Adipose tissue expresses aromatase, which converts androgens to estrogens. In obesity, aromatase activity in adipose tissue contributes to increased estrogen production, especially estradiol.

In males, testes produce only around 20% of circulating estrogens, while **the remainder comes from local production by adipose, brain, skin and bone**, which convert testosterone to estrogen via aromatase.[9] This means that adipose (fat) tissue is a major site of estrogen production in men. Lower amounts of adipose tissue therefore reduce peripheral aromatization capacity and tend to lower, not raise, circulating estrogen levels when testosterone is not increased.

Total and free testosterone and sex hormone binding globulin concentrations decreased, whereas total and free estradiol increased with increasing BMI, waist circumference, and percent body fat (all P-trend <0.05). Lower total and free estradiol, and androstanedial glucuronide concentrations were observed among men with lower body fatness. These data suggest that higher body fatness is associated with higher estradiol, while leanness/low body fat is associated with lower estradiol in men.

Aromatase is expressed in adipose tissue, and increased adipose mass can increase the conversion of testosterone to estradiol. This mechanism is commonly discussed in the context of obesity-related changes in sex hormones.

Total and free testosterone and sex hormone binding globulin concentrations decreased, whereas total and free estradiol increased with increasing BMI, waist circumference, and percent body fat (all P-trend <0.05). However, in the fully adjusted model (Model 3), total estradiol statistically significantly increased with increasing BMI (Table 2) and waist circumference (Table 3). These data indicate that higher body fatness in US men is associated with *higher* estradiol, while lower BMI is in the lower estradiol group.

After adjustment for age, total E2 levels were significantly and positively associated with BMI (Age-adjusted: b: 0.20, SE: 0.088; p=0.0225). In addition total and free E2 levels were significantly higher in obese than non obese men. Total E2 levels were 9.2 ± 6.2 pmol/L in non obese and 10.1 ± 6.2 pmol/L in obese older men (age-adjusted p value=0.0479). Total E2 levels were significantly and positively associated with BMI, independent of age, consistent with higher estradiol at higher BMI rather than in underweight men.

BMI was positively associated with estradiol levels in most quantiles (≤80th) after adjustment for age (all P < 0.05). Quantile regression between BMI and estradiol indicated that BMI was positively associated with estradiol levels in most quantiles (excluding the 80th and 90th quantiles). Our study suggested that BMI was one of the influencing factors of testosterone and estradiol, with higher BMI linked to higher estradiol, not lower BMI causing excess estradiol.

In men, higher body fat is associated with increased aromatization of androgens to estrogens. The common pattern is obesity-related elevation of estradiol, not low body weight causing excess estrogen.

In multivariable-adjusted analyses, we observed statistically significant positive correlations between E2 and weight (r = .14), BMI (r = .13), and hip circumference (r = .12) and between FE2 and percentage total (r = .13) and trunk (r = .15) fat mass, and anthropometric measures including weight, BMI, and waist and hip circumference (r = .15–.20). These findings indicate that higher estradiol (E2) in men is associated with higher BMI and fat mass, not with being underweight.

Obesity is associated with increased aromatase activity in adipose tissue, which can raise estrogen levels in men and contribute to gynecomastia.

In males with increasing obesity there is increased aromatase activity, which irreversibly converts testosterone to estradiol resulting in decreased testosterone and elevated estrogen levels. This review describes the hypogonadal–estrogen receptor relationship in obese men: increasing body fat is linked to more aromatization of testosterone to estradiol and relative hyperestrogenemia. The mechanism described is obesity-related; there is no suggestion that underweight men develop excess estrogen from low body fat.

Testosterone can undergo conversion to 17β-estradiol by the enzyme aromatase… Estradiol deficiency clearly predisposes males to increased adiposity and metabolic dysregulation. Obesity in men has been associated with hyperestrogenemia… obesity in men is often characterized by a profile of low circulating androgens but elevated levels of circulating estrone and 17β-estradiol. Thus, increased peripheral aromatization of testosterone in obese men may lead to enhanced central estradiol signaling that suppresses gonadotropin production and contributes to a sustained state of hypogonadotropic hypogonadism. The chapter discusses estradiol’s role in body weight regulation but does not state that low body weight causes excess estradiol; rather, it links obesity with higher estradiol and relative estrogen excess.

Overall, respective free estradiol medians were 0.82, 0.72, and 0.64 pg/mL in NHANES III and 0.67, 0.61, and 0.47 pg/mL in continuous NHANES. In nonsmoking, lean men without comorbidities, respective free estradiol medians were 0.64, 0.67, and 0.62 pg/mL in NHANES III and 0.58, 0.42, and 0.40 pg/mL continuous NHANES. For lean men without comorbidities, free estradiol concentrations were slightly lower than for all men in both NHANES III and NHANES 1999 to 2004, indicating lean/low-BMI men do not have excess estradiol.

