This is a question I get all the time and one I hesitate to answer in brief or in passing.
In short, you should eat healthy food a majority of the time, but healthy food means different things to different people and there is no one right answer for everyone. When I work with a client, the first thing I want to know is your goals and why you have those goals. Furthermore, are they achievable goals? Once that has been established, I like to know how much physical activity you participate in, what your food preferences are (likes, dislikes, cultural/religious preferences), and I also ask height, weight and age so I can determine how many calories you need based on your goals.
All of these factors are important and become even more so as you travel around the world. I’m constantly learning about different cuisines, food availability, and cultural norms. There’s local foods, and when you’re in a large city, like Bangkok, for example, every cuisine under the sun is available. In just my small area, there is Thai, Arab, Indian, Lebanese, Ethiopian (my favorite), and there’s even a Starbucks, Carl’s Junior, and Burger King in this building.
So, what should you eat? Considering most food preferences, cultural norms, and religious beliefs, most people should consume lean protein, plant based protein, a variety of fruits and vegetables, whole grains, healthy fats, and low fat and fat free dairy (if you consume dairy). These are general recommendations and you may choose not to eat some of these foods for certain reasons, but whatever you choose, make sure it’s nutrient dense and varied most of the time!