Desire to Have Children and Metabolism: Why Cellular Energy Supply Might Be Important for Fertility

The onset of a pregnancy is a complex biological process in which hormones, metabolism, and cellular functions work closely together. Insulin resistance, mitochondrial processes, and chronic metabolic disorders can affect fertility. Research is increasingly showing how closely metabolic health is linked to egg maturation, sperm quality, and hormonal regulation. But which connections are scientifically proven—and what can couples hoping to conceive learn from this?

Fertility Doesn’t Begin With Ovulation

When it comes to trying to conceive, the focus is often on the menstrual cycle, ovulation, and the right time for intercourse. But the conditions necessary for pregnancy arise at a much more fundamental level: in the cells and the metabolic processes that enable them to function. The human body requires a continuous supply of energy to build cells, produce hormones, and regulate biological processes. The reproductive organs, too, depend on an adequate energy supply and proper hormonal interaction. This is not solely a matter of how much energy is obtained from food. It is also crucial how the body processes nutrients, utilizes glucose, and makes energy available within the cells.

Metabolism is a key component of this system. If it becomes unbalanced, this can affect various organ systems—including the ovaries and testicles. The scientific statement from the American Society for Reproductive Medicine (ASRM) describes how metabolic health and obesity are linked to ovulation, ovarian function, and male fertility. At the same time, the authors emphasize that most women and men with obesity are generally fertile. This means that not every metabolic abnormality leads to infertility. Fertility is influenced by numerous factors, such as age, genetic predisposition, hormonal disorders, and the reproductive health of both partners.

Insulin: A Hormone That Influences Reproduction

Insulin is primarily known as a hormone that regulates blood sugar levels. After a meal, the glucose concentration in the blood rises. Among other things, insulin facilitates the uptake of glucose into certain body cells and helps provide or store energy. However, insulin does not only play a role in carbohydrate metabolism. It is also linked to hormonal processes that are important for reproduction. Insulin resistance is of particular significance in this context. In this condition, certain body cells become less sensitive to insulin. The body then often has to produce more insulin to adequately regulate blood sugar.

Insulin resistance occurs, among other things, in connection with metabolic syndrome and polycystic ovary syndrome (PCOS). In PCOS in particular, the interaction between insulin and sex hormones can influence ovarian function. The international evidence-based 2023 PCOS guideline describes the significance of metabolic changes in this condition. It also points out that direct measurement of insulin resistance using currently available methods has limitations and is not routinely recommended for all affected individuals. For people hoping to conceive, this distinction is important: A suspected metabolic disorder should be medically evaluated rather than drawing premature conclusions based on individual symptoms or a specific body weight.

PCOS: When Metabolism and Hormones Become Unbalanced

Polycystic ovary syndrome (PCOS) is one of the most common hormonal disorders in women of reproductive age. It can be associated with irregular cycles, infrequent or absent ovulation, and elevated androgen levels. Not all affected individuals exhibit the same symptoms. In some women with PCOS, insulin resistance plays an important role. Elevated insulin levels can promote androgen production in the ovaries while simultaneously reducing the production of sex hormone-binding globulin (SHBG) in the liver. This can lead to an increase in the proportion of biologically available androgens.

These hormonal changes can impair follicular development and ovulation. When ovulation occurs only rarely, there are correspondingly fewer opportunities for spontaneous fertilization. The aforementioned international PCOS guideline emphasizes that PCOS should not be diagnosed or assessed based on a single laboratory value alone. PCOS is not synonymous with infertility. Many women with PCOS become pregnant spontaneously or can successfully achieve pregnancy with appropriate treatment. Treatment depends on the individual’s situation. This may include lifestyle adjustments, treatment of accompanying metabolic problems, or targeted medical support for ovulation.

Mitochondria: The Energy Centers of Cells

In addition to metabolism, mitochondria are also increasingly becoming the focus of reproductive research. These cell organelles are often referred to as the cell’s powerhouses because they provide a large portion of the required adenosine triphosphate (ATP). ATP serves as an immediately usable energy source for numerous cellular processes. However, mitochondria are more than just energy suppliers. They are also involved in regulating cellular metabolism, signaling processes, and managing oxidative stress. This is particularly relevant to reproduction because both egg maturation and early embryo development depend on precisely coordinated cellular processes.

