Hello Nature readers,
Today we learn one possible reason that there is a link between obesity and some cancers. Plus, we see a building sacrifice part of itself so that the rest can survive and discover the five best science books to read this week.

The fat-gut-cancer link

A study in mice and people suggests why there is a link between obesity and some cancers: a high-fat diet increases the number of Desulfovibrio bacteria in the gut. These release leucine, an amino acid, which encourages the proliferation of a kind of cell that suppresses the immune system. With a suppressed immune system, breast cancer tumour growth increases. "It's a provocative finding that will open up new avenues that we should be thinking about," says nutritional biologist Stephen Hursting.

Data lacking in US bird flu outbreak

H5N1 avian influenza has climbed "the first step of the pandemic stairs," in the words of virologist Thomas Peacock: it has improved at making copies of its genome in mammals. The virus has been circulating in US cattle since perhaps November. Scientists are eager to monitor the pathogen's evolution and assess its pandemic risk, but the US Department of Agriculture has not released data on infections in a timely manner, they contend. A spokesperson for the USDA says that national laboratories have conducted more than 7,500 tests since the start of the outbreak.

Found: a long-lost branch of the Nile

The remains of an ancient branch of the Nile River has been found near the Giza pyramid complex in Egypt — hinting at why so many were built there. The pyramids there are now many kilometres away from the Nile. Satellite images and geological data now confirm that a tributary of the river — which researchers have named the Ahramat Branch — used to run nearby several thousand years ago. The waterway would have provided a convenient way to transport materials to the sites.

Public health needs to note sex and gender

From the expression of certain heart-tissue genes to the response to cancer treatment, we have only scratched the surface of how human health is affected by the variables of sex and gender, write three scientists. The impact is clear: between 1997 and 2000, for example, eight drugs were pulled from the US market because it turned out they put women at greater risk of side-effects than men; the error cost pharmaceutical companies and taxpayers an estimated US$1.6 billion per drug. Clinical trials, cell lines and mouse studies all need to be more diverse as a matter of routine, argue cancer researcher Sue Haupt, neurologist Cheryl Carcel and global-health researcher Robyn Norton. "Likewise, the culture of medicine must be transformed so that approaches to treatment evolve in response to the data."

Futures: Explaining scientific concepts…

An effort to make a high-tech system comprehensible goes off the rails in the latest short story for Nature's Futures series.

Five best science books this week

Andrew Robinson's pick of the top five science books to read this week includes a call for us to embrace recycled water (in other words, drinking cleaned sewage). Plus, a gloriously illustrated look at John James Audubon's watercolour birds and an optimistic look at our future with robots.

Video: 'tactical sacrifice' can save a building

Inspired by lizards who shed their tails to escape predators, researchers have designed a building that sacrifices part of itself so that the rest can survive. The connections between columns are just strong enough so that they spread the load when under normal stress, but break when it becomes unbearable. The results: a building that can completely collapse in sections without pulling down the entire structure.