老年人的肌萎缩是可以预防的，甚至是可逆的

新陈代谢的神话The Metabolism Myth

没有生物学上的理由，随着年龄的增长人会变胖

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你听人说过，也许你自己也说过:“大约35岁时，我的新陈代谢减慢了，脂肪开始累积。”明显的推论是新陈代谢的减慢是不可避免的，就像黑夜白天一样。这根本不是事实。男性和女性，平均来说，确实患有渐进式肥胖; 在西方世界，35岁的男性平均每年能获得大约一磅的脂肪，直到生命的第六个十年。女性通常会获得更多的比例。然而，原因并不是新陈代谢的老化。

一个标准

肌肉的能量需求保持不变

《运动生理学》(Exercise Physiology)是Drs.William D. McArdle, Frank I. Katch和Victor L. Katch (Lea & Febiger，第3版)的优秀教材告诉我们，随着年龄的增长，人们会变得越来越胖。大学时代的男性平均15%的身体脂肪和年长的男性通常约25%。女性在年轻时携带的脂肪约为25%，到50岁时，会上升到35%或更多。

然而，医生们赶快补充说，这些“平均”价值不应该被认为是正常的。“我们认为，对于年轻男性和女性来说，‘太胖’的标准应该是: 男性高于20%，女性高于30%。”男人和女人随着年龄的增长，可能没有比这更胖的生理原因了。他们解释说，身体脂肪的增加更多的是一种活动的功能，而不是年龄。不活动会导致肌肉的丢失。而肌肉的丧失，而不是老化的新陈代谢，是导致肥胖的主要原因。老化过程保留下来的肌肉就像以前一样活跃。

以下是劳伦斯·e·兰姆博士提出的事实。在他的书中，由明尼苏达大学的Ancel Keys博士领导的“称重游戏Weighting Game”(Lyle Stuart)研究人员测量了不同年龄、不同体重的人的能量需求。他们发现，在20岁至60岁的男性和女性中，无脂体重(身体重量减去身体脂肪)的能量要求是相当稳定的。所有的受试者，无论他们的性别或年龄，在静止的条件下，每公斤肌肉每小时燃烧1.28的卡路里。

为了真正了解这里发生了什么，我们需要定义“新陈代谢”。新陈代谢是身体里的化学和物理过程，它们制造和破坏组织并释放能量，从而产生热量。当我们努力的时候，我们的新陈代谢会加速，燃烧更多的卡路里。当我们休息的时候，我们的新陈代谢会减慢，我们消耗的卡路里也更少。但即使是休息，也应该强调，我们继续消耗卡路里。

关键是肌肉

肌肉的减少会导致新陈代谢的减慢

这是真的:新陈代谢通常随着年龄的增长而下降。换句话说，老年人平均每磅体重消耗的热量比年轻人少。但那是因为他们的肌肉量更低。

威廉·埃文斯(William Evans)博士和欧文·h·罗森伯格(Irwin H. Rosenberg)在《生物标记》(Biomarkers)一书中证实了这一点，他们的里程碑式的书是关于控制衰老过程的(西蒙与舒斯特出版社，1991年)。如果你的肌肉量减少，就像大多数中年人一样，你对氧气的代谢需求和你的热量需求就会下降。这是因为肌肉组织是需要营养的活跃组织。脂肪是被动的;它只是作为身体能量的储存形式存在。“我们认为，老年人的肌肉量下降几乎是导致其基础代谢率逐渐下降的主要原因。”

恶性循环

新陈代谢减慢导致脂肪增加

埃文斯和罗森伯格解释说，肌肉量的减少——以及它引起的新陈代谢减缓——形成了一个恶性循环。当我们的肌肉量下降时，我们的卡路里就会随之下降。根据生物标志物的作者，大多数人要维持体重在同样的水平，每隔十年每天需要减少摄入大约100卡路里的热量。当然，问题是我们继续吃同样的东西。“太多的卡路里加上运动太少，肌肉减少，代谢率的下降会导致越来越多的脂肪。” 他们的结论是，这种循环只会随着时间的推移而恶化——除非被一个增加肌肉和恢复新陈代谢的程序打破。

饮食，当然，有助于控制缓慢的肥胖。你应该避免高热量的食物，重点是高纤维和高体积的食物。吃大量的水果、蔬菜和全谷类食物。但“老化代谢”的主要解决方案是运动。运动时燃烧卡路里，运动后你继续消耗比休息更多的卡路里。即使是轻微的运动也会让你在一小时后燃烧额外的卡路里。如果你锻炼的时间越来越长，12小时后你的能量需求仍然会提高。甚至在休息的时候，新陈代谢活跃的肌肉仍然使用能量。你的肌肉越多，你消耗的卡路里就越多。这就是为什么举重训练如此重要。它建立和维持燃烧卡路里的肌肉组织，使你保持苗条。举重会使你的新陈代谢的火焰更加强烈。

不要气馁

老年人的肌肉跟年轻人的肌肉的反应一样

不要让任何人告诉你，随着年龄的增长，你的肌肉尺寸和力量都不会增加。埃文斯和罗森博格以及他们在塔夫茨大学美国农业部人类营养研究中心的同事们发现，“老年人的肌肉和年轻人一样，对重量训练的反应也一样。”令人吃惊的是，一项为期8周的力量训练计划，由87岁至96岁的女性参加，她们被限制在疗养院，结果是力量增加了三倍，肌肉尺寸增加了10%。

他们的重要结论是:“随着我们年龄的增长，大部分肌肉的衰减是可以预防的，甚至是可逆的。”