A comprehensive review article by Wenying Zhang and Fuju Wu from 2023 examined the relationship between various fertility-related factors and mitochondrial DNA in oocytes. The authors considered, among other things, age, diabetes, obesity, and assisted reproduction. The study describes how changes in mitochondrial DNA may be related to mitochondrial function and the oocyte’s energy supply. It also highlights that multiple factors can simultaneously influence egg cell biology. This research is an important building block for understanding egg cell biology. However, it does not allow for the fertility of an individual woman to be assessed based solely on mitochondrial function. Nor can any generally applicable recommendation for specific dietary supplements be derived from it at this time.

Why Egg Cells Are Particularly Dependent on Properly Functioning Cellular Processes

The maturation of an egg cell is a complex biological process. The cell must not only grow but also correctly organize its chromosomes and create the conditions necessary for potential fertilization. Numerous molecular and cellular mechanisms are involved in these processes. Energy supply plays a crucial role in this context. The aforementioned review article by Zhang and Wu describes how changes in mitochondrial DNA and mitochondrial function may be related to factors that influence egg quality. The authors also discuss the role of age, metabolic disorders, and obesity.

Some of the underlying findings come from experimental studies and animal models. Human studies provide additional insights, but it is difficult to translate individual molecular findings into the actual probability of pregnancy. Egg quality also depends heavily on age and other individual factors. No single metabolic marker can reliably predict whether an egg will be fertilized, an embryo will develop, or a pregnancy will occur. Mitochondria are therefore an exciting area of research, but they are not a simple starting point for specifically and reliably increasing fertility.

Metabolism and Egg Quality: What Is Known About Body Weight and Insulin?

In 2021, the American Society for Reproductive Medicine (ASRM) summarized the findings on obesity and reproduction in its scientific statement Obesity and Reproduction. The review describes associations between obesity and various reproductive factors. These include ovulation disorders, changes in hormonal regulation, and differences in the ovaries’ response to hormonal stimulation during fertility treatments. In women with obesity, changes in the follicular environment were also observed during IVF treatments, including alterations in insulin, inflammatory markers, and free fatty acids. Such changes could play a role in the relationship between metabolic health and egg function.

However, the authors point out that these relationships are complex. Not every woman with a higher body weight has impaired fertility, and a normal body weight does not guarantee unimpeded egg maturation. Equally important is the fact that the effects of weight loss on the actual probability of a live birth are not consistent across all studies. For women with certain types of ovulation disorders, lifestyle interventions can improve the likelihood of ovulation and spontaneous conception. However, this does not mean that every woman should lose weight before undergoing fertility treatment.

It’s Not Just the Woman: Male Fertility Also Depends on Metabolism

Male fertility is often given less attention in the context of metabolic health. Yet the production of functional sperm also requires a finely tuned interplay of hormones, cellular metabolism, and energy supply. A systematic review by Chad Austin Service and colleagues from 2023 evaluated 112 scientific publications on the relationship between obesity, metabolic health, and male fertility. The authors found evidence that obesity, diabetes, and metabolic syndrome may be associated with changes in various sperm parameters and sperm DNA integrity. Hormonal changes also play a role.

Possible mechanisms include altered testosterone regulation, chronic inflammatory processes, oxidative stress, and metabolic disorders. However, the exact significance of these individual mechanisms for the actual probability of conception has not been conclusively clarified in all respects. The authors report that lifestyle interventions, such as physical activity, can improve certain markers of male fertility. Whether such changes reliably lead to more pregnancies or live births, however, must be assessed on a case-by-case basis. A healthy lifestyle can support overall metabolic health. In cases of infertility, therefore, the woman should not be the only one examined. A semen analysis and an appropriate medical evaluation can help identify possible causes on both sides.

Oxidative Stress: When the Balance in Cells Is Disrupted

Reactive oxygen species are produced, among other things, during energy production. In controlled amounts, these molecules perform important functions in cell communication. However, if their levels become too high relative to the body’s antioxidant defense mechanisms, oxidative stress can result. Such a condition can impair cellular components such as proteins, membranes, and DNA. In reproductive medicine, researchers are investigating the role that oxidative stress plays in egg function, early embryo development, and sperm quality. Sperm, in particular, are sensitive to certain forms of oxidative damage because their cell membranes are rich in polyunsaturated fatty acids and their ability to repair DNA damage is limited.

