【英语时差8，16】人到中年

 Let's say you're an eighteen-year-old male who runs every other day, logging 12 miles a week.   Now fast-forward to your late 40s. Your eating habits are the same. To maintain your high school weight, how many miles a week would you need to run? Believe it or not, you'd have to multiply your weekly mileage¹ 4 and 1/2 times--increasing it from 12 to 54 miles a week!

So unless you take up weekly double marathons in middle-age, it's impossible simply to "outrun" middle-age spread. That's because metabolism² decreases with age--at 50 you just don't burn as many calories as you did at 18. Luckily, there are other factors in this equation. Gradually eating less is one way to make up the difference, since metabolism slows by about 100 calories every ten years. That's equivalent to a tablespoon of butter. To keep pace with metabolic³ changes, your daily menu at 40 could include everything you ate at 30--minus that tablespoon of butter!

But cutting more calories every ten years gets trickier--and limiting food intake⁴ alone isn't the healthiest approach, anyway. Between our 20th and 70th birthdays, most of us lose about 30% of our muscle cells. Loss of muscle mass is the main reason metabolism slows down in the first place, since resting metabolic rate is directly related to lean body mass--that's mostly muscle. Maintaining or increasing muscle mass through strength training ups your metabolism and burns more calories--even while you're sitting on the couch! Two or three sessions a week, using free weights or equipment at a gym, will do the trick.  

1 mileage   

n.里程，英里数；好处，利润

参考例句：

• He doesn't think there's any mileage in that type of advertising.他认为做那种广告毫无效益。
• What mileage has your car done?你的汽车跑了多少英里？

2 metabolism   

n.新陈代谢

参考例句：

• After years of dieting,Carol's metabolism was completely out of whack.经过数年的节食，卡罗尔的新陈代谢完全紊乱了。
• All living matter undergoes a process of metabolism.生物都有新陈代谢。

3 metabolic   

adj.新陈代谢的

参考例句：

• Impressive metabolic alternations have been undergone during embryogenesis.在胚胎发生期间经历了深刻的代谢变化。
• A number of intoxicants are associated with metabolic acidosis.许多毒性物质可引起代谢性酸中毒。

4 intake   

n.吸入，纳入；进气口，入口

参考例句：

• Reduce your salt intake.减少盐的摄入量。
• There was a horrified intake of breath from every child.所有的孩子都害怕地倒抽了一口凉气。