为什么多饱都能再吃块甜点？研究：“甜点胃”有科学依据！

你是否有过这样“甜蜜的烦恼”呢？

“明明刚吃完火锅，看到提拉米苏却还能再战三百回合”。据说每个人都有两个“胃”，一个用来吃饭，一个用来吃甜点。无论吃得有多撑，永远有甜点的一席之地。

Have you ever pondered the phenomenon of consistently finding room for dessert when the dessert menu is presented? Researchers may have unraveled this mystery. The researchers at the Max Planck Institute for Biology of Ageing have discovered that the nerve cells responsible for inducing satiety post-meal also play a role in triggering sweet cravings following a meal.

大脑对甜食很“双标”

科学家们发现：人类对甜食的执念，竟是源于神经系统的“双重欺骗”。大脑中本该抑制食欲的关键神经元，在面对甜食时，却会刺激食欲，告诉大脑“我还能吃”。

德国马克斯·普朗克代谢研究所科研团队称，我们的POMC神经元具有“双重身份”。通常在我们吃饱喝足时，下丘脑中抑制食欲的神经元——POMC神经元，会被激活并发出“停止进食”的信号，就像在对身体说“别再吃了”。而即使吃饱了，在甜食面前，POMC神经元却会“背叛”身体，一反常态，改为促进释放β-内啡肽刺激进食欲望。

A report describes "a subset of neurons located in the hypothalamus—a deep brain region—that typically signal to us to stop eating post-meal. These neurons were found to drive sugar consumption in mice even post-satiation." Through brain imaging, researchers observed similar mechanisms in humans.

北京大学人民医院刘健教授解释：“β-内啡肽与大脑的奖励中心相互作用，制造愉悦记忆，让我们在吃甜食时觉得又开心又满足。这本质上是一种进化机制——在食物匮乏时期，促使人类优先获取高热量资源。”

甜食会改变我们的大脑

发表在《细胞代谢》期刊上的一项研究显示：高脂肪和高糖食物会改变我们的大脑。如果经常吃，即便是少量食用，未来大脑也会精准地提醒人们再次食用这些高糖高脂食物。研究人员解释：当人们天天食用高糖高脂食物后，大脑会建立连接，下意识地偏爱这些食物，更喜欢选择高脂高糖的食物。

Sugar overconsumption is one of the main drivers of poor health conditions such as obesity, Type 2 diabetes and cardiovascular disease. "What we choose to eat is controlled by our brain, but not all foods are equally 'rewarding' for the brain."

对甜食的偏爱“经久不衰”，和肠道神经也有关。 研究发现，一旦甜食进入胃肠道，肠脑轴就会被激活。肠脑轴是指肠道和大脑之间通过神经、内分泌和免疫等多种机制形成的双向交流系统，不仅调节着机体的消化、吸收、代谢等生理功能，还深刻影响着情绪、认知、行为等心理过程。肠道神经受到刺激，大脑随之释放摄入更多糖的信号，使“甜食偏好”持续存在。

如何科学有效克制“糖瘾”

《中国居民膳食指南(2022)》推荐，糖摄入量每天不超过50克，最好控制在25克以内。控制“糖瘾”，最好从以下5件事入手。

▌增加膳食纤维摄入

血糖波动正是引发糖瘾的元凶，而我们可以通过提高膳食纤维摄入来预防血糖骤升。常见的高膳食纤维食物有洋葱、大蒜、芦笋、苹果等。这些食物中的益生元纤维可通过改变肠道菌群直接影响大脑神经活动，使人体对甜食的渴望降低。

Research has also found that eating prebiotic fibre, found in foods like onions, garlic, asparagus and apples, causes changes in the gut bacteria that directly affect the brain, making you less likely to crave sugary foods. Switch to wholegrain bread, rice and pasta and leave the skins on potatoes for an immediate fibre boost.

▌足量摄入优质脂肪与蛋白质

每餐需确保优质脂肪与蛋白质的足量摄入。这两类营养素能在餐后显著延长饱腹时间、增加饱腹感，将对于饭后甜点的渴望降低。

Healthy fats, in the form of full-fat dairy, nuts, avocados and olive oil, and protein in nuts, eggs, fish and beans, are important in determining how satisfied you feel, so try to include them in every meal.

▌优先选用纯天然未加工的食物

超加工食品的成瘾性已获科学验证——食品制造商通过精确调控“糖-盐-脂肪”的黄金比例，刻意激活大脑愉悦中枢，这种令人欲罢不能的配比被称为“极乐点”（the bliss point）。研究表明，持续摄入超加工食品会使大脑奖赏系统敏感度降低，导致对天然甜味的感知阈值不断提高。

▌建立“正念饮食观”

营养师指出，大部分的甜食渴求实为情绪性进食。当人体处于压力状态时，皮质醇水平升高会触发对快速能量的需求，这种生理机制往往被误判为饥饿感。值得注意的是，情绪化摄入甜食后，有部分个体会产生自责情绪，反而加剧心理压力。

Try eating mindfully: we often eat a sugary snack because we are not tuned into our body's hunger signals. So before reaching for that biscuit, ask yourself these questions: How hungry am I on a scale of one to 10? If it's less than eight, you're not really hungry. Am I just bored or in need of a break? Perhaps have a cup of tea instead. Can I ride this out until the next meal?

▌吃甜点的时候，尽情地享受它

当选择享用甜点时，应当通过提升进食仪式感来获得更大满足，而非陷入“偷吃-愧疚”的恶性循环。研究显示，专注进食可提升多巴胺分泌效率，这意味着更小的分量就能获得同等的愉悦感。

Use a plate, sit down and enjoy your snack. You can make more nutritious sweet treats too. Have a square of dark chocolate with a teaspoon of nut butter to satisfy your sweet tooth in a more sustaining way. To put it simply, a holistic approach is the best way to deal with sugar cravings.

科学控糖没有捷径可走。坚持健康饮食、适量运动和保持良好心态，才是减少糖分依赖的最佳方法。

编辑：黎霈融

实习生：杨婧怡

来源：生命时报 阅外刊学英语

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