One thing I know, for sure, is that I have to log my food to maintain my weight and I’ve been doing it for a few years. If I ate what I would like to eat, I would gain five pounds a month. I did gain five pounds in one week on a cruise and it took me a year to lose it.
I use MyFitnessPal, which is a free app with a premium version that gives you more data. It’s not perfect but it has one of the most comprehensive databases. You can also sync FitBit steps to MyFitnessPal and it will calculate calories burned.
Yes, it’s a chore but since people typically eat a lot of the same things, it becomes easier to log them in. Having a barcode reader in the app is the reason the whole process is doable. Most items at the grocery store have barcodes and MyFitnessPal has a database with the nutrition information.

If you want to repeat a meal, you enter Meals/Yesterday’s breakfast
When I first started using the app, the calorie count was eye-opening. At the end of the day, I didn’t have enough calories left for dinner but I was starving. I had to make changes to breakfast and lunch (and, of course, snacks) in order to make it through the day. My lunch sandwich had too many calories so I halved the condiments and chose different bread. I love a nice crunch with my sandwich so I want chips. In order to reach my goals, I can only have about 70 calories worth of chips, which is about 7 for the average tortilla chip. Now, my typical breakfast and lunch are on auto-pilot with choices that add up to roughly the same calories.
Eating out can be a nightmare but MyFitnessPal has menu items for most chain restaurants. You can also estimate what your meal contained and log it that way. A couple of years ago, I was at a conference and needed to eat lunch quickly. Red Robin Works was nearby and I ordered a cheeseburger and sweet potato fries. Unfortunately, I added up the calories after I ate them. The Red Robin cheeseburger is 880 calories and the sweet potato fries are listed as 470 calories with 25g of fat. There went most of my calories for the day and I still had 8 hours to go. I am more careful now when I’m at a restaurant searching for something that has less than 1,000 calories per meal!

When the barcode doesn’t bring up the nutrition information, food items can be added manually using “create a food.” You add the nutrition information from the label and save it with your custom name. I got this delicious sauce, which I have for an occasional treat, at Boa Vista Orchards in Apple Hill. It did have a nutrition label to use for the data.
I would suggest logging your food for at least a month to get into the habit. When you see what you’re eating, it may be enough to motivate behavioral changes. Is my diet perfect? No, absolutely not! But I have enough information to continue to improve it.