Science Briefing: Food is feast for your eyes

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Food is a feast for your eyes

Does that slice of chocolate cake look delicious or is it all in your head?

A report in the current issue of the journal Cell Metabolism highlights evidence of a gut hormone that causes people to eat more by making food appear more tasty.

In a brain-imaging study, researchers from the Montreal Neurological Institute at McGill University found that reward centres respond more powerfully to pictures of food in people who had been given an infusion of the hormone known as ghrelin. The findings suggest that the two drives for feeding – metabolic signals and pleasure signals – are intertwined.

“When you go to the supermarket hungry, all food looks better,” said Alain Dagher, who led the study. “Your brain assigns a cost versus benefit to every food item. We’ve found that it is ghrelin that acts on the brain to make food more appealing.”

This feeding behaviour may have once provided an adaptive advantage to humans. In our plentiful environment, however, it is a likely cause of obesity and its associated diseases.

Ghrelin levels are known to increase before a meal and decrease afterwards, suggesting that it causes hunger and encourages eating. Treatments that disrupt the effects of ghrelin might help combat obesity.

Temperature rise threatens tropics

Global warming is likely to diminish the health of most tropical species, reports a study in the Proceedings of the National Academy of Sciences. In high latitudes, however, the scientists from UCLA and the University of Washington found that limited climate change may move some organisms – especially insects – closer to their optimal temperature.

The biodiversity of the planet is concentrated in tropical climates, where there is a wide variety of species. Many tropical organisms – from insects to amphibians and reptiles – are already living at their optimal physiological temperatures. An increase in temperature could have a negative impact on their population growth rates.

Yet in the short term, global warming will also have opposite effects: While in the tropics, warming will decrease insects’ ability to reproduce, in high latitudes the capacity of organisms to reproduce will rise slightly. But if warming continues, these insects would eventually be adversely affected as well.

“What hurts the insects hurts the ecosystem,” said Curtis Deutsch from UCLA, co-author of the study. “Insects carry out essential functions for humans and ecosystems – such as pollinating our crops and breaking down organic matter back into its nutrients so other organisms can use them.”

http://www.pnas.org/

Women who quit see fast results

Women who stop smoking radically reduce the risk of death from coronary heart disease within five years and have about a 20 per cent lower risk of death from smoking-related cancers, according to a report in this week’s Journal of the American Medical Association.

The report, by researchers at the Harvard School of Public Health, analysed data from the nurses’ health study, asurvey of more than 100,000 women from 1980 to 2004.

In 2000, about 5m premature deaths were attributed to smoking worldwide. The World Health Organisation projects that by 2030 tobacco-attributable deaths will account for 3m deaths in industrialised countries and 7m in developing countries annually.

The researchers found a 13 per cent decrease in the risk of premature death within the first five years of quitting smoking. The risk fell to the level of someone who never smoked 20 years after quitting. For lung cancer mortality, a 21 per cent risk reduction was seen within the first five years.

http://jama.ama-assn.org/

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