Library.

“Obesity in men lowers testosterone levels and thereby reduces criminal perpetration rates.”

The proposed reduction in criminal perpetration is unsupported. Obesity can lower testosterone in men, but no evidence demonstrates that this hormonal effect causes less offending. The only cited longitudinal study examining obesity and later criminal outcomes instead reported higher adult felony-conviction prevalence among people with pediatric obesity, although it did not isolate men or test testosterone as a mediator.

“Obesity makes men less violent because it lowers testosterone levels.”

The proposed causal explanation is unsupported. Obesity is associated with lower testosterone in men, but research does not show that this makes men less violent; testosterone’s relationship with human aggression is weak and does not establish causation. Several behavioral studies instead associate higher body mass with greater aggression or externalizing behavior, while limited arrest data cannot prove the claimed mechanism.

“In males living in the Kalahari environment, elevated circulating testosterone indicates that a sexual-selection-related physiological axis remains active in the population despite thermal stressors.”

The claim is not supported by the cited evidence. The only directly relevant study of desert-dwelling human males does not show elevated testosterone, and the broader heat-stress literature mostly points in the opposite direction: thermal stress tends to suppress testosterone and impair reproductive physiology. The inference to an active sexual-selection-related axis in Kalahari males is therefore unproven.

“Low testosterone levels can cause obesity in men.”

Low testosterone can contribute to fat gain and, in some men, to obesity. Mechanistic, longitudinal, and clinical evidence indicates that testosterone deficiency promotes adiposity and visceral fat accumulation, especially in more severe hypogonadal states. However, the relationship is bidirectional, and obesity is more often a cause of low testosterone than the primary result of it.

“Low testosterone levels can be a cause of underweight in people of any sex.”

The evidence does not support low testosterone as a cause of underweight. Across the cited medical literature, low testosterone is associated mainly with increased adiposity, reduced lean mass, and weight gain or impaired weight loss, not low body weight. The claim also confuses loss of muscle with being underweight and overgeneralizes across sexes without support.

“In men, having too little body fat causes androgen levels to decrease.”

The evidence does not support the general claim that low body fat in men lowers androgens. High-quality studies more consistently show the opposite pattern: higher body fat is associated with lower testosterone, and reducing excess fat often improves it. A possible exception may exist in extreme leanness with severe energy deficit, but that is narrower and less well supported than the claim states.

“Testosterone is the principal endocrine mechanism by which sexual selection translates into morphological sexual dimorphism.”

The evidence shows testosterone is an important and often central hormonal mediator of sexually selected, male-typical morphology in many vertebrates. But the claim goes too far by presenting it as the principal endocrine mechanism in general. Credible sources show multiple alternative hormonal pathways and taxon-specific exceptions, so the broad formulation is only partly supported.

“Under thermal stress, elevated cortisol can reduce testosterone levels, affecting sexually dimorphic traits.”

The evidence supports the claim in broad terms. Heat or thermal stress can be associated with higher cortisol and lower testosterone, and glucocorticoids are well documented to suppress testosterone production. The main caveat is that heat can also lower testosterone through other pathways, so cortisol is a plausible mechanism, not always the sole or primary one; effects on sexually dimorphic traits are better supported for sustained hormone changes than for short-term stress.

“Reducing dietary intake of added sugar increases testosterone levels in men.”

Evidence suggests sugar can be linked to lower testosterone, but it does not show that simply reducing added sugar reliably raises testosterone in men. The strongest studies show short-term testosterone dips after glucose and observational links with sugary drinks, while long-term diet studies usually mix sugar reduction with weight loss and other metabolic changes. The causal claim is stronger than the evidence supports.

“Sugar deficiency increases testosterone levels in men.”

The evidence does not support the idea that “sugar deficiency” raises testosterone in men. Studies more narrowly suggest that excess sugar or glucose loads can lower testosterone, and that cutting excessive sugar may improve levels in some metabolically unhealthy men. That is not the same as showing that a deficiency of sugar increases testosterone, especially across men in general.

“In men, testosterone secretion is highest in the morning, making male aggression highest in the morning.”

Morning testosterone peaks in many men are well documented, but the claim’s main takeaway does not follow. Evidence does not show that male aggression is highest in the morning, and baseline testosterone has only a weak, context-dependent relationship with aggression. Age and health status also affect how strong the morning hormone peak is.

“Practicing combat sports has a stronger effect on maintaining or increasing testosterone levels compared to most other sports.”

The best available evidence directly contradicts this claim. A meta-analysis published in a high-authority NIH-indexed journal found no statistically significant difference in testosterone response between combat sports and other sports. Multiple studies show testosterone can actually decrease after combat sports activity, and basal testosterone levels in martial artists are statistically indistinguishable from those of other athletes. Resistance training and HIIT produce comparable or robust testosterone responses, undermining any claim of combat sports superiority.

“Low testosterone is the primary cause of low libido in men.”

Low testosterone is a well-documented contributor to reduced libido, but no authoritative clinical source identifies it as the "primary" cause. Major medical references — including the Merck Manual, Mayo Clinic, Cleveland Clinic, and the Endocrine Society — consistently describe male libido as multifactorial, with psychological factors (depression, anxiety, relationship problems), medications, chronic conditions, and lifestyle factors frequently playing equal or greater roles. The claim conflates testosterone's important role with singular primacy, an assertion the clinical evidence does not support.

“Zinc supplementation increases testosterone levels and improves sexual performance in men.”

Zinc supplementation can raise testosterone — but primarily in men who are already zinc-deficient, not men generally. The claim's universal framing omits this critical qualifier, which is consistently emphasized across the strongest peer-reviewed evidence, including a 2022 systematic review of 38 studies. The "sexual performance" sub-claim relies almost entirely on animal studies involving lead-exposed rats, with no robust human clinical trial demonstrating this benefit in typical men. A large multicenter human RCT found no reproductive improvement and even documented harm from zinc supplementation.

“Higher cholesterol levels in the body lead to higher testosterone production.”

While cholesterol is a necessary biochemical precursor for testosterone synthesis inside cells, the claim that "higher cholesterol levels in the body" lead to higher testosterone production is not supported by human evidence. Multiple population-level studies (including NHANES data) find no association—or even an inverse relationship—between circulating cholesterol and testosterone levels. The rate-limiting step is intracellular cholesterol transport into mitochondria, not the amount of cholesterol in the bloodstream. Research also shows that low testosterone can itself raise circulating cholesterol, reversing the claimed causal direction.

“Cold plunges increase testosterone levels in men.”

This claim is not supported by the scientific evidence. The highest-quality peer-reviewed studies show cold-water immersion either blunts or decreases testosterone levels in men. The only sources supporting the claim are commercial cold plunge and cryotherapy vendors with clear financial conflicts of interest, and even one of those admits no definitive clinical trial exists. Any reported increases are trivially small (~5%), transient, and within normal hormonal fluctuation — not meaningful testosterone boosts.