A few quick ideas from my experiments are below. I'm not a doctor so these aren't recommendations -- just things that I've experimented with.
It requires a change in perspective. A quote I like is, "food is not a recreational drug." Food is fuel for a fermentation tank (digestive system). If you want the machine to run well, figure out what creates ideal fermentation environment. (Watch out for things like sugars and flours.)
I do meal prep by steaming a lot of vegetables in advance[1] and storing them in containers in the refrigerator. Then I can quickly make a variety of meals by combining the vegetables in various ways. Legume (bean, lentil, split pea) and vegetable soups are also good to have on hand at all times. Tahini is a base for a good sauce. I think 2 tbsp will provide about 10% of daily required calcium for most people.
When out of the house, I bring along some chunks of raw red cabbage and raw broccoli.[2] They are cheap, filling, and actually pretty good, especially when you're hungry. I think it's okay to skip meals when healthy food isn't available. Restaurants can also usually provide steamed, plain vegetables on request, if you're eating out with people.
Drink a quart of cold water before starting breakfast and sufficient water throughout the day.
If you need to reduce calories, you can make a cutoff time for eating -- like 4, 5, or 6 pm. That also provides 14-16+ hours of fasting per day to rest the digestive system. Another way to do it is to have reduced calorie days, like on the 5:2 diet.
When reducing calories I focus on high-nutrient foods. My main staple is steamed vegetables. I'd recommend becoming very familiar with different kinds of vegetables and how to cook them (steaming and/or adding to soups). A bookstore would probably have a selection of vegetable encyclopedia-type books.
If it seems hard to maintain a healthy diet, it's still easier than being sick. I went from 215 pounds to 145 pounds, hovering around 150.
Even if you don't reduce calories significantly, a diet focused on vegetables is probably going to have great long-term benefits, including life extension.
If you're in the Bay Area, and want to talk about ideas, you can come to one of our programming meetups.[3] I like to exchange ideas with other people who experiment with food. Or send me an email (josh@codeselfstudy.com), and I'll invite you to a place where I've posted more information about the experiments.
[1] https://codeselfstudy.com/files/food.jpg
[2] https://www.youtube.com/watch?v=zz4YVJ4aRfg
[3] https://codeselfstudy.com/