What biological aspect increases as humans age?

As humans age, body fat levels tend to increase due to several biological and physiological changes. One of the main reasons for this increase is the shift in body composition that typically occurs with aging. As individuals get older, there is often a decrease in muscle mass, particularly if regular physical activity is not maintained. This loss of muscle, known as sarcopenia, can lead to a reduced metabolic rate, meaning that the body burns fewer calories. Consequently, if calorie intake does not decrease accordingly, this imbalance can result in an increase in body fat levels.

Additionally, hormonal changes such as decreased levels of growth hormone and sex hormones (like estrogen and testosterone) contribute to the redistribution and accumulation of fat tissue. Aging is also associated with a reduction in physical activity for many individuals, which further exacerbates the increase in body fat.

Other choices do not reflect the general trend associated with aging. For instance, metabolic rate typically decreases with age rather than increases. Muscle repair efficiency often diminishes, making recovery from exercise and injury more prolonged and less effective. Although calcium absorption can change with age, it usually decreases rather than increases, leading to a higher concern for osteoporosis in older adults. Hence, the increase in body fat levels is a common biological aspect observed in