Experts have found a link between childhood obesity and early onset puberty, with resulting adverse effects on the body's ability to reproduce.

Their view, reported in the journal Frontiers in Enocrinology, states that general puberty is starting earlier in girls and the problem is accelerating.

However they also admit that there is still much to learn about the effects of obesity and puberty, as well as its effects on the liver, pancreas and other endocrine glands.

Professor Patrick Chappell, of Oregon State University, said: "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.

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

One theory is that diet is playing havoc with the body clock, causing changes in the balance of hormones.

Disrupted sleep-wake cycles can affect the secretion of hormones such as cortisol, testosterone, and insulin, researchers have found.

Prof Chappell said: "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.

"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."

Previous studies in humans have found correlations 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 behaviour, smoking and early sexual experiences in both girls and boys.

Posted by Penny Hosie