Simple diet and moderation on the Sabbath promote a clear mind for spiritual comprehension, whereas overeating dulls mental and spiritual perception.

Original passage

We should not provide for the Sabbath a more liberal supply or a greater variety of food than for other days. Instead of this the food should be more simple, and less should be eaten in order that the mind may be clear and vigorous to comprehend spiritual things. A clogged stomach means a clogged brain. The most precious words may be heard and not appreciated because the mind is confused by an improper diet. By overeating on the Sabbath, many do more than they think to unfit themselves for receiving the benefit of its sacred opportunities.