Childhood obesity may cause fertility problems

[Posted: Wed 01/08/2012 by Gillian Tsoi www.irishhealth.com]

Childhood obesity may result in the early onset of puberty and lead to a reduced ability to reproduce, according to scientists in the US.

They believe that the dramatic increase in childhood obesity in recent decades may have impacts that go beyond the usual health concerns - especially in females.

Obesity could be related to growing problems with infertility and various other physical and psycho-social concerns, say the experts from Oregon State University.

For thousands of years of evolution, poor nutrition or starvation were a greater concern than the overabundance of food that is present in the modern world. Human bodies may now be scrambling to adjust to a problem that is fairly new.

"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," said Patrick Chappell, professor at Oregan State University and an author of the recent report.

"Either extreme of the spectrum, anorexia or obesity, can be associated with reproduction problems," he said.

In general, puberty appears to be starting earlier in girls: it is being accelerated.

One possible affect on the timing of puberty 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."

Molecular mechanisms have only started to be uncovered in the past decade, the researchers said, and the triggers that control pubertal development are still widely debated. For millennia, many mammals made adjustments to reduce fertility during periods of famine. But it now appears that an excess of fat can also be contributing to infertility rates and reproductive diseases.

Some studies in humans have found links between early puberty and the risk of reproductive cancers, adult-onset diabetes and metabolic syndrome.

Early onset puberty has also been associated with increased rates of depression and anxiety in girls, studies have found, as well as increased delinquent behavior, smoking and early sexual experiences in both girls and boys.

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. While humans show natural variations in pubertal progression, the signals that control this timing are unclear.

According to the US experts, additional research is needed to better understand the effect of these processes on metabolism, hormones and other development processes.

The report was published in Frontiers in Endocrinology.