燃烧吧，能量

• 岂能无怪哉

  2022-11-24
  动物园里的猿类食物充足却很少运动，它们会长得很壮实但不会发胖。它们的身体会把多余的能量用于瘦肉组织的生长，所以动物园里的猿类比野生猿类重很多，但体脂含量仍然不高。人类就不一样了，我们演化出了把多余的能量转变成脂肪的能力，用于应对未来可能发生的食物短缺、疾病或其他可能会降低能量供应的意外事件。现代社会和过去相比几乎是衣食无忧，这些意外可能永远也不会发生。然而，我们储存的脂肪远超身体所需，健康问题也随之而来。
• 岂能无怪哉

  2022-11-24
  坦白地说，我认为，如果片面地强调男性或女性的作用，就会忽视其中的真正原因。男性和女性在狩猎采集社会里扮演着必不可少的角色，没有哪个性别能独立存在。让狩猎采集社会如此成功的原因不是“狩猎”，也不是“采集”，而是“狩猎和采集”。我们不只是男性狩猎者或女性采集者，我们是分享者。现存的猿类和人类截然不同，它们几乎不会相互分享。当然，雌猿偶尔会把食物分给幼崽，野生的雌红毛猩猩大约每10顿饭会跟幼崽分享1顿。"这通常是因为食物很难获取，它们达不到人类“好妈妈”的标准。成年猿类之间的分享行为更少见，没人见过野生大猩猩分享食物。乌干达布东戈森林松索社区的成年黑猩猩每1~2个月分享一次食物，不过，这种所谓的“分享”更像默许的盗窃行为。虽然倭黑猩猩的分享频率更高，但它们的分享程度还是不如人类。日本研究员山本真也在刚果的万巴遗址发现，成年倭黑猩猩（大多是雌性）在14%的时间里会分享一种又大又新鲜的水果一曼氏阿诺木果。尽管猿类的一生都离不开复杂的社会关系，但它们在获取食物时总是独来独往。因此它们需要得到确定的结果，以保证自己每天都能吃饱；它们也没必要去追捕大型猎物，更没必要获取超过自己所需的食物。吃不完的食物，要么会浪费，要么会被没良心的同类顺手牵羊，以后也不会有所回报。黑猩猩和倭黑猩猩在大多数情况下，只有抓到猴子或霓羚（一种小羚羊）时才会与同类分享；万巴的倭黑猩猩则只会与同类分享曼氏阿诺木果，而且是在有同类来讨要食物的情况下。人类是社会性捕食者，通常会捕获超过自己所需的食物，目的就是分享给同伴。这种行为为我们构建了安全保障：即使一无所获的人也不会挨饿。分享行为激发了人类创新和承担风险的能力，从而发展出互助的觅食策略——狩猎和采集。狩猎时偶尔会捕获大型猎物，为群体成员提供了大量的脂肪和蛋白质；采集者则提供稳定可靠的食物，以免狩猎者运气不佳、一无所获。这种觅食策略...
• 岂能无怪哉

  2022-11-24
  无论新陈代谢和死亡之间的关系是出于偶然，还是有更深层次的原因，寿命和新陈代谢之间总是存在着奇怪而美妙的联系。心脏需要为身体组织提供足够的血液以传输营养物质和氧，心率和代谢率是正相关关系：小型动物心率快，大型动物心率慢。不过，由于小型动物比大型动物寿命短，不同物种的个体一生的心跳次数是相近的。从微小的鼩鼱到庞大的鲸类，它们一生的心跳都是10亿次左右。
• 闻夕felicity

  2022-11-21
  为了更好地理解利夫森的研究成果，我们得从身体这个巨大的蓄水池说起。人体就像一个湖，里面的水有进有出（人体内的水含量约为65%）。58氢原子、氧原子以食物和水的形式不断地进人人体，再以大小便、汗液、水蒸气的形式排出。利夫森的早期研究发现，氧原子还会以其他方式离开人体。当某种碳基分子代谢生成二氧化碳时，二氧化碳中的一个氧原子就来自人体这个蓄水池。我们呼气时，这个氧原子也会跟着离开人体。换句话说，氢原子只能以水的形式离开人体，而氧原子既能以水又能以二氧化碳的形式离开人体。利夫森意识到，如果他能弄清楚氢原子和氧原子如何离开人体他就能测量二氧化碳的产生速度。59另外，人体消耗能量时一定伴随着二氧化碳的呼出，因此，只要利夫森能测得二氧化碳的产生速度就能准确地测量人体的每日能量消耗。更奇妙的是，研究者不再需要把受试者关进代谢测量室里了。如果通过尿液可以测量氢原子和氧原子的排出速度，受试者想做什么就做什么。这个方法的难点就在于追踪人体内氢原子和氧原子的含量。利夫森想到了同位素，质子数量相同但中子数量不同的两个原子互为同位素。比如，正常的氧原子有8个质子和8个中子，而其同位素氧-18有8个质子和10个中子。氘是氢的同位素，前者有1个中子而后者没有中子。你每天饮用的水里有极其少量的同位素，它们通常都是无害的。利夫森在老鼠身上做实验，追踪氢原子和氧原子是如何离开它们的身体的。虽然同位素在老鼠身体里的表现和普通氢原子、氧原子一样，但利夫森可以将同位素作为标记物使用。如果老鼠在周一早上喝下含有10%的氢同位素的水，而到了周三只剩下5%，他就会知道从周一到周三老鼠体内有50%的含有氢同位素的水被普通水代替了。然后，他就能计算出有多少氢原子被排出体外了，他也可以用同样的方法计算出氧原子的排出速度，两者之间的差异还能反映出二氧化碳的产生速度。利夫森用同位素方法从老鼠身...
• 闻夕felicity

