2. Climate control
We humans, like all warm-blooded animals, can keep our core body temperatures pretty much constant regardless of what’s going on in the world around us. We do this by altering our metabolic(新陈代新的) rate, shivering or sweating. Keeping warm and staying cool take energy unless we are in the “thermo-neutral zone”, which is increasingly where we choose to live and work.
There is no denying that ambient temperatures(环境温度) have changed in the past few decades. Between 1970 and 2000, the average British home warmed from a chilly 13C to 18C. In the US, the changes have been at the other end of the thermometer as the proportion of homes with air conditionings rose from 23% to 47% between 1978 and 1997. In the southern states – where obesity rates tend to be highest – the number of houses with air conditioning has shot up to 71% from 37% in 1978.
Could air conditioning in summer and heating in winter really make a difference to our weight?
Sadly，there is some evidence that it does-at least with regard to heating. Studies show that in comfortable temperatures we use less energy.
3.Less smoking
Bad news: smokers really do tend to be thinner than the rest of us,and quitting really does pack on the pounds, though no one isn sure why. It probably has something to do with the fact that nicotine is an appetite suppressant and appears to up your metabolic rate.
Katherine Flegal and colleaGREs at the US National Center for Health Statistics in Hyattsville,Maryland, have calculated that people kicking the habit have been respousible for a small but significant portion of the US epidemic of fatness.From data collected aroud 1991 by the US National Health and Nutrition Examination Survey,they worked out that people wh
