Metabolic health is sexy. Not just because it’s endlessly fascinating and getting a lot of (well-deserved) attention right now, but because it literally determines how people function and feel before and during sex—and even how a person feels about sex.
Why does this matter? About 40 percent of women of reproductive age globally experience some type of sexual dysfunction, with desire or orgasm. The prevalence increases to as much as 85 percent for those who’ve reached menopause. More than half (52 percent) of men over 40 also have concerns, often with erectile dysfunction (ED). But ED also affects up to a quarter of guys under 40.
Researchers argue that sexual well-being is key to overall health. But our sexual health also has ramifications for fertility. (Spoiler alert: next month’s newsletter is about metabolic health and fertility.)
What’s the metabolic connection? The way the body produces and manages energy (aka, our metabolism) impacts blood flow (key to an erection and clitoral and vaginal arousal), sex hormone levels (like testosterone and estrogen), and our psychology (mood, motivation, and reward), all of which impact sexual function and the experience of sex. So if you happen to care about sex, sexual pleasure, or fertility … it’s time to learn about metabolism.
88% of American adults are metabolically dysfunctional, meaning that our diets, lifestyles, and exposures lead our cells to struggle with the basic process of making energy from food to power our bodies and minds. And what goes largely unrecognized is that this rampant metabolic dysfunction affects our ability to become aroused, experience an orgasm, and make a baby. And it makes sense—when the body’s core physiology is hijacked by the constellation of factors that lead to metabolic dysfunction (e.g., micronutrient depleted ultra-processed diets, inadequate sleep, sedentary behavior, chronic low-grade stress and unprocessed trauma, microbiome issues, lack of adequate sunlight exposure, and environmental toxin overload), it feeds into widespread problems in all parts of the body.
Here are three main ways metabolic health can impact sexual function.
1. Blood Flow
- Blood flow to sex organs is critical: Sexual arousal and climax require proper blood flow, and blood flow depends on metabolic health because both blood sugar and insulin impact blood vessel diameter. Research now shows that erectile dysfunction may be the first clinical sign of insulin resistance and atherosclerosis (damage, plaque build-up, and potential blockage of blood vessels). Physicians like Levels advisor Sara Gottfried, MD, who specializes in metabolic and sexual health, say: “Erectile dysfunction is atherosclerosis of the penile artery until proven otherwise.” Dr. Gottfried interprets ED as a neon sign that the person needs a complete cardiometabolic evaluation. It includes (at a bare minimum) thorough metabolic lab testing, blood pressure assessment, and anthropometric measurements like waist-to-hip ratio (all three of which factor into the definition of metabolic syndrome).Of course, hormonal, neurological, and psychological mechanisms are also critically involved, but good blood flow is table stakes for erection.Regardless of what sexual organs you have, erectile tissue activity is part of sexual function. Although only a small portion of the clitoris (the glans clitoris) is visible, it’s really an upside-down Y-shaped gland, with most of it internal. Spongy tissues called the corpora cavernosa branch off the clitoris, as does the vestibular bulb, all of which swell with blood as part of the arousal and orgasm process—twice as many women with Type 2 diabetes experience sexual dysfunction as compared to women without.
- Blood to the nerves matters, too: It’s not just blood flow to the erectile tissue that’s important, but also the blood that supplies the peripheral nerves that control sexual function, like the pelvic ganglia. In rat models, diabetes induction leads to 50% reduction of blood flow to these nerves in just one week, and over the long term, this low oxygen delivery to nerves can cause permanent damage.
- The brain plays a role in blood flow: In the process of arousal, visual, mental, and physical stimulation sets off excitatory signals in the brain. The central nervous system then signals the release of nitric oxide—a potent dilator of blood vessels—and acetylcholine, a neurotransmitter. These chemicals cause arteries to relax and become engorged with blood. The engorgement causes the penis or the clitoris to become erect. Insulin resistance and diabetes affect the parts of the brain that set off this process, leading to dysfunction in how nitric oxide is synthesized and released. Nitric oxide is also responsible for relaxing the vaginal wall, causing dilation, and enhancing lubrication—all aspects of sexual function and pleasure for women. Some research shows a link between women with impaired fasting glucose and difficulty with natural lubrication.
