Some people swear that smoking cigarettes keeps them slim.

But being exposed to cigarette smoke can actually make people pile on the pounds, new research shows. 

And it is innocent victims of secondhand cigarette smoke are the most likely to gain weight.

'For people who are in a home with a smoker, particularly children, the increased risk of cardiovascular or metabolic problems is massive,' said lead author Professor Benjamin Bikman, of Brigham Young University in Utah.

Passive smoking damages the body because second-hand smoke contains more than 4,000 chemicals, many of which are irritants and toxins, and some of which are known to cause cancer.

Data shows half of the U.S. population is exposed at least once daily to secondhand cigarette smoke and approximately 20 per cent of young children live with someone who smokes in the home.

In the UK, it's estimated that second-hand smoke kills over 12,000 people every year from lung cancer, heart disease, stroke and the lung disease Chronic Obstructive Pulmonary Disease (COPD).

Professor Bikman, and his co-author Professor Paul Reynolds, wanted to investigate how cigarette smoke is tied to metabolism.

參考譯文：
吸煙和二手煙的危害早已經廣為人知。

有人聲稱吸煙可以幫助減肥。一項新研究結果證明，吸煙不但不能幫助減肥，反而可致肥胖，而二手煙受害者更為顯著。

美國猶他州楊百翰大學的本杰明Bikman領導的團隊通過實驗研究找到了吸煙引發胰島素抵抗，從而導致體重增加的機制。在研究中，他們讓小鼠暴露于二手煙來分析了它們的代謝進程，并得到了預期的結果——暴露于煙霧中的小鼠長胖了。

研究人員進一步在細胞水平上分析發現，煙霧觸發一種被稱為神經酰胺的微小脂質改變細胞中的線粒體，這造成正常細胞功能障礙，并抑制細胞對胰島素的響應能力。也就是說，被動吸煙可改變身體對胰島素的敏感性，造成胰島素抵抗，導致身體需要更多的胰島素。胰島素水平的升高則導致身體脂肪的集聚形成肥胖。

研究人員發現，逆轉香煙煙霧這種影響的關鍵是抑制神經酰胺。進一步研究發現，用一種已知神經酰胺阻滯劑——多球殼菌素治療的小鼠，無論是否暴露于煙霧，均沒有出現代謝問題和肥胖。然而，當暴露于煙霧的小鼠同時喂食高糖飲食，代謝干擾則不能被防止。

Bikman教授和他的團隊正測試神經酰胺酶抑制劑在人體使用的安全性問題。

研究者表示，有希望開發一種為無辜的二手煙受害者提供保護的治療措施。但是對于吸煙者本人卻沒有“保護療法”可用，他們唯一可以做的就是戒煙。這或許會給癮君子提供戒除煙癮的一種新動力。