大家好，今天我们来聊聊“减肥产品”，分享两个有代表性的：左旋肉碱 & 奥利司他。
时间宝贵，先讲结论：
对于普通健康人群，“靠吃左旋肉碱减肥”是个谣言；
国内唯一非处方减肥药奥利司他效果不佳还夹带后患。
https://www.nhs.uk/news/obesity/new-diet-pills-qa/
https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/020766s035lbl.pdf
Padwal RS, Rucker D, Li SK, Curioni C, LauDCW. Long-term pharmacotherapy for obesity and overweight. Cochrane Database ofSystematic Reviews 2003, Issue 4. Art. No.: CD004094. DOI:10.1002/14651858.CD004094.pub2.
Theeffectof(L-)carnitineonweightlossinadults:asystematicreviewandmeta-analysisofrandomizedcontrolledtrials.ObesRev.2016
https://www.nhs.uk/news/2011/05May/Documents/BtH_supplements.pdf
https://www.ncbi.nlm.nih.gov/pubmed/10861338
https://www.ncbi.nlm.nih.gov/pubmed/16521850
https://www.ncbi.nlm.nih.gov/pubmed/27335245
https://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm213038.htm
全文主旨讲完了，不过还是希望大家能继续听我絮叨，毕竟断章取义能瞬间得到很多结论，了解背后的原理才能建立自己的思考，对于任何科普在应用结论之前都记得先去分析逻辑过程。
成年人的世界除了长胖，其他的事情都不那么容易。在物质富足的当下，与“超重”&“肥胖”&“身材不够完美”捆绑的不仅仅是飙升的慢性疾病风险，还有日渐发酵的心理感受。
社交媒体大肆鼓吹“完美形象”，殊不知一个完美形象背后是一个团队的共同制造。我们将自己的心理感受与外界评价捆绑，感觉自己有点胖，怎么办？小鱼怎么看我？小虾怎么看我？小蛤蟆怎么看我？
这时候“减肥产品”以一种救世主的姿态入镜：
配对比图二三，震撼吧；（PS大法好，你懂的）
附学术文献几篇，有说服力吧；（数据质量如何不得而知）
提高代谢？增强饱腹感？阻止脂肪吸收？
纯植物、纯天然、八十几道工艺提取，心动吧；
轮番广告轰击下让你不下单都睡不着觉，这么好的产品不试试总感觉自己损失了一个亿啊。
当我们在讨论“减肥药”，我们到底在谈论什么？你是真的在掉体重，还是在浪费钱，甚至透支健康？
左旋肉碱（L-carnitine）
相信减脂狗对于“左旋肉碱”都不陌生，“左旋肉碱能减肥”这种宣言满天飞，你可能也买过“左旋肉碱补剂”。
左旋肉碱是啥？
是一种人体可以自身合成的氨基酸（*蛋白质分子的构件），除了自身合成外，饮食中的红肉&鱼&奶制品也富含左旋肉碱，其中羊肉&牛肉是佼佼者。
因为能够自身合成，并且饮食来源充分，普通健康人群并没有缺乏左旋肉碱的风险，而对于较为严格的素食主义者，以及一些具有特定遗传疾病的人群确实有必要遵医嘱补充。
左旋肉碱有啥用？
左旋肉碱在体内的主要功能就是协助细胞将脂肪酸转移到线粒体中，在线粒体中这些脂肪酸能够被分解代谢从而释放能量。
左旋肉碱对于减肥有贡献嘛？
理论上来看，挺可行的。毕竟人家能协助游离在血液中的脂肪酸进入到线粒体中从而被代谢掉，多多补充多多消耗。
然而，听起来可行是远远不够的，人体是复杂的，合理的推导根本不能预测实际结果。而实际上，不论人体试验或是动物实验得到的结论也很有分歧。
在一项有38名女性参与的长达8周的实验中，结果表明，是否服用左旋肉碱对于减脂没有明显差异。
另一项对于“服用左旋肉碱”是否有助于减脂的研究表明，志愿者采用90分钟的骑行运动进行为期4周的对照试验，结果表明左旋肉碱对于燃脂并没有帮助。
然而，在一项综合了9项研究的报告中表明，平均来看服用左旋肉碱的志愿者相比于对照组实现了多减重1.3kg，而这些试验主要在肥胖人群&较为年长的人群中开展。
总体看来，服用左旋肉碱对于普通人群并没有什么减脂效果。
当选择合适的饮食并结合运动的时候，服用左旋肉碱能够提升肥胖症人群&较为年长的人群的减脂效果；
而对于年龄较小&活动度较高的人群是否有相同的效用依旧没有足够的数据支撑。
奥利司他（Orlistat），“躺瘦”的希望之光？？
奥利司他是种为了治疗肥胖症而设计出来的药物，通过抑制脂肪酶活性来妨碍饮食中的脂肪代谢，从而降低卡路里的吸收。
这是国内市场上唯一一种非处方的减肥药，是的，人家是正正经经的减肥药，合法。听起来很完美是吧，不用管住嘴迈开腿，躺着就能瘦。
奥利司他效果如何？
哎嘿，然并卵，海量临床数据显示在改变了生活方式的基础上（*是的，控制饮食&运动是必须的，失望了吧哈哈哈），吃药的人相比于对照组在1年中多减重2-3kg。减过脂的人都知道吭哧吭哧的1年下来才多掉了5斤，“性价比”也是忒让人失望了。
负作用
奥利司他的副作用也非常“可观”。会引发胃肠道的不良反应包括脂肪性腹泻（steatorrhea, oily, loose stools）等，同时也有报道表明服用奥利司他会影响脂溶性维生素的吸收。
并且美国食品及药品管理局（FDA）发出警告，奥利司他存在肝损伤风险 。所以呢，合法的非处方药物尚且如此，效果不佳还夹带后患，其他的更是可想而知。用药需谨慎，请咨询医生根据自身状况慎重选择。
