I always order water when drinking out, not hot chocolate or pop.
Except for the occasional smoothie, I only drink a small glass of milk a day and lots of WATER, not living off fruit juice to quench my thirst like I used to.
I don't eat boxed junk desserts anymore, like Oreos or Twinkies. SERIOUSLY! They don't taste that good! If I'm going to be eating unhealthy dessert, at least give me some HOMEMADE PIE so it'll be worth it!
When we have pizza, I only get cheese and only take a slice or two, instead of getting pepperoni and taking tons.
I don't eat just because I FEEL like it, I eat because I genuinely need food, and if I am craving something I don't feed the craving, I go occupy my mind with something else instead.
I don't eat many dinners that don't have at least one green on the table, and I don't go very often without eating (usually snacking on!) fruit (kiwi and strawberries are UNGODLY good! I've gotten a reputation in my summer bio 101 class as being "strawberry girl." Somehow it's come up in conversation and much of the class is amused that I would take strawberries over steak, over candy bars, over french fries, over ANYTHING. I love them that much.

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I always eat mindfully and am aware of how much I should be eating, instead of eating until I am stuffed. I never eat till I am stuffed.
So that's just a few of the lifestyle changes I've made so far. I find all of them quite maintainable and I'm really enjoying my new healthy lifestyle!