- Advanced glycation end products: High glucose levels may also impair vascular function and nitric oxide levels through advanced glycation end products (AGEs). AGEs form when glucose reacts with and sticks to proteins and fats. Hyperglycemia and resultant AGEs ultimately contribute to atherosclerosis and overgrowth of blood vessel tissue, both of which can cause constriction of blood vessels that leads to blockage.
- The role of insulin: Insulin plays a role here as well. Under normal circumstances, insulin promotes the dilation of blood vessels. But in the setting of insulin resistance and resultant hyperinsulinemia (the body compensating with increased insulin production), the blood vessels are less able to respond to the insulin signal. Research shows these processes can occur in the early stages of insulin resistance.
- Sex hormones also dictate blood flow: Hormones can also affect nitric oxide levels. For instance, testosterone and estradiol are both known to be inducers of nitric oxide synthase, and low levels of both can lead to low nitric oxide levels. Of note, testosterone deficiency is present in up to 50% of men with Type 2 diabetes, with a strong bidirectional relationship between insulin resistance and low testosterone levels.
High blood sugar and insulin resistance can significantly contribute to sex hormone imbalances in both men and women, and insulin has a direct effect on many of the enzymes involved in the production and conversion of sex hormones in the body, as well as impacting the levels of sex hormone-binding globulin, which transports sex hormones in the bloodstream.
Both testosterone and estrogen decrease for women after menopause, compounding issues with sexual function. For men, sex hormones also naturally decline with age and appear to be falling more rapidly over the past several decades than historically expected, possibly due to environmental factors like increased toxin exposure, as well as excess fat tissue. “Fat tissue in men is uniquely capable of behaving like ovaries, turning testosterone into estrogens,” notes Levels advisor Dr. Ben Bikman, author of Why We Get Sick. For all genders, low testosterone levels are associated with lower libido. In men, weight loss, resistance and aerobic exercise, and optimal sleep and stress management have been show to positively impact testosterone levels.
Levels advisor Dr. Sara Gottfried notes: “The American College of Physicians (ACP) defines low testosterone as <320 ng/dL combined with signs and symptoms, including sexual dysfunction, decreases in energy and muscle mass, mood disturbances, changes in bone mineral density, cardiovascular disease, and loss of body hair. While there is still debate about the appropriate cut-off, serum levels of 200-400 ng/dL are considered borderline. The ACP and the American Urological Association recommend that clinicians inform testosterone-deficient patients that it is an independent risk factor for cardiovascular disease. Treatment can improve measures of diabetes, energy, fatigue, lipid profiles, and quality of life.” Simply put, low testosterone appears to be closely related to cardiometabolic disease and insulin resistance, and these processes also feed back into further disrupting testosterone.
Indeed, insulin resistance impacts sex hormones by disrupting the hypothalamic-pituitary-gonadal (HPG) axis. More research is needed on the exact mechanisms, but higher levels of leptin and proinflammatory cytokines are likely culprits. The hypothalamus produces and secretes gonadotropin-releasing hormone (GnRH). GnRH then stimulates the pituitary gland to produce and secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In men, LH activates testosterone production in the testicles. In women, FSH stimulates aromatization of androgens in the ovaries’ theca cells to produce estradiol (a type of estrogen). If the HPA axis is disturbed by insulin resistance, it can throw everything off.
