Men who were obese as children tend to have shorter penises

A study in Vietnam investigating men who came to Hanoi Medical University Hospital for reproductive health checks found that those who were obese as children tended to have shorter penises as adults. Penis size was not associated with participants’ current body mass index, but there were some weak associations with waist and hip circumference. The paper was published in the Journal of Sexual Medicine.

The size and appearance of the human penis has long been a topic of interest both in medical research and in everyday discussions. For many men, penis size is associated with self-esteem and feelings of masculinity. Media, and particularly social media, often discuss the significance of penis size, promoting the idea that there is an “ideal size” and making penis size a source of anxiety for some men. However, although there are rare medical conditions (such as micropenis) that involve extreme deviations from the average penis size, most men who worry about the size of their penis fall within the normal range.

In scientific research, penis size is typically assessed using several measurements, including length and diameter (or circumference), in flaccid, stretched, and erect states. For instance, length is often measured along the top of the penis from the pubic bone to the tip of the glans, while girth is measured around the mid-shaft. Studies show that average erect penis length is about 13 to 14 centimeters (5 to 5.5 inches), with natural variation among individuals and populations.

Study author Bac Hoai Nguyen and his colleagues note that penile development is a complex process influenced by genetics, hormones, and environmental factors. One such potential factor is obesity, particularly in childhood. Obesity is associated with declines in the male sex hormone testosterone during puberty, and testosterone is important for penile development. With this in mind, they conducted a study aiming to examine the association between prepubertal obesity and penis size in Vietnamese men.

Study participants were 290 heterosexual men who visited the Department of Andrology and Sexual Medicine of Hanoi Medical University Hospital for reproductive health check-ups between June 2023 and July 2024.

Study authors measured participants’ height, waist and hip circumference, length of the second and fourth digits on both hands, and penis dimensions: pubic-to-tip flaccid length, skin-to-tip flaccid length, and pubic-to-tip stretched length. Study authors also measured the diameter of the glans and the mid-shaft in the flaccid state. They also had participants estimate their body mass index when they were 10 years old by adjusting the characteristics of 3-dimensional models. The age of 10 was selected because that is a time just before the start of puberty for most children.

Results showed that 63% of participants had a normal body mass index when they were 10 years old. Of these, 26% became overweight, 31% became obese, and 4% became underweight as adults. Of the participants who were overweight as children, 30% had a normal body mass index as adults, while 46% became obese. Of the individuals who were obese as children, 27% became normal-weight, 24% became overweight, and none became underweight.

On average, participants’ penises had a pubic-to-tip flaccid length of 8.9 cm, which increased to 14.4 cm when stretched. The average diameter of the penis was 2.93 cm at the glans and 2.83 cm at the middle. The study found that obese men had slightly wider mid-shaft diameters than overweight men, but not necessarily compared to normal-weight men.

Participants who were obese as children tended to have shorter penises as adults. This was the case for stretched penis length and both measures of flaccid length. Higher waist circumference as an adult was associated with shorter skin-to-tip flaccid penis length. Higher hip circumference was associated with slightly longer pubic-to-tip stretched length. Penis dimensions were not associated with participants’ body mass index in adulthood.

“Childhood obesity is associated with penile growth, while adulthood obesity relates to the appearance of the penis rather than the actual size. Thus, there is a need for early interventions to mitigate the potentially long-term effects of childhood obesity on penile development,” the study authors concluded.

The study sheds light on the links between obesity and penile development. However, it should be noted that the study was conducted on a group of men seeking medical help for reproductive issues and may not be representative of the general population.

The paper, “Associations between obesity across the lifespan and adult penis dimensions: a retrospective observational study of Vietnamese men using 3D-modeled prepubertal BMI,” was authored by Bac Hoai Nguyen, Quan Minh Pham, Anh Bui Quoc Nguyen, Anh Phuong Nguyen, Vu Bui Duy Nguyen, Andrea Sansone, and Emmanuele A. Jannini.