  2022-11-21
  世界卫生组织的营养学家用仪器测量了各种活动的能量消耗，并建立了估算日常能量消耗的方法。首先，根据一个人的体重、身高、年龄计算出他的基础代谢（使用前文讨论过的那类公式）。其次，搞清楚这个人的日常活动：睡了多长时间，走了多少路，坐了几小时，以及在其他活动上分别花了多长时间。每项活动都有对应的能量消耗，以基础代谢系数（体力活动比，英文缩写为PAR）来表示。体力活动比在本质上和表3-1中的代谢当量一样。结合每天的活动和这些活动的能量消耗，你就会知道这个人一天的能量消耗是基础代谢的多少倍。比如，假设某人一天睡了12小时（消耗10PAR）余下的12小时做家务（消耗20PAR），那么这个人24小时的平均能量消耗就是1PAR，也就是基础代谢的1.5倍。最后，把这个人的基础代谢乘以1.5就能估算出一天的能量消耗。这种方法叫作阶乘法，它并不精确，但得出的结果似乎挺可靠。世界卫生组织目前仍在用这种方法计算能量消耗。4另外，如果你在互联网上找到一个营养计算器，要求你输人身高、体重、年龄和体力活动，那它十有八九用的也是这种方法。阶乘法虽然已经问世几十年了，但它给出的结论的性质并没有改变：顶多算一种高质量的猜测。阶乘法对每日能量消耗的估算之所以看起来可靠，是因为基础代谢可以通过体型和年龄估算出来。而且，基础代谢占每日能量消耗的绝大部分，只要你能算对基础代谢，对每日能量消耗的估算就不会差得太多。可是，阶乘法有一个根本性的缺陷：它是建立在每日能量消耗等于基础代谢加上额外体力活动的能量消耗这个假设上的。这个观点已被广泛接受，以至于其他观点都没有立足之地了。每门营养学课程几乎都会这样教授，医学院也在用这种观点培养未来的医生，它还是很多健身和减重课程的指导思想。但事实上，能量消耗模式并非如此简单。特别是从长期看，能量消耗不是如此想当然地做加总计算即可，至少你的日常活动对能...
• JanusZzzzz

  2021-10-04
  Overconfident interpretation by shouty people who don’t know as much as they think they do has a name in science, the DunningKruger effect. In 1999, David Dunning and Justin Kruger, psychologists at Cornell University, had a brilliant insight that seemed to explain why incompetent people are so annoying: their very incompetence blinds them to how incompetent they areThe Hadza, Tsimane, and Shuar populations all get 65 percent or more of their calories each day from carbohydrates (compare that to less than 50 percent for the typical American diet; Diets among populations like the Hadza, Tsimane, and Shuar are also low in fat, which makes up less than 20 percent of their calories each day (the typical American diet is 40 percent fat).Diet and metabolism are such strong evolutionary driver...
• JanusZzzzz

  2021-10-04
  Burning more energy than you eat—what researchers refer to as negative energy balance—requires consuming your own bodyNotably, the men overshot their initial weight when they regained after the study, putting on a couple more pounds of fat than they had had at the start of the studyBMR and daily energy expenditure don’t dictate weight change, they respond to weight changeThe hypothalamus is the control center for your metabolism and a host of other housekeeping functions that keep your body aliveIf food restriction is severe and lasts for a long time, our organs will actually shrink. But not all organ systems are hit equally hard. We know from careful studies of the bodies of victims starved to death in war and famine that the brain is spared. The spleen, on the other hand, shrinks dra...
• JanusZzzzz

  2021-10-04
  And the variation in daily expenditure among couch potatoes was far greater than the difference between the average couch potato and the average high-activity adult.we’ve found that zoo-living primates have the same daily energy expenditures as those in the wild.daily energy expenditures and the PAL ratio have stayed the same in the United States and Europe for the past four decades, even as obesity and metabolic disease have skyrocketed.
• JanusZzzzz

  2021-10-04
  Somehow the Hadza, who get more physical activity in a day than the typical American gets in a week, were nonetheless burning the same number of calories as everyone else.
• JanusZzzzz

