The amount of calories you eat in one meal does matter when it comes to body composition. The problem with excessively large meals has nothing to do with the speed at which food is metabolized, but rather the transient rise in insulin when compared to smaller meals (assuming frequency of meals remains static). Excessive stretching of the stomach (such as with a large meal) alone causes a rise in insulin secretion even on a low carb diet, although to a lesser extent than a high carb meal. 1000 cals in a meal is a lot. In the Anti-aging Zone Sears states that the average male only needs 1500 cals/day. Using this logic the poster on that thread was eating 2/3 of his calories needed for health in one meal. From personal experience, this is detrimental. You're body can metabolize as much food as you can put into it, it's just a matter of how those calories are metabolized. Grossly large meals tend to divert calories to fat storage rather than muscle and other important functions. Eat in moderation.
There are dreams we’re taught are normal, whether it’s money or success or any of those things, but we shouldn’t believe in those things if they are not important to us. There is an ocean between our real lives and what is expected of us.” -Tim Lambesis