Does metabolism change with age, and can it affect fertility?

Disclaimer: This article has been sponsored by Novo Nordisk

Top things to know:

• Fertility naturally declines with age, mainly because the number and quality of eggs decrease over time

• Metabolic conditions such as insulin resistance, diabetes, high blood pressure, and polyendocrine metabolic ovarian syndrome (PMOS, formerly PCOS) can affect fertility and pregnancy health—but body weight alone does not determine metabolic health or fertility

• Regular movement, balanced nutrition, adequate sleep, and avoiding tobacco can support overall health while trying to conceive, although no single lifestyle change can guarantee pregnancy

• Consider speaking with a healthcare provider before trying to conceive if you have a chronic condition, take regular medication, have irregular cycles, or have concerns about your fertility

Worldwide, people are having children later in life (1). In many European countries and Canada, the average age at which women have their first child is around 30 (2). This shift may be related to changes in the economy, technology, cultural norms, education levels, and health factors (1).  

Having a baby later in life brings unique considerations. Fertility naturally declines with age, mainly because the number and quality of eggs decrease. Metabolic health can also influence ovulation, fertility, and pregnancy health, although it is only one part of the picture.

What is metabolic health? 

Metabolism is the sum of all the processes in the body that work together to make energy, keeping you alive and active (3). Metabolic health refers more broadly to how well the body regulates blood sugar, blood pressure, blood fats, and other processes that affect long-term health (4). It's sometimes described as the absence of metabolic syndrome (5). 

Metabolic syndrome is a group of conditions that together raise the risk of cardiovascular disease, stroke, and other health conditions (6).  It is usually diagnosed when someone has at least three of the following (6):

• A large waist circumference

• High blood pressure

• High blood sugar

• High triglycerides

• Low high-density lipoprotein (HDL) cholesterol

Metabolic syndrome is common. Some studies estimate that it affects around 1 in 3 women (7).

Can metabolic health change with age?

Several changes that can affect metabolic health become more common with age, but they do not happen in the same way—or at the same age—for everyone.

Starting in your 30s, muscle mass gradually decreases. Muscle burns more calories than adipose tissue (fat). When someone has more fat mass than muscle mass, they will burn fewer calories at rest. This is known as a decreased basal metabolic rate (8). 

Insulin sensitivity may also decrease with age. Insulin resistance happens when muscle, fat, and liver cells do not respond to insulin as effectively. The body may then produce more insulin to help keep blood sugar within a healthy range. Over time, insulin resistance can contribute to high blood sugar, type 2 diabetes, and metabolic syndrome. Higher body fat, lack of exercise, poor nutrition, and use of certain medications are also risk factors for insulin resistance (9). 

Visceral fat is fat stored around the abdominal organs. Levels may increase with age and are associated with cardiovascular and metabolic conditions (10-12). Research has also found associations between visceral fat and some fertility problems, but this does not mean visceral fat alone causes infertility (13).

Is metabolic health the same as body weight?

No. Metabolic health and body weight are related, but they are not the same. 

A large waist circumference is one possible feature of metabolic syndrome (6). It is often associated with poor health outcomes (14).

However, body weight alone cannot show how much muscle or fat someone has, where body fat is stored, or how well their body regulates blood sugar, blood pressure, and cholesterol.

It is one of many measures that may contribute to an overall picture of health. 

How does age affect fertility?

Fertility is generally highest from the late teens through the 20s. It begins to decline around age 30, with a faster decline from the mid-30s onward (15). Pregnancy in the 40s is still possible, but becoming pregnant may take longer, and the chance of pregnancy complications increases with age (15). 

Egg quantity decreases with age 

You are born with the most ovarian follicles you will ever have—around 1 to 2 million. Each of these follicles is home to an immature egg. Follicles are continuously lost through a natural process called atresia. By puberty, fewer than 500,000 follicles typically remain, and the number continues to decline until menopause (16). 

With each menstrual cycle, a dominant follicle matures and releases an egg. This is called ovulation. If sperm fertilizes the egg, the resulting embryo may implant in the uterus and develop into a pregnancy.

During peak reproductive years, a healthy couple may have around a 1 in 4 chance of pregnancy in a given cycle. By age 40, the chance is closer to 1 in 10 (15). 

Egg quality also decreases with age

Not only do you have fewer follicles with age, but the quality also decreases. The remaining eggs are more likely to contain chromosomal changes. This increases the chance that an embryo will not implant, that a pregnancy will end in miscarriage, or that a baby will have certain chromosomal conditions (15). 

