BALLOONING: Half of all Bendon bras sold in New Zealand are now a D cup or larger.

My face is up here, buddy.

New Zealand women's breasts have been getting bigger over the last decade, with the most popular cup size moving up two notches.

The news might not come as a surprise to some men, who have been copping a bigger eyeful in recent years.

Bendon spokeswoman Rachael Parkin said the average bust size had been steadily increasing in the last decade, particularly with younger women.

"D cups and larger now account for nearly half of all the Bendon bras sold in New Zealand," she said.

Bendon's Newmarket store in Auckland had seen their most popular size go from a 10C up to 12D/DD size in the last two years.

"We are also seeing young girls are coming into our stores with larger busts much more often now."

For Triumph, the average bra size moved from a 12B in 2001 to between a 14C and 14D.

National sales manager Anita Clelland said the demand for larger bra sizes was probably recognised 10 to 15 years ago, particularly in the younger market.

Massey University Associate Professor in Human Nutrition Jane Coad said there was no significant research behind the phenomenon, but suspected it could be caused by many factors.

"One is that everyone is getting bigger," she said. "Women get bigger breasts because fat is deposited in the breasts, sides and bottom."

People have been growing in size, with the World Health Organisation describing obesity as an epidemic.

Obesity rates in New Zealand have been on the rise, going from 9 per cent of men and 11 per cent of women in 1977 to 20 and 22 per cent respectively in 2003.

The most recent Health Ministry figures showed one in three adults was overweight, and one in four was obese.

Coad said there were also estrogen compounds in the environment from packaging, chemicals and preservatives in foods.

The female hormone controls female physiology, affecting breast growth and metabolism.

Coad said American studies had found estrogen in contaminated water had feminised fish, but there was no direct evidence between hormone in water and breast size.

"We know that there are definitely estrogen compounds in the water that are biologically active.

"What we don't know is how much gets into the human food supply and, if it does, what effects it has."

She said another explanation for bigger breasts could be a better-nourished generation hitting early puberty.

"They have a higher plane of nutrition in childhood, and girls respond to this by having early puberty."

Coad said there wasn't enough research on the subject, as big breasts had no severe health risk.

"People for whom body shape is important or who put a lot of stress on their back by being on their feet all the time might have to change careers.

"But it's not having a big enough impact to justify funding research," she said.