  2021-10-04
  Raise an ape in a zoo, with lots of food and limited exercise, and they get big but they don’t get fat. Their bodies use the extra calories to build more lean tissue, bigger muscles, and other organs. As a result, zoo apes weigh considerably more than they do in the wild, but they stay lean.
• JanusZzzzz

  2021-10-04
  Those with taller teeth survived longer, as it took longer for the teeth to wear out. After millions of years, long teeth became the norm for horses. (Which is why you can tell the age of a horse by looking in its mouth, to see how worn down its teeth are—a savvy move if you’re buying the horse, but rude if it’s a giftBehavior leads, form follows.It’s the human life history paradox: each kid takes longer to grow up, but we still manage to reproduce faster than our ape relatives. And it’s our commitment to sharing and unique metabolic strategy that make it work.
• JanusZzzzz

  2021-10-04
  Giving—sharing—isn’t a nicety among the Hadza. It’s the rule. Just like you don’t go around saying “Thank you for not spitting in my face” to everyone who doesn’t spit in your face, the Hadza don’t bother saying “please” and “thank you” for sharing. It would imply that the person is doing something beyond simply living up to the societal contractBut the crucial cognitive leap was not the hunting or the tools —after all, chimpanzees and bonobos hunt and make tools, and it hasn’t led to any radical departure from their ape-ish ways. The big dietary innovation that would change our metabolism and our evolutionary destinies wasn’t the food these hominins ate, it was the food they gave awayMore than just man the hunter or woman the gatherer, we are human the sharer.Humans are social foragers...
• JanusZzzzz

  2021-10-04
  Rather than concentrating all their reproductive effort over a few short years (where a bad year could wipe out most of your fragile offspring), primates had longer reproductive careers that lowered the consequences of encountering a poor season or twoAn apelike, plant-based diet, in turn, tells us these species didn’t need to walk very much to find food. It’s a general rule of ecology that plant-eaters don’t travel very far each day, because plants are plentiful and don’t run away. Living apes rarely cover more than a mile or two in a given day
• JanusZzzzz

  2021-10-04
  The bottom line is that your daily activity level has almost no bearing on the number of calories you burn each day.If 10 percent of the hydrogens in the subject’s body water were deuterium on Monday, but only 5 percent of them were deuterium on Wednesday, he would know that half of the body water from Monday had been flushed out and replenished with normal H 2O. He then could use those measurements to calculate the rate at which hydrogen atoms were lost. The same approach would tell him the rate of loss for oxygen atoms. The difference between those two rates had to reflect the rate of CO 2 production. Lifson’s mouse studies showed that isotopic measurements matched the CO 2 production measured by the metabolic chamber perfectlyThe best part was that subjects didn’t need to sit in a ch...
• JanusZzzzz

  2021-10-04
  the slower a species burns energy, the longer it tends to live(This is wrong)Coldblooded Greenland sharks can live four hundred year
• JanusZzzzz

  2021-10-04
  In each case, this radical metabolic acceleration was favored by natural selection because it increased energy for growth and reproduction. Mammals grow five times faster than reptiles and channel about four times more energy into reproduction. For reasons that still aren’t well understood, the cells of small animals work harder and burn energy faster than the cells of large animals. Each cell in a mouse burns ten times more energy each day than a cell in a caribou. Rates of growth and reproduction follow these same distinctive
• JanusZzzzz

  2021-10-04
  All birds and mammals have a thermoneutral zone, a range of environmental temperatures where body temperature is maintained without any effort. For humans, the thermoneutral zone is roughly between 75°F and 93The energy demand of fighting infection steals calories away from growth
• JanusZzzzz

  2021-10-04
  The kidneys also perform an important metabolic task called gluconeogenesis, converting lactate, glycerol (from fat), and amino acids (from proteins) into glucose.Neurons, the gray-matter cells that do the work of cognition and control, sending and receiving signals, do little of their own housekeeping. Instead, the glial cells (white matter), which outnumber the neurons nearly 10 to 1, do much of the support work, providing nutrients andBut while thinking is incredibly cheap, learning is quite energetically expensive.the brain accounts for over 60 percent of BMR, three times more than in adults. So much energy is channeled to the brain during these early critical years that it actually slows down growth in the rest of the body.
• JanusZzzzz

  2021-10-04
  You’d have to run about 3.5 miles to burn off the calories in a chocolate glazed donut (340 kcal) and more than eight miles to burn the equivalent of a large McDonald’s milkshake (840 kcal)
• JanusZzzzz

  2021-10-04
  We tend to think of oxygen as a good thing, the sustainer of life, but its true chemical nature is devastating. It steals electrons and binds to other molecules, altering them completely and often tearing them apart. Oxygen is Shiva the destroyer, obliterating everything it touches either slowly (rust) or violently (fire)Oxygen is the essential ingredient in oxidative phosphorylation precisely because it’s an electron thief—the characteristic that makes it so destructive