The average person swallows about half-a-ton of food a year — not counting drink — and though the body is remarkably efficient at extracting ( 摄取 ) just what it needs form this huge mixture, it can only cope up to a point. If you go on eating too much of some things and not enough of others, you’ll eventually get out of condition and your health will suffer. So think before you start eating. It may look good. It may taste good. Fine! But how much good is it really doing you? What you eat and the way it affects your body depend very much on the kinds of person you are. For one thing, the genes you inherit form your parents can determine how your body metabolism ( 新陈代谢 ) copes with particular foods. The tendency to put on weight rather easily, for example, often runs in families—which means that they have to take particular care. And your parents may shape your future in another way. The way you are brought up shapes some basic attitudes to food — like whether you have a sweet tooth, nibble (吃零食) between meals, take big mountains or eat chips with everything. Eating habits, good or bad, tend to get passed on. And then there is your lifestyle. How much you spend on food ( time as well as money ), how much exercise you get—these can alter the balance between food and fitness. And finally, both your age and your sex may affect this balance. For example, you’re more likely to put on weight as get older, especially if you’re a woman.