Studies have shown that eating a really large breakfast helps with weight loss, because it helps you eat less the rest of the day (and especially at night). I think that’s one of the most important things you can do.
Most Americans get a huge proportion of their calories for animal products such as meat and cheese. Nobody did this before recent times, because it was too expensive (the Gemara talks about a rich man eating meat once a week, for example). If most of your calories come from other, less calorically dense foods — such as legumes, whole grains, vegetables and fruits — this will help with weight loss.
One food that is healthy, high in protein and is shown to make people feel full is buckwheat, which was an Eastern European staple food for hundreds of years. I like to cook buckwheat with lentils and eat it for lunch, along with some bread and an apple.