If you had a gastrectomy (removal of the stomach), your ability to absorb macronutrients would be severely impaired.

This statement is partially correct. A gastrectomy is a surgical procedure to remove part or all of the stomach. This can indeed affect the absorption of nutrients, but it's important to note that most of the absorption of nutrients actually occurs in the small intestine, not the stomach.

Here's a step-by-step breakdown:

1. The stomach's main function is to break down food and mix it with gastric juices to create a substance called chyme. This process is important for the absorption of certain nutrients like vitamin B12, which requires a specific factor produced by the stomach for its absorption.

2. After a gastrectomy, the chyme moves directly from the esophagus to the small intestine (depending on the type of gastrectomy). This can lead to a condition called dumping syndrome, where the chyme moves too quickly into the small intestine, leading to symptoms like nausea, vomiting, and diarrhea.

3. The small intestine is where most nutrient absorption occurs. It absorbs carbohydrates, proteins, fats, and most vitamins and minerals. If the small intestine is healthy and functioning, it can compensate for the loss of the stomach to some extent.

4. However, certain nutrients like vitamin B12, iron, and calcium may be harder to absorb after a gastrectomy due to the loss of specific factors and acids produced by the stomach that aid in their absorption.

5. Therefore, while a gastrectomy can impair the absorption of certain nutrients, it does not severely impair the absorption of all macronutrients. Patients who have had a gastrectomy will need to work with their healthcare provider to ensure they are getting the necessary nutrients, which may include taking supplements or modifying their diet.