He often eats more than is good for his health.

1. more than 结构，可以按字面体会细节：吃的量多于对身体有益的量。那意味着：吃多了，不利健康。

2. 也可以干脆理解为“取舍关系”：than 之前的部分为“取”（肯定），之后为“舍”（否定）。例如：

The pain was almost more than he could bear. 那疼痛他几乎忍受不了。

I love you more than I can say.  我爱你，但口难开。