The risk of pregnancy loss increases with age. Estimates vary between studies and populations, but one source reports risks of approximately (17): 

• 1 in 5 pregnancies at age 35 

• 2 in 5 pregnancies at age 40

• 4 in 5 pregnancies at age 45

Multiple pregnancy, such as twins, also becomes somewhat more common with age. This may partly relate to age-related changes in ovulation (15). Fertility treatment is another important contributor to multiple pregnancy rates.

Chronic health conditions are more common with age

People who are pregnant later in life are more likely to have pre-existing health conditions, such as high blood pressure, diabetes, kidney disease, cardiovascular disease, or autoimmune conditions. This can put them at 2 to 3 times higher risk of pregnancy-related complications (18). 

First-time mothers who are older than 35 are also much more likely to be diagnosed with pregnancy-related complications like gestational hypertension, preeclampsia, and gestational diabetes (18). Age is only one factor, however, and individual risk depends on overall health and pregnancy history.

How is metabolic health connected to fertility?

Studies have shown that metabolic health can influence ovulation, fertility, and pregnancy outcomes. The relationship is complex and can work in both directions. Some hormonal conditions affect both fertility and metabolism. Metabolic health is also influenced by genetics, medications, access to healthcare, social and environmental conditions, and health behaviors.

Body size and fat distribution

Body mass index (BMI) is a ratio of weight to height. A BMI of 30 kg/m² or above is commonly categorized as obesity. BMI does not measure body composition, fat distribution, metabolic health, or fertility, and it cannot capture an individual’s overall health. Measurements such as waist circumference may sometimes provide additional information about metabolic risk (6,19).

Higher levels of body fat can be associated with changes in reproductive hormones, insulin resistance, and inflammation. In some people, these changes may interfere with ovulation or make pregnancy less likely (19,20). 

However, people across the weight spectrum can be metabolically healthy or develop metabolic conditions, and many people with obesity become pregnant without fertility treatment.

It is difficult to separate the effect of body size from other influences, including age, underlying conditions, medications, nutrition, physical activity, environmental exposures, and access to care (19).

Insulin resistance

Insulin is important for ovarian function. Higher insulin levels cause problems with the development of ovarian follicles. Instead of one dominant follicle developing and releasing an egg, insulin can recruit multiple follicles to partially develop. This can interfere with ovulation (19). 

People with metabolic syndrome often have multiple features that work together to increase health risks. People with high insulin levels often also have abdominal obesity. Both high body fat and high insulin can increase the level of free fatty acids in the blood (20). Free fatty acids can damage body tissues, including the ovaries (20).

Insulin can also reduce levels of sex hormone-binding globulin. This may increase the amount of testosterone available in the body and disrupt ovulation in some people (21). 

Inflammation

Inflammation is important for the immune system to protect and heal the body. However, chronic inflammation can contribute to tissue damage. This can increase the risk of chronic health conditions and poor health outcomes (22). 

Factors like poor diet, smoking, extreme exercise, and lack of sleep can worsen inflammation in the body (22). Obesity can also increase inflammation, as fat cells release pro-inflammatory chemicals in the body (21,22). 

Inflammation is closely linked to insulin resistance. It can disrupt the reproductive hormones in your body, including testosterone (22). 

Higher levels of inflammation may interfere with the development of the uterine lining. This might affect the ability of a pregnancy to implant in the uterus. Inflammation can also increase the risk of problems like heavy menstrual bleeding, period pain, and endometriosis (22).

PMOS, formerly PCOS

Polyendocrine metabolic ovarian syndrome (PMOS) is the new name for the condition previously called polycystic ovary syndrome (PCOS). This name change reflects what has been known about this condition for a long time. 

PMOS is a complicated disorder that involves more than just cysts of the ovaries. PMOS can involve differences in insulin and androgen hormones such as testosterone. These differences can affect many organs and body systems (23).

People with PMOS are more likely to have metabolic risk factors or conditions, including (23):

• Insulin resistance or abnormal blood sugar

• Obesity

• High cholesterol

• High blood pressure

• Cardiovascular disease 

They are also more likely to experience irregular menstrual cycles, difficulty ovulating, and infertility (23). Not everyone with PMOS has the same symptoms or metabolic risks. 

People who become pregnant with PMOS are more likely to have complications during pregnancy, including (24): 

• Miscarriage

• Gestational diabetes

• High blood pressure disorders of pregnancy, like preeclampsia

• Cesarean birth

Pregnancy outcomes

Poor metabolic health is linked to negative pregnancy outcomes. 

