A sharp spike in childhood obesity may more than damage overall health -- it could be disrupting the onset of puberty and erode the ability to reproduce, especially in females, according to a study.

Human bodies may be scrambling to adjust to a problem that is fairly new. For thousands of years of evolution, poor nutrition or starvation were a greater concern, rather than an overabundance of food.

"The issue of so many humans being obese is very recent in evolutionary terms, and since nutritional status is important to reproduction, metabolic syndromes caused by obesity may profoundly affect reproductive capacity," Patrick Chappell, assistant professor of veterinary medicine at Oregon State University and study author, was quoted as saying in the journal Frontiers in Endocrinology.

Researchers are still learning more about the overall impact of obesity on the beginning of puberty and effects on the liver, pancreas and other endocrine glands, Chappell said. In general, puberty appears to be starting earlier in girls. It is being accelerated, according to a university statement.

This may have several effects, scientists have found. One theory is an impact on kisspeptin, a recently characterized neuro-hormone necessary for reproduction. Normal secretions of this hormone may be disrupted by endocrine signals from fat that serve to communicate to the brain.

Another possible affect on pubertal timing, and reproduction in general, is disruption of circadian clocks, which reflect the natural rhythms of night and day. Disrupted sleep-wake cycles can affect the secretion of hormones such as cortisol, testosterone, and insulin, researchers have found.

"Any disruption of circadian clocks throughout the body can cause a number of problems, and major changes in diet and metabolism can affect these cellular clocks," Chappell said.

"Disruption of the clock through diet can even feed into a further disruption of normal metabolism, making the damage worse, as well as affecting sleep and reproduction," he added.