5. A little older…

　　Some groups of people just happen to be fatter than others. Surveys carried out by the US National Center for Health Statistics found that adults aged 40 to 79 were around three times as likely to be obese as younger people. Non-white females also tend to fall at the fatter end of the spectrum: Mexican-American women are 30% more likely than white women to be obsess, and black women have twice the risk.

　　In the US, these groups account for an increasing percentage of the population. Between 1970 and 2000 the US population aged 35 to 44 grew by 43%.the proportion of Hispanic-Americans also grew, from under 5% to 12.5% of the population, while the proportion of black Americans increased from 11% to 12.3%.these changes may account in part for the increased prevalence of obesity.

　　6. Mature mums

　　Mothers around the world are getting older. In the UK, the mean age for having a first child is 27.3, compared with 23.7 in 1970. Mean age at first birth in the US has also increased, rising from 21.4 in 1970 to 24.9 in 2000.

　　This would be neither here nor there if it weren’t for the observation that having an older mother seems to be an independent risk factor for obesity. Results from the US National Heart, Lung and Blood Institute’s study found that the odds of a child being obese increase 14% for every five extra years of their mother’s age , though why this should be so is not entirely clear.

　　Michael Symonds at the University of Nottingham, UK, found that first-born children have more fat than younger ones. As family size decreases, firstborns account for a greater share of the population. In 1964, British women gave birth to an average of 2.95 children; by 2005 that figure had fallen to 1.79. In the US in 1976, 9.6% of woman in their 40s had only one child; in 2004 it was 17.4%. This combination of older mothers and more single children could be contributing to the obesity epidemic.

　7. Like marrying like

　　Just as people pair off according to looks, so they do for size. Lean people are more likely to marry lean an d fat more likely to marry fat. On its own, like marrying like cannot account for any increase in obesity. But combined with others —— particularly the fact that obesity is partly genetic, and that heavier people have more children-it amplifies the increase form other causes.

　　1. What is the passage mainly about?

　　A) Effects of obesity on people’s health

　　B) The link between lifestyle and obesity

　　C) New explanations for the obesity epidemic

　　D) Possible ways to combat the obesity epidemic

　　2. In the US Nurses’ Health Study, women who

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