Metabolic conditions like abnormal blood sugar and lipid control are associated with some adverse pregnancy outcomes (25). The specific risk depends on the condition, how well it is managed, and other individual factors.

Metabolic syndrome seems to increase the risk of infertility, but the interaction is complicated. People with infertility may have hormonal changes that disrupt metabolism (19). More research is needed on how these conditions interact.

Does metabolic health affect sperm health? 

Yes, obesity and metabolic syndrome are associated with lower sperm count and motility, as well as changes in sperm morphology and reproductive hormones (26). Higher body fat can also increase the temperature around the testes and is associated with insulin resistance and inflammation.

Can supporting metabolic health improve fertility?

Age-related changes in the ovaries cannot be prevented through lifestyle changes. However, looking after your metabolic and overall health can support wellbeing before and during pregnancy. For people with conditions that affect ovulation, such as PMOS or diabetes, appropriate treatment may also support reproductive health.

No single behavior, food, supplement, or body-weight change can guarantee pregnancy. If you have concerns about fertility or a metabolic condition, a healthcare provider can help identify which changes or treatments are appropriate for you.

Regular physical activity

Exercise can reduce the risk for many chronic illnesses, like heart disease and cancer. Regular moderate-to-vigorous intensity exercise is recommended for most people to improve overall health (27). This may include activities like walking, jogging, swimming, biking, or weightlifting. The best exercise regimen is one that you enjoy and will do consistently.

Exercise can support positive mental health as well as physical health. During pregnancy, regular exercise is also linked to health benefits for both mother and fetus (27). 

For most healthy women trying to get pregnant, regular moderate or vigorous exercise will not negatively impact fertility. However, it is important to eat enough calories to balance the energy that you burn during activity (27).

For people with metabolic conditions known to impact fertility, like PMOS, regular vigorous exercise and weight training may help improve fertility. It has benefits regardless of weight loss (27). 

Balanced nutrition

There is no single diet recommended for optimal fertility. Some research suggests fertility improves when diets are rich in (28,29):

• Whole grains 

• Vegetables

• Fruits 

• Plant-based proteins 

• Omega-3 fatty acids

• Full-fat dairy 

• Soy isoflavones 

• Vitamins and nutrients (like folic acid) 

Certain diets prioritize these types of foods more than others; for example, the Mediterranean diet tends to include fruits, vegetables, legumes, whole grains, olive oil, and nuts while limiting red meats and added sugars (29). 

If you could become pregnant, experts generally recommend a supplement containing at least 400 micrograms of folic acid each day before conception and during early pregnancy (28). 

Sleep

Adequate sleep is important for overall health. 

Poor sleep is linked to several metabolic health conditions, including (30):  

• Obesity

• High blood pressure

• Type 2 diabetes

• Cardiovascular disease

• Non-alcoholic fatty liver disease

• Metabolic syndrome

Sleep seems closely linked to blood sugar control in the body. Research shows that people who get less sleep are more likely to show insulin resistance. Poor sleep can also increase appetite by altering hormones like ghrelin and leptin, which may lead to overeating and weight gain (30).

Lack of sleep can increase levels of the stress hormone cortisol. It can cause activation of the fight-or-flight system in the body that affects heart rate, blood pressure, and heart rate variability (30). 

Poor sleep is also linked to higher levels of inflammation, which can cause damage to blood vessels and increase cardiovascular risk (30). 

People who regularly get 7 to 9 hours of sleep seem to have the best health outcomes (30). You can improve your sleep hygiene by (30):

• Keeping a cool, dark sleeping space

• Avoiding heavy meals, alcohol, and caffeine close to bedtime

• Avoiding screen exposure close to bedtime

Stress management

Chronic stress is linked to chemical changes in the body that increase the risk of metabolic conditions and infertility (31). Mindfulness practice and cognitive behavioral therapy are practices that might help someone manage stress and improve overall well-being (32). 

A strong social support network can also help manage stress while trying to become pregnant. This might include time with family or friends. It could also include support groups of people going through similar experiences (32). The important thing is to know that you are not alone, no matter what you are going through.

Stopping tobacco and nicotine use

It is best to stop using cigarettes and other tobacco products before trying to become pregnant (15). 

Cigarette smoking is linked to a higher risk of heart disease, stroke, high cholesterol, high blood pressure, and heart attack (33). 

