Researchers at the University of Minnesota say decaffeinated coffee in particular appears to offer protection against adult-onset diabetes, but how it does so is unclear.
They suggest that it is possible that the minerals and non-nutritive plant chemicals found in abundance in the coffee bean may have a beneficial effect on blood-sugar levels or protect the pancreas from stress.
The finding was based on a ten year study of more than 28,000 women in Iowa, USA, after they had gone through the menopause.
When the study began, more than 14,000 of them drank one to three cups of coffee per day, 2,875 drank more than six cups, 5,554 four to five cups, 3,231 less than one cup and 2,928 none.
Over the 11 years of the study 1,418 of the women reported on surveys that they had been newly diagnosed with type 2 diabetes.
The research showed that women who drank six or more cups of coffee a day experienced a 33 per cent less risk of developing type 2 diabetes than other women and decaffeinated coffee seemed to be especially effective.
An earlier study in Finland, which has the highest coffee consumption in the world, has also found that men and women who drank 10 or more cups of coffee per day had the lowest risk of adult onset diabetes.
Researcher Dr. Mark Pereira says that having a healthy diet, controlling your weight, and exercising are essential to preventing the onset of diabetes, but drinking coffee has the potential to further reduce risk.
He says the idea that coffee does more harm than good may have to be revised.
The study is published in the Archives of Internal Medicine.
Allison and colleagues have come up with a list of 10 potential obesity risk factors which include increased rates of older mothers, whose children may be more prone to excess weight gain; a range of medications, such as antidepressants, which can promote weight gain; and a decrease in smoking rates, because people often gain weight when they quit and the absence of nicotine, an appetite suppressant encourages snacking.
Genetic factors, such as the heritability of a person's body mass index (BMI), could also be a factor as studies show that BMI has a heritability of about 65 percent.
According to Allison he is not suggesting people should stop taking their prescriptions, keep smoking or turn off the air con, and he says diet and exercise remain key factors in obesity.
Allison believes researchers and policymakers should be "open-minded" about the potential contributors to the obesity problem and not assume that the answer lies in simple solutions such as banning fizzy drinks from schools or installing sidewalks to encourage walking.
Some experts question the claims and say as people stay thin in all different climates, it is unlikely air conditioning plays much of a role and they are also concerned about linking obesity to genetics.
The review is published in the International Journal of Obesity.