Probably would have eaten less if he ate more slowly. There’s signal lag between when your body gets full and when it tells your brain this information. The slower you eat, the less lag there is between consumption and satiety signals to the brain. That’s why a lot of weight loss advise is “drink more water throughout the day” and “drink 20 oz of water 20 minutes before a meal”. It goes in the tank and sits there long enough for you to register it’s there.