In men with obesity, increased adipose tissue leads to increased aromatization of testosterone to estradiol. This supports the mechanism that higher fat mass, not low weight, is associated with elevated estrogen.

In men, approximately 15% of circulating estrogens are derived from testicular production, whereas the remainder is produced in peripheral tissues through conversion of androgens by the enzyme aromatase (ARO)… Adipose tissue is a major source of estrogen production in men, and it is hypothesized that increased aromatase activity in adipose tissue contributes to lower testosterone and hyperestrogenemia in men with obesity. Our study did show a negative association between circulating testosterone and several obesity markers, including BMI, as well as lower testosterone/E2, which are consistent with findings that obesity is associated with reduced total testosterone and an elevated E2/testosterone ratio. This work describes adipose tissue as a key source of estrogen in men, with obesity (higher fat mass) linked to relative hyperestrogenemia; it implies that very low fat mass would tend toward *lower*, not higher, estrogen.

The testosterone/estradiol ratio was significantly reduced in the high BMI group as compared to the low BMI group (17 +/- 4 vs. 12 +/- 3; p < 0.05). This indicates that men with higher body weight have relatively more estradiol compared with testosterone than men with lower body weight. The study’s comparison of low vs. high BMI groups shows that excess weight, not underweight, is associated with a lower T/E2 ratio consistent with relatively higher estrogen in heavier men.

Studies in the past have found that **estrogen concentrations are elevated in obese men as compared with lean men and that estradiol concentrations correlate positively with BMI**.[3] In men with subnormal free testosterone concentrations, mean estradiol concentration was **significantly lower** than in men with normal free testosterone concentrations.[3] The authors state: "We have not found any study showing elevated estradiol concentrations in men with subnormal testosterone concentrations".[3]

Though there was a relative increase of 10% in the levels of estradiol in obese men compared to controls (BMI<25), this difference was not significant. We found similar relative changes in estradiol levels, with higher levels in obese men by 10.3% and lower levels in overweight men by 9.2% compared to men with BMI from 18–25. Overall, obesity in men has been associated with hyperestrogenemia, and excessive estradiol exposure has been postulated to play an exacerbating role in the progression of obesity and attendant metabolic dysregulation, linking higher BMI with higher estrogen rather than underweight with excess estrogen.

Aromatase in fat tissue converts testosterone to estradiol. This is one reason men with obesity can develop higher estrogen levels and gynecomastia.

Our results demonstrated that the decrease in BMI and WC led to a substantial improvement in TT and FT levels and a statistically significant decrease in E2 levels (Table 5). Weight loss was associated with lower estradiol (E2) and higher testosterone in obese men, suggesting that higher body weight contributes to elevated estradiol, and reducing BMI lowers estradiol rather than low BMI causing excess estradiol.

Obesity can raise estrogen levels, but some research suggests that it does not raise them above the normal range. A rare cause of high estrogen is aromatase excess syndrome… In this condition, the body makes too much of an enzyme (called aromatase) that converts testosterone into estrogen. Because obesity raises estrogen levels, maintaining a healthy weight can help prevent male breast cancer. This patient-focused summary lists causes of *high* estrogen in men (obesity, aromatase excess, tumors, liver disease) and does not mention underweight as a cause of excess estrogen.

High estrogen in men can be raised by certain health conditions such as **weight gain or obesity**, some tumors, diseases that affect the liver, and conditions that affect hormone balances such as hypogonadism.[4] The article does not list underweight or low body weight as a cause of high estrogen; instead, obesity and weight gain are emphasized as contributors to increased estrogen.[4]

Excess adipose tissue increases aromatase-mediated conversion of androgens to estrogens. Underweight status is not listed as a cause of high estrogen in men; rather, malnutrition is more often linked to hypogonadism and low testosterone.

There was no significant difference between the groups in terms of serum follicle stimulating hormone, luteinizing hormone, estradiol, prolactin, semen volume, sperm concentration, total sperm count, and progressive and total motility. In this study of BMI and reproductive hormones in infertile males, estradiol levels did not differ significantly between normal, overweight, and obese groups, suggesting no clear excess of estradiol specifically linked to low BMI.

The principal mechanism for elevated estradiol in men is aromatization in adipose tissue, which rises with greater fat mass. Weight loss can reduce estradiol in men who are overweight or obese.

