High-Risk Scenario 1: When Early Life Undernutrition is Followed by Adult Weight Gain
The above text discussed the hypothesis that the fetus has a capacity to "anchor" its nutritional expectations to a gestational signal (e.g. hormones, nutrients) of average recent nutrition as experienced by the mother. This might allow the developing organism to modify its own nutritional expenditure, as reflected in its growth rate, body size and other traits, as locally experienced nutritional conditions change. It is easy to see how metabolic changes that could be favorable to a nutritionally stressed fetus or infant—such as sparing glucose or depositing more fat in the abdomen – might also plant the seeds for heightened risk of developing metabolic diseases if that individual ends up gaining weight during childhood or as an adult. Thus, any context in which individuals routinely face nutritional stress before birth or during infancy but then gain excess weight during later childhood or as an adult should be associated with a high susceptibility of developing metabolic disease. The now common finding that CVD risk is highest among individuals who were born small but later put on weight is consistent with this idea. Under what societal conditions might this pattern of early dearth followed by later excess be especially prominent or influential within a population? One way is as a result of rapid cultural, political or economic transition. In many societies, industrialization of farming is increasing affordability of cheap calories, while populations are also increasingly relying upon automobiles and other forms of transportation to move from place to place. As individuals take in more calories while expending fewer during the day, weight gain is inevitable. When the transition to relative caloric excess takes place within a single generation individuals raised under austere nutritional conditions during early life may go on to gain excess weight as older children or adults and have heightened CVD risk as a result. Consistent with this model, stunting – a measure of early life undernutrition—has been shown to be a risk factor for metabolic syndrome and obesity in populations experiencing rapid nutritional transition. Poor early life nutrition may also coexist with adult overnutrition simply because nutritional stressors are often concentrated during periods of heightened nutritional vulnerability early in the life cycle. In contrast to trends towards positive adult energy balance and weight gain in many global populations, the nutritional experiences of infants and young children are often more strongly influenced by common communicable diseases and their underlying social determinants, such as sanitation, crowding and the availability of clean water. That nutritional stress around the age of weaning is often severe is revealed by the mammalian strategy of depositing extra body fat after birth in preparation for weaning. Among mammals, humans give birth to the fattest babies on record, which may help us to prepare for this weaning stress, which is accentuated in our species owing to the need to provide a constant supply of energy for our unusually large and energetically fragile brains.
高风险场景1:当早期生活营养不良后,成年人体重增加上面的文章讨论了胎儿有能力将营养预期"锚定"的假设(如:荷尔蒙,营养),这是母亲所经历过的平均 近营养的表现.这可能会让发展中生物改变自己的营养支出,这反映在其生长速率、体型和其他性状上,因为当地有经验的营养状况会发生变化.很容易看到如何有利于代谢变化,胎儿营养强调或infant-such抽出葡萄糖或存放更多的脂肪在腹部——也可能植物的种子患代谢疾病的风险加剧,如果那个人 终在儿童或成年后体重增加.因此,在任何情况下,个体在出生之前或在幼年时期通常面临营养压力,但在以后的童年期或成年期,体重会增加过多,这应该与高度易感性的代谢疾病有关.目前常见的心血管疾病风险在出生时很小但后来体重增加的个体中是 高的,这与这个想法一致.在什么样的社会条件下,这种早期的缺乏和后来的过度在人群中特别突出或有影响?一种方法是快速的文化、政治或经济转型.在许多社会,农业的工业化正在增加廉价卡路里的负担能力,而人口也越来越依赖于汽车和其他交通方式,以从一个地方转移到另一个地方.随着人们摄入更多的热量,而在白天消耗的热量更少,体重增加是不可避免的.当在早期的生活中,在严峻的营养条件下,个体产生的相对热量过剩发生的时候,可能会随着年龄的增长而增加超重的体重,从而增加了心血管疾病的风险.与这一模型相一致的是,发育不良——一种早期营养不良的测量方法——已经被证明是在经历快速营养转变的人群中代谢综合征和肥胖的一个危险因素.早期的营养不良也可能与成人过度营养共存,这仅仅是因为在生命周期的早期,营养压力往往集中在营养脆弱的时期.与在许多全球人口中积极成人能量平衡和体重增加的趋势相反,婴幼儿的营养经验往往更强烈地受到公共传染病及其潜在的社会决定因素的影响,如环境卫生、拥挤和清洁水的供应.哺乳动物在出生后将额外的身体脂肪储存在准备断奶的过程中,这种营养压力通常是很严重的.在哺乳动物中,人类在记录中生下 胖的婴儿,这可能有助于我们为这种断奶的压力做准备,这种压力在我们的物种中更加突出,因为我们需要为我们异常巨大的、精力旺盛的大脑提供源源不断的能量.
It is an unfortunate fact that in many developing economies today, nutritionalstressors at this early age tend to be common—tracing to factors such as diarrhea and respiratory tract infections—despite the fact that those same individuals may later experience excess weight gain as adults. Because infancy nutrition remains tightly linked to social conditions related to poverty while the availability of cheap calories is increasingly common and driving adult weight gain, many individuals may how experience early life nutrition stress followed by adult caloric excess even in the absence of rapid societal transition. This is reflected, for instance, in the common co-occurrence of obese and malnourished individuals in the same household within some low-income populations. The body’s developmental response to early nutritional stressors can help to explain why these populations often have high rates of cardiovascular and other metabolic diseases.