Young men with late puberty have healthier fat-to-muscle ratios

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Mar 20 2025

Young men who hit puberty later have lower bone mass but healthier fat-to-muscle ratios, suggesting that delayed maturation may offer long-term body composition benefits.

Study: Association between pubertal timing and bone and body composition in young adult men. Image Credit: Lapina / Shutterstock

In a recent study published in the journal Scientific Reports, researchers examined how the timing of puberty affects body composition and bone density in young men.

They found that those who experienced puberty earlier had higher bone density but largely similar body composition, apart from a slightly higher BMI and trunk fat mass, while those who experienced puberty later had lower bone mass, fat mass, and lean mass.

The study highlights that pubertal timing influences body and bone composition even after reaching adult height.

Background

Puberty is a crucial period of physical development influenced by genetics, hormones, body weight, and nutrition. The timing of puberty varies widely and can affect long-term health.

Later puberty increases the risk of osteoporosis in women, and studies suggest similar risks for men. Late puberty is associated with decreased bone mineral density (BMD) and higher fracture risk. However, some research indicates that men with later puberty may, over time, reach a similar BMD to those with early puberty.

Researchers often use peak height velocity to estimate puberty timing in boys, but voice break is a widely used and distinct marker. Studies show that the timing of voice break is genetically linked to early puberty markers like testicular growth.

Data from the Copenhagen Puberty Study suggest that voice break generally occurs around 13.6 years and correlates with rising testosterone levels and testicular enlargement. Even after reaching adult height, skeletal development continues until the achievement of peak bone mass (PBM), particularly in longer bones.

PBM is a key factor in osteoporosis risk later in life, and muscle growth during puberty plays a critical role in bone strength. While puberty timing influences biological age and maturation, it is unclear how these differences persist into young adulthood. Further research is needed to understand the long-term effects of pubertal timing on bone and muscle development.

About the study

This study explored the relationship between puberty timing and body and bone composition in young men. Researchers used dual-energy X-ray absorptiometry (DXA) to assess bone density, muscle mass, and fat distribution.

Participants, who were young Danish males undergoing mandatory military fitness exams, completed questionnaires about their pubertal milestones, including self-reported voice break timing. They were categorized as experiencing puberty earlier, at the same time, or later than their peers.

From 2012 to 2019, 2,311 men participated in the study. The study included reproductive health assessments, physical exams, and blood tests. BMD, bone mineral content (BMC), and body composition were measured. DXA scans were calibrated regularly to ensure accuracy, and bone mineral apparent density (BMAD) was used to adjust for differences in bone size.

Statistical analyses compared groups based on pubertal timing. Linear regression models, adjusted for factors like age, body mass index (BMI), physical activity, smoking, and alcohol intake, examined associations between voice break timing and DXA measurements.

Additional analyses tested the validity of findings by considering other pubertal markers, such as the development of pubic hair and testis size.

Findings

The study found that the timing of puberty, based on self-reported voice break, was linked to bone and body composition in young men. Among the 2,056 participants analyzed, 20% reported experiencing an earlier voice break, while 17% had a later one.

Men with earlier voice breaks had higher BMC, BMD, and BMAD at the lumbar spine and femoral neck. Even after adjusting for factors like age, BMI, smoking, and physical activity, they maintained higher lumbar BMD and total body BMD. Lumbar BMAD was also significantly higher, indicating denser bone relative to size. In contrast, those with later voice breaks had lower bone volume, bone area, and lumbar BMC but no significant differences in lumbar areal BMD or BMAD.

In terms of body composition, men with earlier voice breaks had a higher BMI and were more likely to be overweight. Those with later voice breaks had lower BMI, body weight, muscle mass, lean mass, and total fat mass. However, they had a higher percentage of lean mass and a lower fat-to-muscle ratio, suggesting a healthier body composition despite lower absolute mass.

Similar trends were observed when puberty timing was assessed through other milestones, such as pubic hair and testis growth. These findings suggest that puberty timing influences bone and body composition, with earlier puberty linked to higher bone density and greater absolute body mass.

Conclusions

This research provides insight into how variations in puberty timing may have lasting effects on body and bone composition, even after adult height is reached.

Men who experienced a later voice break had lower bone volume and mineral content in the lumbar spine but showed no differences in total body or femoral bone density. They also had lower muscle mass, lean mass, BMI, and fat mass, resulting in healthier body compositions with lower fat percentages and better fat-to-muscle ratios. In contrast, men whose voices broke earlier had higher bone mineral density but no major differences in body composition, except for slightly higher BMI and trunk fat mass.

The authors suggest that men with later puberty may not have fully reached adult body weight, muscle mass, or bone volume by age 19 despite attaining adult height—indicating that physical maturation continues beyond linear growth. Thus, pubertal timing influences bone and body composition into young adulthood, with later puberty associated with ongoing bone maturation and delayed attainment of peak physical mass.