However, oxidative stress is not a uniform pathological condition present in all people struggling with infertility. Nor can it be concluded from this mechanism that taking the highest possible doses of antioxidants improves fertility. The effect of individual dietary supplements depends, among other factors, on the specific substance, the dosage, the individual’s baseline condition, and the quality of the studies.

What Can Support Metabolic Health in Everyday Life?

Those hoping to become pregnant can take some general steps to support their own health and that of their partner. The goal is not to “optimize” the body or to force a pregnancy through “perfect” habits. Above all, routines that can be sustained over the long term are most beneficial:

• Eating a balanced diet: A varied diet that includes vegetables, fruits, whole grains, legumes, nuts, and appropriate protein sources supports overall nutrient intake.
• Exercising regularly: Physical activity can improve insulin sensitivity and contribute to metabolic health. The type and intensity should be tailored to your personal health situation.
• Get enough sleep: Lack of sleep can affect metabolic processes. Regular sleep schedules and sufficient rest are therefore important components of preventive health care.
• Seek treatment for metabolic disorders: If you have diabetes, suspected PCOS, or other hormonal or metabolic abnormalities, it’s important to consult a doctor.
• Avoid smoking and limit alcohol consumption as much as possible: Both are part of general preconception health care.
• Take folic acid early: Women planning to conceive are generally advised to take 400 micrograms of folic acid daily, starting at least four weeks before possible conception and continuing through the end of the first trimester. A different dosage may be necessary if certain risk factors are present.

The recommendation for folic acid from the U.S. Centers for Disease Control and Prevention (CDC) is based in particular on its proven importance in preventing neural tube defects in the developing embryo. It should not be interpreted as evidence that folic acid alone increases the likelihood of conception. These measures do not guarantee pregnancy. However, they can support overall health and, where applicable, help address treatable risk factors.

Dietary Supplements: Not Every Cellular Function Can Be Optimized

Numerous supplements are marketed to those hoping to conceive, claiming to strengthen mitochondria, improve egg quality, or enhance sperm performance. Some of these claims are based on plausible biological mechanisms. However, a plausible mechanism alone does not prove clinical benefit. Similarly, a link between oxidative stress and sperm quality does not imply that high-dose antioxidants increase the likelihood of pregnancy.

For individual supplements, there is evidence of potential benefits in certain groups. However, the body of research varies depending on the substance, diagnosis, and endpoint being studied. Furthermore, an improvement in a laboratory value is not synonymous with a higher live birth rate. Anyone wishing to take dietary supplements should therefore have a professional assess whether there is actually a need for them, whether interactions are possible, and whether the supplements are suitable for use before and during pregnancy. That is why it is important to always seek medical advice before taking any supplements.

Not every case of infertility has a metabolic cause. If pregnancy does not occur, potential causes should be systematically investigated rather than focusing exclusively on diet, exercise, or dietary supplements. A medical evaluation may include, for example, the menstrual cycle and ovulation, hormonal status, the fallopian tubes and uterus, as well as male sperm quality. Which tests are appropriate depends on age, medical history, and how long the couple has been trying to conceive. In cases of known metabolic disorders, diabetes, PCOS, or significantly irregular cycles, early consultation can be particularly helpful. Many medical guidelines recommend a fertility evaluation after twelve months of unsuccessful attempts for women under 35 and as early as six months for women 35 and older. If there are known risk factors or if a woman is over 40, an earlier evaluation may be advisable.

Conclusion: Metabolic Health is a Building Block, Not a Guarantee

Fertility depends on the interplay of many biological processes. Insulin and other hormones influence the function of the reproductive organs, while mitochondria provide the energy for important cellular processes. Metabolic disorders can be associated with changes in egg function, ovulation, and sperm quality.

Research thus provides important insights into the biological prerequisites for pregnancy. However, it also shows how carefully individual findings must be interpreted. Not every observed change leads to a measurable improvement in conception or live birth rates.

For couples hoping to have children, a holistic approach is therefore advisable: a balanced diet, regular exercise, adequate sleep, and treatment of known medical conditions can support overall health. However, these factors do not replace necessary fertility testing and should not be viewed as prerequisites that must be met before seeking medical assistance. The most important finding is this: good metabolic health can create favorable conditions for reproduction. However, it does not guarantee pregnancy—and the absence of pregnancy does not automatically mean that one’s body is malfunctioning.