I have been doing this in order to learn how much weight I immediately gain after a meal to actually learn how what I eat results in weight changes. Like eating 6 "meatless" chicken nuggets vs a slice or two of pizza and adjust accordingly to meet my daily target weight for the end of the night right before bed for healthy weight loss on a weekly basis. Portion sizes in the USA are so far different from reality that what you think is "one serving" is actually 2-3+ for a given meal, and I have had to completely rethink what a "healthy" portion size actually looks like for breakfast, lunch, and dinner.