Yes. Adipose (fat) tissue is rich in aromatase — the enzyme that converts testosterone to estradiol. Men with more body fat have greater aromatase activity and typically higher estrogen levels. Extreme leanness or low body fat — since aromatization occurs in fat tissue, very low body fat reduces estrogen conversion. High total estrogens = excess aromatization, exogenous androgens (TRT, DHEA), obesity, liver disease, or estrogen-secreting tumor. This clinical explainer states that extreme leanness in men reduces estrogen conversion, whereas obesity and aromatase excess increase estrogen.

Clinical discussions of gynecomastia emphasize obesity, medications, liver disease, and hypogonadism as causes of estrogen-androgen imbalance. Underweight alone is not identified as a typical cause of excess estrogen.

Hypogonadism—This condition, where the body produces little or no sex hormones, can lead to low estrogen levels in men. Underweight—Being significantly underweight can impact estrogen production, leading to lower levels of the hormone. This clinical overview explicitly lists underweight as a risk factor for *low* estrogen, not high estrogen, in men and women.

High levels of estrogen in males can be associated with conditions such as **diabetes, tumors of the adrenal glands or testicles, hyperthyroidism, cirrhosis**, aromatase excess syndrome and alcohol use disorder.[5] Lifestyle and metabolic factors like reaching a moderate weight and reducing alcohol intake may affect hormone levels, but obesity is emphasized more than leanness as a contributor to higher estrogen.[5]

Aim for a healthy body weight: Underweight is a risk factor for low hormone levels. Talk with your healthcare provider about dietary changes you may need to ensure you’re getting proper nutrition. The article explains that being underweight is associated with low hormone levels, including estrogen, and recommends reaching a healthy weight to normalize hormones.

Common causes of **high estrogen levels** listed include excess body fat, liver dysfunction, hormone therapy, birth control pills, exposure to xenoestrogens, certain tumors, thyroid issues, alcohol consumption and chronic stress.[10] The article discusses maintaining a moderate body weight for hormone balance and notes that **excess body fat can increase estrogen**, while it does not describe underweight status as a cause of high estrogen.[10]

In a study on estradiol and obesity in men, differences in estradiol levels between normal weight, overweight and obese men were **not significant**, although there was a relative increase of about 10% in estradiol in obese men compared with normal weight men.[11] In the overweight group there was even a decrease compared to normal weight men, and the authors conclude that estrogen production in overweight and obese men with BMI up to 39 kg/m² does not significantly influence endocrine testicular function.[11]

Subsequently, lower LH pulsatility, as well as reduced levels of oestradiol and testosterone, can be observed in females. Estradiol, FSH, and LH are found to be normal in constitutionally thin individuals, whilst being significantly blunted in anorexia nervosa. Although this review focuses mainly on females, it describes underweight and anorexia nervosa as states characterized by reduced estradiol and overall gonadal hormone suppression, consistent with the concept that severe undernutrition tends to lower, not raise, sex steroid levels.

In men, low BMI may lead to hormonal imbalances, including low testosterone, which affects the libido and sperm quality. If a person has a low BMI and low body fat, hormonal regulation becomes a problem, which leads to ovulation problems in women and low testosterone in men. Being underweight affects: Estrogen deficiency: Adipose tissue produces estrogen… Too little of it due to low body fat can affect ovulation or cause amenorrhea. This fertility-focused article notes that low BMI and low body fat are linked to estrogen deficiency in women and low testosterone in men, not to excess estrogen.

Men make estrogen in their testes, brain, skin, and bones. To produce estrogen, these organs chemically convert testosterone into estrogens using an enzyme called aromatase. Because a supply of testosterone is necessary for this conversion, low levels of testosterone can lead to even lower levels of estradiol and other estrogens. This practitioner article explains that male estrogen synthesis depends on aromatization of testosterone; when testosterone is low (as in hypogonadism or undernutrition), estradiol levels typically decrease rather than become excessive.

A Reddit user discussing low estradiol in men suggests that with a last testosterone measurement of 660 ng/dL and very low body fat, "my low body fat might be preventing my body from converting testosterone into estrogen."[14] This reflects the lay perception that **low body fat limits aromatization**, thus tending toward lower estrogen, though it is anecdotal and not a clinical study.[14]

Background knowledge: In endocrine physiology, peripheral conversion of testosterone to estradiol in men occurs largely in adipose tissue via aromatase, so **lower fat mass (as in underweight or very lean men) generally reduces aromatase-mediated estrogen production**. Clinical literature and major health sites consistently list obesity, tumors, liver disease, and certain endocrine disorders as causes of high estrogen in men, whereas **underweight is usually associated with reduced sex hormone levels, including estrogen**. No mainstream endocrine guideline or major review identifies being underweight in males as a typical cause of excess estrogen.