Losing weight may not be just about what you eatwhen you eat it according to a new study.

问题补充：

Losing weight may not be just about what you eatwhen you eat it, according to a new study.

A. so

B. and

C. but

D. for

答案：

A. so

B. and

(答案→)C. but

D. for

解析：句意：按照新的研究发现减肥可能并不只是关于你吃什么，而是你什么时间吃的。这里是not…but 不是……而是，not不和其他的词搭配，根据句意故选C。