这句话的主语是Murray,因此前面这句Hoping to be stronger to compete with the world's best在成分上只是一个从句,起修饰作用,当然动词要变ing形式,因为Murray has put on about 4 kg by eating句中has put on 是主动词,作谓语,前面的是附属成分（一个完整的句子中谓语只能有一个,不变hoping语法就错了） 这句话的句型很多见,类似的就像这句：Having to do so
much homework,I won't sleep early today.
twice as much as his usual翻译过来是：······是他平时/正常（水平）的2倍.usual的确是形容词,但此处his usual为省略形式,理解起来就当名词好了(o(∩_∩)o 哈哈,童鞋,不懂再问）