可以用 "Takeout can cause obesity" 表示外卖会导致肥胖。

这句话的来源是由于外卖食品通常含有较高的热量和较低的营养价值，因此食用过多的外卖食品可能会导致超重和肥胖。

下面是一些英文例句及其中文翻译：

"Eating takeout regularly can contribute to weight gain and obesity." (经常吃外卖会导致体重增加和肥胖。)
"One of the main factors contributing to the obesity epidemic is the increase in the availabipty and consumption of fast food and takeout meals." (导致肥胖流行的主要因素之一是快餐和外卖食品的普及和消费增加。)
"Research has shown that people who rely on takeout and fast food are more pkely to be overweight or obese than those who cook at home." (研究表明，依赖外卖和快餐的人比在家做饭的人更容易超重或肥胖。)