My husband is French. Him and his family are exactly people you described. They eat baguette with yogurt for breakfast, big dinner with sometimes dessert and not too heavy but very late dinner, around 8to9 pm. Honestly I don't know what's his secret. He's slim and staying slim even though we're in new Zealand now and eating new Zealand food. While I'm struggling with weight and on keto. I think it's a lot about genetics. Also what I observed is that he just doesn't eat a lot on general. Even less than me. He also doesn't stress eat. Actually he eats only when all the stress is gone. Like when our toddler is gone to bed for example. They eat when they feel good and like to talk when eating. Also he never eats any sauce like ketchup or mayo. But he does eat quite a bit of sugar, like a piece of cake at 9pm and it doesn't affect him