It is easy for an American person new to Ireland to see that people are generally thinner than in the U.S. I often disagree with Irish people on what is considered “overweight”. While I think a person is of average or slightly overweight, an Irish person calls him or her as “fat”.
While living in Ireland, I have been observing the culinary habits of Irish people and my conclusion is that they eat much less than Americans. The most noticeable thing is that Irish people often eat a sandwich, a plate of salad, or a bowl of soup for lunch and a nice big meal in the evening. If they eat a big meal or “dinner” at 1:00 p.m., then they eat a light meal called “tea” that constitutes one of the above mentioned options for dinner.
This is in contrast to how I used to eat in the U.S. I would have a nice plate of spaghetti for lunch and a nice plate of half of rotisserie chicken for dinner. This amount of food would constitute as eating two dinners per day and would not be approved by most Irish people. Since I have moved to Ireland, I think that my lunch portions have decreased. Whereas I never ate a sandwich back home, I now eat a simple sandwich with ham and cheese or eat a bowl of salad for lunch.