What is one permanent change you've made to create a life-long calorie deficit?

Making low-glycemic foods the mainstay of my menu.

Counting calories. I continue to count now that I'm trying a clean bulk and it keeps me focused. I hope I'll be able to do it forever if need be. I've made changes to my approach to food in placing mental value on calories. For example, I love bread, but for me, the calories in a couple of slices of bread just aren't worth it, given what else I could eat in it's place that would be just as many calories but much more satisfying and filling. Through counting calories and listening to my body I've also discovered how many calories it takes to keep me satisfied from morning to night. I could eat 1000 calories for breakfast but 400-500 easily keeps me satisfied from 8 am until 1 or 2 pm if need be. Lunch can be lighter, weighing in at 300-400 if need be but it often goes to 500 or more now. I'm quite content with 600-800 for dinner and that leaves me with several hundred to play with and even more on workout days. I never thought I'd ever have that kind of discipline when it comes to food but I do now, thanks to calorie counting.

Not ordering soda! I didn't really drink it at home, but when I went out to eat, I would usually get a coke. Now I only order water (if I want a drink of soda I steal a sip from my husband).

1. Eating more veggies, fruit, nuts, and lean protein while decreasing refined carbs. I still eat refined carbs but I consider them treats.
2. Finding an way to consistently make it to the gym 3 times every week.

Paleo / keto (15% sugar / carbs; 45% protein; 40% fat) and between 1500-1400 calories.

Started using a food scale.

Not drinking my calories. Its very rare I have soda, juice, or alcoholic beverages now.

Behavioral changes for me are:
1. Intermittent fasting. I generally do not eat before noon or after midnight and try very hard not to snack between meals. This naturally keeps my calories down.
2. Naturally gravitating towards veggies, healthy fats, and proteins. I'm currently in maintenance (temporarily) and working on reintroducing carbs and learning how to eat them in moderation. But I try to keep veggies, healthy fats and proteins as the cornerstones of my diet.
3. Exercise!! Especially strength and resistance training, because the more muscle you have, the more you can get away with, food-wise.
4. Eating home cooked foods.

Food changes are:
2. Sticking with low carb alternatives to popular high-carb foods. So cauliflower rice instead of rice, cabbage or shirataki noodles instead of pasta. Honestly, I don't generally miss pasta and I'm *kitten* at cooking rice, so this is something I will always keep up in my day to day life.
3. Not drinking my calories. If I want something sweet to drink, I'll have diet soda, unsweetened iced tea, or if I really really reallyyyyyyy want some juice, I will mix a few ounces of juice or nectar into seltzer water, to keep the calories and sugar low, but to still get the flavor.
4. Similar to the above, but avoiding alcohol. I now drink very rarely and will normally stick to liquor with a diet soda mixer. No beer, no wine, no mimosas or bellinis. I'm very partial to tropical mixed drinks, so if there is a good one available and I'm really feeling for it, I will let myself have it. I thought this would be hard because I used to drink alot but I don't miss alcohol and it saves a *kitten* ton of money, so this is a permanent change for me. Plus I live in a place where weed is legalized, so if I need to unwind, I just have a bit of that.
5. Switching from normal ice cream to an ice cream substitute. I love Halo Top, Enlightened, and Yasso the best. They are expensive, but worth every penny to someone with a crazy sweet tooth like myself.

I have been maintaining for years and have found that counting calories and weighing food helps termendously. Also not depriving myself of anything, if I have a night out and eat a high calorie meal of exactly what I wanted...so what...back to normal the next day.
Little things I have changed in my diet
-diet pop instead of regular soda
-lower sugar ketchup ( I pour ketchup over everything)
-splenda to replace sugar
-exercise!