Tobacco use can decrease ovarian reserve, or the number of eggs someone has remaining in their ovaries. It can also negatively impact egg quality, leading to increased risk of miscarriage and birth defects (34). 

Some research suggests that e-cigarettes and other vaping products also increase the risk of obesity, high blood sugar, and high blood pressure (35). More research is needed.  

Managing chronic conditions and medications

Experts recommend good control of chronic health conditions before pregnancy. Conditions such as diabetes, high blood pressure, thyroid disease, and kidney disease may need closer monitoring or treatment changes (36). 

Review all prescription medicines, over-the-counter medicines, and supplements with a healthcare provider before trying to conceive. Do not stop prescribed medication without medical advice. This is particularly important for medicines that are not recommended during pregnancy, including some GLP-1 receptor agonists used for diabetes or weight management (37).

When should you seek medical advice?

If you hope to become pregnant within the next year, a preconception appointment can help you review nutrition, activity, sleep, medications, vaccinations, substance use, and chronic conditions (15,36).

Consider reaching out to your healthcare provider about a fertility evaluation if you (36,38):

• Are younger than 35 and have been trying to conceive for 12 months

• Are 35 years or older and have been trying for 6 months

• Are 40 years or older when you start trying 

• Have irregular or absent periods, a condition known to affect fertility, a history of chemotherapy or pelvic radiation, or another reason for concern at any age

When a partner is contributing sperm, fertility evaluation should generally include both partners.

What tests might be recommended before pregnancy?

Most people don’t need extensive fertility or metabolic testing done before trying to get pregnant. Your OB/GYN may recommend screenings for sexually transmitted infections (STIs) and checking immunity or vaccination status. They may also recommend genetic testing to see if you or your partner are carriers for genetic conditions (15). 

If you have risk factors for thyroid conditions, diabetes, or high cholesterol, your healthcare provider may recommend screening (38,39). 

For people with irregular periods, people who are over 40, or people undergoing infertility evaluation, your healthcare provider may recommend additional hormone testing. This can include testing thyroid, prolactin, and progesterone levels. They might also recommend urine ovulation tests, which detect the surge in luteinizing hormone (LH) that occurs with ovulation (38,40)

What should you track if you're trying to conceive?

You can track your cycle with Clue Conceive to notice patterns in your cycle and fertility signs. 

Changes in cycle length or regularity can give you an idea about your own hormonal or metabolic health. Seek advice if your periods are consistently very irregular or absent, or if you notice a significant change from your usual pattern.

It may be helpful to track fertility awareness signs like discharge changes and basal body temperature. Clear, slippery cervical mucus that looks like egg whites is often seen in the days before ovulation (40). A sustained rise in basal body temperature can suggest that ovulation has already happened, but it does not precisely predict ovulation in advance.

You may also choose to track sleep, exercise, energy, mood, or other experiences that matter to you. These trends can support conversations with a healthcare provider, but cannot diagnose metabolic health or confirm fertility. Tracking body weight is optional and may not be helpful for everyone.

FAQs

What is metabolic health? 

Metabolic health refers to how well the body is able to produce and use energy to maintain its energy balance (4). It is sometimes defined as the absence of metabolic syndrome (5). People with metabolic syndrome have some combination of large waist circumference, high blood pressure, high blood sugar, high triglycerides, and low HDL cholesterol (6). 

Can improving metabolic health increase my chances of getting pregnant?

Changes in diet, activity, sleep, and stress management are helpful for optimizing your overall and metabolic health. For some people with a condition that affects ovulation—such as PMOS or poorly controlled diabetes—appropriate treatment may also support reproductive health.

However, evidence that any single lifestyle change improves pregnancy or live-birth rates is limited. Weight loss is not necessary or appropriate for everyone trying to conceive. A healthcare provider can assess whether a metabolic condition may be affecting your fertility and discuss suitable treatment.

Does age affect fertility?

Yes, fertility declines with age (15). The number of follicles in the ovaries decreases naturally from birth until menopause (16). Egg quality also decreases with age, increasing the chance of miscarriage and certain chromosomal conditions (16). Age-related ovarian changes cannot be prevented through diet, exercise, sleep, or body-weight changes.

How are insulin resistance and fertility connected?

Insulin is involved in ovarian function as well as blood-sugar control. Insulin resistance can lead to higher insulin levels, which may affect reproductive hormones and interfere with ovulation, particularly in people with PMOS (19,21). However, insulin resistance does not always cause infertility, and fertility problems can have many causes.