劳伦斯·兰姆博士对此表示赞同:“开发一种老的肌肉就像培养年轻肌肉一样。你可能需要更加小心和循序渐进进步，但是你可以做到。另外，保持训练，偶尔坚持你的极限，你会保持你的肌肉和你的新陈代谢。

归根结底，如果你不慢下来，你的新陈代谢就不会减慢。

The Metabolism Myth

There's no biologic reason to get fatter as you grow older

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You've heard people say it, maybe you've even said it yourself: "At about 35 my metabolism slowed down, and the fat started to accumulate." The clear inference is that a slowing of metabolism is inevitable, like night follows day. That's simply not true. Men and women, on average, do suffer from creeping obesity; in the Western world, the average 35-year-old male gains about a pound of fat each year until the sixth decade of life. Women often gain proportionately more. The reason, however, is not an aging metabolism.

One Criterion

Energy requirement of muscle remains constant

Exercise Physiology, the excellent textbook by Drs. William D. McArdle, Frank I. Katch and Victor L. Katch (Lea & Febiger, 3rd Edition), tells us that people do tend to get fatter with age. College-age men average 15% bodyfat and older men are usually about 25%. Women in their youth carry bodyfat about 25% and move up to 35% or more by age 50. The doctors hasten to add, however, that these "average" values should not be accepted as normal. "We believe that one criterion for what is considered 'too fat' should be that established for younger men and women - above 20% for men and above 30% for women. There is probably no biologic reason for men and women to get fatter as they grow older." Increases in bodyfat, they explain, are more a function of activity than age. Inactivity results in loss of muscle. And loss of muscle, not an aging metabolism, is the primary cause of creeping obesity. The muscle that remains is as metabolically active as ever.

Here are the facts as presented by Lawrence E. Lamb, M.D., in his book The Weighting Game (Lyle Stuart) Researchers led by Dr. Ancel Keys at the University of Minnesota measured the energy requirements of people of different ages with different amounts of bodyfat. They found that the energy requirement of fat-free body weight (weight of the body minus the bodyfat) were remarkably constant for both men and women between the ages of 20 and 60. All the subjects, no matter what their sex or age, burned about 1.28 calories per hour per kilogram (2.2 lbs.) of fat-free body weight, under resting conditions.

To really understand what's going on here, we need to define "metabolism." Metabolism is the chemical and physical processes in the body that build and destroy tissue and release energy, thereby generating heat. Our metabolism speeds up when we exert ourselves, and we burn more calories. Our metabolism slows down when we are at rest, and we burn fewer calories. But even at rest, it should be emphasized, we continue to expend calories.

It's The Muscle

Reduced muscle mass causes slowing metabolism

It's true: metabolism usually falls with age. In other words, older people on average burn fewer calories per pound of bodyweight than do younger people. But that's because their lean body mass is less.

William Evans, Ph.D. and Irwin H. Rosenberg, M.D. confirm this in Biomarkers, their landmark book about controlling the aging process (Simon & Schuster, 1991). If you have a reduced amount of muscle, as most middle-aged people do, your metabolic demand for oxygen and your caloric needs decline. That's because muscle tissue is active tissue requiring nourishment. Fat is passive; it just sits there as a storage form of body energy. "We feel that older people's reduced muscle mass is almost wholely responsible for the gradual reduction in their basal metabolic rate."

Vicious Cycle

Slowing metabolism sets up fat gain

Evans & Rosenberg explain that this reduction in muscle mass - and the slowing of metabolism that it causes - sets up a vicious cycle. As our muscle mass falls, our calorie needs fall with it. According to the authors of Biomarkers, most people need to take in about 100 calories per day less each decade to maintain a level body weight. The problem, of course, is that we continue eating the same. "Too many calories coupled with too little exertion, a reduced musculature, and a declining metabolic rate add up to more and more fat." This cycle, they conclude, will only worsen over time - unless broken by a program that increases muscle and restores lost metabolism.

Diet , of course, helps to control creeping obesity. You should avoid calorie-dense foods and emphasize foods high in fiber and bulk. Eat plenty of fruit, vegetables and whole grains. But the main solution for an "aging metabolism" is exercise. Exercise burn calories while you exercise, and after exercise you continue to use more calories than at rest. Even mild exercise leaves you burning extra calories an hour later. If you exercise harder and longer, after 12 hours your energy requirements will still be elevated. And even at rest, your metabolically active muscles still use energy. The more muscle you have, the more calories you use, round the clock. That's why weight training is so important. It builds and maintains the calorie-burning muscle tissue that makes - and keeps - you lean. Lifting weights keeps your metabolic fires burning strongly.

Don't Be Discouraged

Old muscle just as responsive

And don't let anyone tell you that you can't increase your muscle size and strength as you get older. Evans and Rosenberg and their colleagues at the U.S. Department of Agriculture's Human Nutrition Center on Aging at Tufts University have found that "the muscles of elderly people are just as responsive to weight training as those of younger people." Startlingly, an 8-week program of strength training by 87- to 96-year-old women confined to a nursing home resulted in a tripling of strength and a muscle-size increase of ten percent.

Their important conclusion: "Much of the loss of muscle as we age is preventable - and even reversible."

Dr. Lawrence Lamb agrees: "Developing an old muscle is just like developing a young muscle. You may need to be more careful and progress slower, but you can do it." Plus, keep training and pushing to your limit occasionally, and you'll keep your muscles - and your metabolism.

It comes down to this: Your metabolism won't slow down if you don't.

Fat Loss Article: Metabolism Myth  http://www.cbass.com/METABOLI.HTM