Hormones are complex, but one crucial point to remember: hormone balance is a function of many different systems of the body working in concert, and much of what keeps the hormone symphony in harmony are similar to factors that lead to metabolic health. Hormone health—and specific sex hormone balance—involves:
- The production of the hormone (enzymatic processes, many of which are affected by insulin levels)
- The transport of the hormone via its binding to carrier proteins like sex hormone-binding globulin (which is directly impacted by insulin levels)
- The sensitivity of cells to the hormone (insulin has an impact on estrogen receptors)
- The detoxification and excretion of the hormone (which involves the liver and gut, both critical organs in metabolic health)
At all levels, insulin sensitivity helps with the proper functioning of these processes in the hormone’s life cycle. For instance, to have optimally balanced estrogen levels, estrogen must be routinely metabolized by the liver (via two phases of hormone detoxification) and then excreted in the stool. Therefore, diet and lifestyle habits that support liver health and optimal gut and bowel function are critical for estrogen balance and essential for optimal metabolic health.
What helps with both hormone balance and insulin sensitivity? Nutrient-dense whole foods (to support enzymatic processes, hormone synthesis, cell membrane integrity, and endothelial function); fiber and probiotic foods to support gut function; optimal liver functioning (meaning avoid fatty liver disease, of which fructose and alcohol consumption is a major culprit); and avoidance of environmental toxins that disrupt both hormone activity and metabolism.
3. Mood and Motivation
Hormones and metabolism can also impact our mood and energy, changing our fundamental desire to engage in sexual activity.
- Insulin resistance is related to mitochondrial dysfunction in the brain, which may lead to depression, anxiety, neurodegenerative diseases, and other mental health issues that can also affect energy, desire, and sexual motivation.
- And, on a basic level, when we feel healthy and are taking positive approaches to our health, such as engaging in physical activity or eating a healthy diet, we boost our sex drive. Conversely, libido and sexual function can plummet when we’re having health issues.
- Lastly, let’s not forget dopamine. Dopamine is involved in anticipation of reward and motivation pathways in the brain. Various substances and activities can stimulate it, including sugar, sex, alcohol, digital technology (hello, Instagram, Netflix, Slack, porn), opioids, gambling, and more. Repeated exposure or “hits” of dopamine can alter our dopamine threshold, making it more challenging to get pleasure the next time; this ratchets up the stimulation needed to achieve reward and pleasure (simplistically, this is the basis of addiction). In my mind, this is critical to understand as we examine how motivated (or apathetic) individuals feel to pursue sex and how much pleasure they can get from it. Is it possible that the multifarious dependencies we have in our modern Western world (aka sugar, alcohol, our phones) are changing the reward set point such that it’s harder to get as much pleasure from sex?Dr. Andrew Huberman explains it well in an incredible recent podcast episode: “Often, we are feeling good because we are layering in different aspects of life and doing things that increase our dopamine and getting those peaks, but afterward the drop in baseline [dopamine] occurs, and it always takes a little while to get back to our stable baseline. We really all have a sort of dopamine set point, and if we continue to indulge in the same behaviors or even different behaviors that increase our dopamine in big peaks over and over again, we won’t experience the same level of joy from those behaviors or from anything at all. Even for people who aren’t addicted, even for people who don’t have an attachment to any specific substance or behavior, this drop below baseline after any peak in dopamine is substantial, and it governs whether or not we are going to feel motivated to continue to pursue other things.”Given the realities of the human brain’s reward circuitry, less can sometimes be more. It is curious to examine whether restricting some of our multifaceted dopamine hits (i.e., sugar, Instagram, alcohol) and getting off the dopamine treadmill could help us shift our neurochemical baseline to one where we can experience more reward and motivation at lower thresholds of stimulation. (For more on this topic, check out one of my favorite books, Hacking of the American Mind, by Dr. Rob Lustig.)
The Bottom Line
Our metabolic health has massive implications for our sexual health. High blood sugar and insulin resistance can contribute to sexual dysfunction, disinterest, or a lack of enjoyment, yet few doctors will clue you into this link. Yet, sexual health is a crucial component of overall health and well-being.
You can gain a snapshot of your metabolic health status by looking at your metabolic blood tests. We have a guide to interpreting your cholesterol panel and one on understanding glucose levels that will help.
These tests will also be informative if you are concerned about fertility. Keep an eye out for my next newsletter, which tackles the important topic of how fertility intersects with metabolic health.