**Core Concept**
A high fiber diet has several health benefits, including reducing the risk of certain diseases. The underlying principle being tested is the relationship between dietary fiber intake and various health outcomes.

**Why the Correct Answer is Right**
A high fiber diet is known to reduce the risk of **coronary heart disease**, **type 2 diabetes**, and **constipation** by promoting satiety, improving blood lipid profiles, and regulating blood glucose levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because high fiber diets are associated with a lower risk of coronary heart disease.
**Option B:** Incorrect as high fiber intake helps regulate blood glucose levels.
**Option C:** Incorrect since a high fiber diet prevents constipation.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that a high fiber diet has numerous health benefits, but its impact on certain conditions like **gallstones** or **kidney stones** may not be as clear-cut, and in some cases, may even increase the risk.

**Correct Answer:** D. Gallstones.