其实多数时候“好身材”的呈现是背后的健康状况和良好生活习惯的副产品，要是本末倒置，那可就太不酷了。
本文仅是针对左旋肉碱&奥利司他的科普，这两种都是合法的运动补剂或药品，如有自身需求请咨询医生后谨慎选择。文章作者不承担任何责任。
附：全文英文版（English version）
L-Carnitine
L-carnitine is a naturally occurring amino acid derivative that's often taken as a supplement.
It is used for weight loss and may have an impact on brain function.
However, popular claims about supplements do not always match up with the science.
This article examines the potential risks and benefits of L-carnitine supplements and explains how this nutrient functions in your body.
What is L-Carnitine?
L-carnitine is a nutrient and dietary supplement.
It plays a crucial role in the production of energy by transporting fatty acids into your cells' mitochondria.
The mitochondria act as engines within your cells, burning these fats to create usable energy.
Your body can produce L-carnitine out of the amino acids lysine and methionine.
For your body to produce it in sufficient amounts, you also need plenty of vitamin C.
In addition to the L-carnitine produced in your body, you can also obtain small amounts by eating animal products like meat or fish.
Vegans or people with certain genetic issues may be unable to produce or obtain enough. This makes L-carnitine aconditionally essential nutrient.
Role in your body
L-carnitine's main role in your body involves mitochondrial function and energy production.
In cells, it helps transport fatty acids into the mitochondria, where they can be burned for energy.
About 98% of your L-carnitine stores are contained in your muscles, along with trace amounts in your liver and blood.
L-carnitine may help increase mitochondrial function, which plays a key role in disease and healthy aging.
Newer research illustrates the potential benefits of carnitine's different forms, which may be used for various conditions, including heart and brain diseases.
Does it aid weight loss?
In theory, using L-carnitine as a weight loss supplement makes sense.
Since L-carnitine helps move more fatty acids into your cells to be burned for energy, you might think this would increase your ability to burn fat and lose weight.
However, the human body is extremely complex, and the results of both human and animal studies are mixed.
In an eight-week study in 38 women who exercised four times per week, there was no difference in weight loss between those who took L-carnitine and those who did not.
What's more, five of the participants taking L-carnitine experienced nausea or diarrhea.
