIT training can harm your health and reproductive system. Ensuring variety in your exercise can prevent this and ensure you get enough slow and rest days to recover from the harder days.
  • Increase enjoyment: Familiarity breeds contempt. Doing the same hard or slow training all of the time can lead to a lack of motivation and a plateau in your training. By ensuring variety across the weeks and months, you’ll keep it interesting and your body adapting to the new stresses you put on it.

These positive effects of a varied exercise regime also seem to translate to improving the balance of essential sex hormones vital for your reproductive system.

A study involving 243 women investigated the impact of diet or a structured exercise programme (with both aerobic and strength training) on sex hormones such as testosterone, oestrogen, and SHGB.

The study showed that after four months, the women in the exercise group improved testosterone, oestrogen, and SHBG. Interestingly, both groups also lost weight, but the exercise group lost mainly excess fat, while the diet group lost a combination of fat and lean mass.

Lean mass comprises the tissues of your bones, muscles, and vital organs, and during weight loss, we generally want to avoid losing lean mass and primarily lose excess fat mass.

Similarly, a study looked at the impact of a structured exercise programme in women with and without PCOS on markers of health and sex hormones balance.

The results showed that after 12 weeks, the women without PCOS showed improvements in AMH (a hormone that indicates the number of ovarian follicles), SHGB, and visceral fat (which would indicate a reduction in inflammation and insulin resistance).

However, only some will have the time or energy to perform a structured exercise programme taking up 3-5 hours of their week, combining strength, endurance, and higher intensity exercise. Research suggests that short sharp bursts of HIIT may provide similar health benefits as aerobic training while taking up much less time in the week.

A study compared the impact of a supervised moderate aerobic exercise programme to HIIT. The moderate intensity would be for 40 minutes, four times a week. The HIIT sessions would last 20 minutes, with rest, four times a week.

Both groups saw similar improvements in sex hormone balance, with testosterone and oestrogen decreasing to healthier levels. However, the moderate-intensity group also saw reductions in fat mass – which may have led to other improvements in insulin sensitivity.

So a more structured approach to exercise that includes long periods of aerobic exercise may lead to more all-around improvements in health. If you’re struggling to fit exercise into your days, shorter, sharper bouts of HIIT may provide a reasonable solution to improve your fertility.

Key points:

  • Including various exercise activities in your week will provide you with the most all-around benefits to health and fertility.
  • This includes slower continuous bouts of aerobic exercise like jogging or cycling, alongside strength training and HIIT.
  • However, if you’re short of time and struggling to fit exercise into your regime, performing HIIT two to four times a week could be a great way of improving your fertility and health.

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2) Eat enough to support your activity levels

Many active women may restrict their calorie intake with a desire to lose weight or reach and maintain a slim figure. This is often under the illusion that calorie restriction and exercise will benefit their health and help them get pregnant.

However, this can lead to a lack of available energy to the reproductive system, which can lower your fertility and lead to abnormal menstruation.

Research shows that women who restrict their diets and have disordered eating patterns are more at risk of developing a condition known as functional hypothalamic amenorrhea (FHA), which is the absence of menstruation due to low energy intake, stress, and excessive exercise.

Low energy intake lowers fertility and leads to FHA as it suppresses the release of crucial sex hormones such as LH and FSH. FHA is also implicated in other complications, such as lower bone mineral density (increasing the risk of osteoporosis and fractures) and insulin resistance.

However, this can be managed through an increase in energy intake. A randomised controlled trial was conducted in exercising women with abnormal menstruation (amenorrhoea or oligomenorrhea).

The participants were split into two groups, one group was instructed to increase their energy intake by 20-40%, and the others were to continue their eating habits with their existing exercise patterns.

The study showed that after 12 months, women who increased their energy intake were 45% more likely to have their menstrual function return to normal. On average, the women increased their intake by 330 calories a day – equivalent to an extra three to four eggs a day or a large salmon fillet.

How can you ensure you’re eating enough?

  • Eat until you’re comfortably full: find our hunger scale here.
  • Include healthy snacks between meals if you need to: find some ideas here.
  • Avoid restricting whole food groups: find an NHS-trusted meal plan here.

Key points:

  • Strict calorie restriction and excessive exercise can lead to a condition known as FHA, which is an absence of menstruation.
  • FHA is implicated in the suppression of key sex hormones, which leads to infertility and other health conditions such as osteoporosis and insulin resistance.
  • However, research has shown that the resumption of a higher energy intake and lowering exercise levels can help menstrual cycles return to normal.

3) Don’t overdo it

Along with calorie restriction, excessive exercise can lead to lower fertility and conditions such as FHA. This can occur even in the presence of ‘adequate’ energy intake as the body is forced to provide energy to fuel the activity that would otherwise be made available to the reproductive system.

Your body can only process so many calories. When exercising excessively, you can often reach a point where eating more food won’t provide the body with enough energy to fuel your exercise, vital organs, and reproductive system.

It’s estimated that menstruation abnormalities may occur in up to 79% of women involved in sporting activities. Research has shown that female athletes are more at risk of developing abnormal menstruation and FHA.

The development of FHA through excess exercise is due to the alteration in the release of crucial sex hormones during the different phases of the menstrual cycle.

Along with chronic excess exercise, it’s suggested that one of the main factors leading to abnormal menstruation and FHA is going too hard too soon. This is a very common trait among exercisers in the general population. It can be easy to think that every session needs to leave you feeling exhausted and achy, even when you are just starting.

Fortunately, studies have shown that for women who experience FHA, stopping exercise altogether for a short time can normalise menstruation, and returning to a structured and balanced exercise programme – along with a healthy diet which is adequate in energy intake – can ensure that exercise supports a healthy menstrual cycle and improved fertility.

Here are three tips for ensuring you don’t overdo your exercise:

  1. Listen to your body and allow rest days.
  2. Don’t go too fast, too soon – increase the intensity and volume of your exercise slowly as your fitness levels improve.
  3. If you develop FHA, cease exercise, speak to your doctor, and resume only once menstruation has normalised.

Key points:

  • Excessive exercise can lead to abnormal menstruation, reduced fertility, and FHA (absence of menstruation).
  • The complications of excess exercise can occur even when you’re eating enough as energy availability is restricted to your reproductive system to fuel the exercise.
  • Allowing rest days and easing into exercise slowly are two ways to ensure your exercise can boost your fertility.
  • It’s important to cease exercise in the short term if you develop FHA and seek medical support.

Take home message

Exercise can increase fertility and your chances of pregnancy by improving the balance of the vital sex hormones involved in your reproductive system, such as LH, FSH, and testosterone.

However, excess exercise has the potential to have the opposite effect and lower your fertility, increasing the risk of developing FHA and other health conditions such as poor bone health.

Like with many health and lifestyle behaviours, the relationship between exercise and fertility exists on what’s known as a ‘u-shaped curve’.

Doing too little, not so great; doing too much, not so great either; somewhere in the middle, perfect.

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