大家好，今天我們來聊聊“減肥產品”，分享兩個有代表性的：左旋肉鹼 & 奧利司他。
時間寶貴，先講結論：
對於普通健康人群，“靠吃左旋肉鹼減肥”是個謠言；
國內唯一非處方減肥藥奧利司他效果不佳還夾帶後患。
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
全文主旨講完了，不過還是希望大家能繼續聽我絮叨，畢竟斷章取義能瞬間得到很多結論，瞭解背後的原理才能建立自己的思考，對於任何科普在應用結論之前都記得先去分析邏輯過程。
成年人的世界除了長胖，其他的事情都不那麼容易。在物質富足的當下，與“超重”&“肥胖”&“身材不夠完美”捆綁的不僅僅是飆升的慢性疾病風險，還有日漸發酵的心理感受。
社交媒體大肆鼓吹“完美形象”，殊不知一個完美形象背後是一個團隊的共同製造。我們將自己的心理感受與外界評價捆綁，感覺自己有點胖，怎麼辦？小魚怎麼看我？小蝦怎麼看我？小蛤蟆怎麼看我？
這時候“減肥產品”以一種救世主的姿態入鏡：
配對比圖二三，震撼吧；（PS大法好，你懂的）
附學術文獻幾篇，有說服力吧；（數據質量如何不得而知）
提高代謝？增強飽腹感？阻止脂肪吸收？
純植物、純天然、八十幾道工藝提取，心動吧；
輪番廣告轟擊下讓你不下單都睡不著覺，這麼好的產品不試試總感覺自己損失了一個億啊。
當我們在討論“減肥藥”，我們到底在談論什麼？你是真的在掉體重，還是在浪費錢，甚至透支健康？
左旋肉鹼（L-carnitine）
相信減脂狗對於“左旋肉鹼”都不陌生，“左旋肉鹼能減肥”這種宣言滿天飛，你可能也買過“左旋肉鹼補劑”。
左旋肉鹼是啥？
是一種人體可以自身合成的氨基酸（*蛋白質分子的構件），除了自身合成外，飲食中的紅肉&魚&奶製品也富含左旋肉鹼，其中羊肉&牛肉是佼佼者。
因為能夠自身合成，並且飲食來源充分，普通健康人群並沒有缺乏左旋肉鹼的風險，而對於較為嚴格的素食主義者，以及一些具有特定遺傳疾病的人群確實有必要遵醫囑補充。
左旋肉鹼有啥用？
左旋肉鹼在體內的主要功能就是協助細胞將脂肪酸轉移到線粒體中，在線粒體中這些脂肪酸能夠被分解代謝從而釋放能量。
左旋肉鹼對於減肥有貢獻嘛？
理論上來看，挺可行的。畢竟人家能協助遊離在血液中的脂肪酸進入到線粒體中從而被代謝掉，多多補充多多消耗。
然而，聽起來可行是遠遠不夠的，人體是複雜的，合理的推導根本不能預測實際結果。而實際上，不論人體試驗或是動物實驗得到的結論也很有分歧。
在一項有38名女性參與的長達8周的實驗中，結果表明，是否服用左旋肉鹼對於減脂沒有明顯差異。
另一項對於“服用左旋肉鹼”是否有助於減脂的研究表明，志願者採用90分鐘的騎行運動進行為期4周的對照試驗，結果表明左旋肉鹼對於燃脂並沒有幫助。
然而，在一項綜合了9項研究的報告中表明，平均來看服用左旋肉鹼的志願者相比於對照組實現了多減重1.3kg，而這些試驗主要在肥胖人群&較為年長的人群中開展。
總體看來，服用左旋肉鹼對於普通人群並沒有什麼減脂效果。
當選擇合適的飲食並結合運動的時候，服用左旋肉鹼能夠提升肥胖症人群&較為年長的人群的減脂效果；
而對於年齡較小&活動度較高的人群是否有相同的效用依舊沒有足夠的數據支撐。
奧利司他（Orlistat），“躺瘦”的希望之光？？
奧利司他是種為了治療肥胖症而設計出來的藥物，通過抑制脂肪酶活性來妨礙飲食中的脂肪代謝，從而降低卡路里的吸收。
這是國內市場上唯一一種非處方的減肥藥，是的，人家是正正經經的減肥藥，合法。聽起來很完美是吧，不用管住嘴邁開腿，躺著就能瘦。
奧利司他效果如何？
哎嘿，然並卵，海量臨床數據顯示在改變了生活方式的基礎上（*是的，控制飲食&運動是必須的，失望了吧哈哈哈），吃藥的人相比於對照組在1年中多減重2-3kg。減過脂的人都知道吭哧吭哧的1年下來才多掉了5斤，“性價比”也是忒讓人失望了。
負作用
奧利司他的副作用也非常“可觀”。會引發胃腸道的不良反應包括脂肪性腹瀉（steatorrhea, oily, loose stools）等，同時也有報道表明服用奧利司他會影響脂溶性維生素的吸收。
並且美國食品及藥品管理局（FDA）發出警告，奧利司他存在肝損傷風險 。所以呢，合法的非處方藥物尚且如此，效果不佳還夾帶後患，其他的更是可想而知。用藥需謹慎，請諮詢醫生根據自身狀況慎重選擇。
其實多數時候“好身材”的呈現是背後的健康狀況和良好生活習慣的副產品，要是本末倒置，那可就太不酷了。
本文僅是針對左旋肉鹼&奧利司他的科普，這兩種都是合法的運動補劑或藥品，如有自身需求請諮詢醫生後謹慎選擇。文章作者不承擔任何責任。
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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