I think the biggest thing is your will power and sticking to not snacking (unless that's part of your diet (i.e. 6 meals per day) or something like that). Every time I've been very specific w/my diet it's helped tremendously, and when I get off of tracking and let 1 cheat day slip to 2 or 3, that's when the weight comes back. I had a TON of success w/the Tim Ferris 4 hour body diet when I was eating a lot of chicken and eggs, I dropped a ton of weight, but also was eating almost no carbs which did tend to lower my energy, especially as I exercise, but I've neve dropped more weight than I did on that diet, and I got 1 full cheat day where I could go crazy, which was fun!
I went vegan 3 years ago, which was a big change from the 4 hour body plan which I was doing at the time, but it was a "challenge" from DW, and w/in 3 days I noticed significant reduction in swelling in my knee which I've had problems with, so I stuck with it since then and have not looked back. I dropped weight from going vegan and feel a lot better!
Then about a year ago I started doing intermittent fasting, I started w/eating between the hours of 12PM-8PM and dropped a lot of weight as well. I thought it would be impossible as I used to eat a huge bowl of oatmeal at 6AM when I woke up. I found that after the meal time I would normally eat was over, that my body felt like any other time, so after the "growlin" period was over I was just fine. Initially to adjust I would drink a ton of water which filled me up, but now it's just very normal, and I have cut down my eating window to maybe 7 hours (between 1 or 2PM at 7 or 8PM).
I have cheated a lot during the holidays, so lots of sugar and vegan cookies, so I've put on a few pounds, but I've been successful w/the intermittent fasting, and it works really well for me b/c I don't great will power regarding the portions, so I find that if I'm regimented that it works the best for me. So I don't call it a "diet" but just the way I eat now.
When I fall off the wagon and start snacking or eat sugar at night then I gain weight, when I don't snack and stick to the normal meal plan then I drop weight. I tracked calories for a while when I was trying to cut, and it was actually really cool going to bed and knowing that you would be half a pound lighter in the morning.
I think it all just depends what works for you as a lifestyle change, for some it's more exercise, better diet, the same meal plan, etc. For me it's sticking w/the same meal plan for the most part, a schedule and not snacking at night.