Another human study monitored L-carnitine's effect on fat burning during a 90-minute stationary bicycle workout. Four weeks of taking supplements did not increase fat burning.
However, one analysis of nine studies — mostly in obese individuals or older adults — found that people lost an average of 2.9 pounds (1.3 kg) more weight while taking L-carnitine.
More research is needed to confirm the benefits of L-carnitine in a younger, more active population.
While it may aid in weight loss for obese individuals or older adults, a thorough diet and exercise regimen must be in place first.
What is Orlistat ?
Orlistat is the over-the-counter version of apharmaceutical weight loss drug called orlistat.
This drug was first approved by the FDA in 1999. It is usually prescribed for long-term obesity management, alongside alow-fat, calorie-restricted diet.
How does Orlistat work?
Orlistat works by preventing the body from absorbing dietary fat.
Specifically, it blocks an enzyme in thegut called lipase.
Lipase is essential to the digestion of the fats we eat. It helps break down fats into free fatty acids that can be picked up by the body.
Without this enzyme, dietary fat bypasses digestion and is then expelled from the body.
As a lipase-inhibitor, Orlistat has been shown to reduce the absorption of dietary fat by about 30%.
Because dietary fat is high in calories, this leads to fewer calories being processed by the body, which can lead to weight loss.
Orlistat can help you lose small amounts of weight
Several large human studies have been conducted on orlistat, the active compound in Alli diet pills.
The most well-known is the Swedish XENDOS study, which included 3,305 overweight individuals and lasted for 4 years.
There were two groups in the study. Onetook 120 mg of Orlistat, three times daily, while the other group took aplacebo.
All participants were instructed to eat 800 fewer calories per day, and limit dietary fat to 30% of calories. They were also encouraged to go for walks every day.
Do Orlistat work? An evidence-based review
Orlistat works by preventing the body from absorbing dietary fat.
Specifically, it blocks an enzyme in the gut called lipase. Lipase is essential to the digestion of the fats we eat. It helps break down fats into free fatty acids that can be picked up by the body.
Without this enzyme, dietary fat bypasses digestion and is then expelled from the body.
As a lipase-in hibitor, Orlistat has been shown to reduce the absorption of dietary fat by about 30%. Because dietary fat is high in calories, this leads to fewer calories being processed by the body, which can lead to weight loss.
Orlistat interrupts the digestion of dietary fats and blocks about 30% offat from being absorbed. This leads to an overall reduction in calorie intake.
Orlistat Can Help You Lose Small Amounts of Weight. Several large human studies have been conducted on Orlistat, the active compound in Alli diet pills.
The most well-known is the Swedish XENDOS study, which included 3,305 overweight individuals and lasted for 4 years.
There were two groups in the study. One took 120 mg of Orlistat, three times daily, while the other group took aplacebo.
All participants were instructed to eat 800 fewer calories per day, and limit dietary fat to 30% of calories. They were also encouraged to go for walks every day.
During the first year, the average weight loss in the orlistat-treated group was 23.3 pounds (10.6 kg), while the place bogroup lost only 13.6 pounds (6.2 kg).
According to this study, Orlistat combined with diet and exercise may make you lose almost twice as much weight as dietand exercise alone.
Side effects, dosage and how to use
Orlistat diet pills do have somewell-documented side effects that are worth noting.
As they block fat absorption, the presenceof undigested fat in the bowel can cause digestive symptoms, such as abdominalpain, diarrhea and flatulence.
Some people also experience fecal incontinence and loose, oily stools.
Continued use of Orlistat can also impairthe absorption of fat-soluble nutrients like vitamins A, D, E and K. For this reason, taking a multivitamin along with treatment is recommended.
Orlistat may also interfere with the absorption of some medications, and a few cases of liver failure and kidney toxicity have been reported.
People who are taking medications or have any sort of medical condition should consult with their doctor before taking Orlistatdiet pills.
Based on the limited long-term data available, most clinical guidelines recommend that Orlistat is not used continuously for more than 24 months. The optimal dosage used in the studies is 120 mg, three times per day.
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