如何用英语讲：只有这样，才能让青少年健康茁壮成长

Only in this way can the youth grow stronger and healthier.注意半倒装，can 放在主语前

Only in this way can the youth grow healthily stronger.
注意倒装就行了。.:)

Only then, can let the young people health grow healthy and strong

only in this way can let youths grow up more healthy and sturdier.