Good suggestions in here, but I'd like to back up a bit:
1) What do you want to accomplish with this change of diet/lifestyle? I read further back that you want to take a bit off the middle because you're not overall obese, is that correct? For that, I wouldn't recommend full-blown Atkins - firstly because it can be dangerous, second because it's really not fun for the first few weeks, and third because it's easy to yo-yo back.
If you want to tone/sculpt rather than lose weight overall, you'll want to add in some weight training too. If you have the motivation to treadmill, that's awesome (I still hate running). But also add some hand weight work and ab work (as well as stretching) - that will help develop your core and give you a better waistline.
I usually recommend that people I help keep a food diary for a few weeks. That lets them identify eating patterns and things that work/don't work. I recommend you start now if you haven't so you can re-assess in a couple weeks.
2) Crash dieting is bad. As others pointed out - drastic calorie reduction doesn't work very well because it's hard to sustain and, for dropping weight purposes, is counterproductive because your body freaks out and goes into conservation mode. You can actually lose more weight sustainably over time if you cut back 500 calories from your intake rather than 1000 (that's rough math - there is more specific math on how much to cut online).
3) Food balance. There's some new research out that suggests that both low-carb and low-fat diets can work because of how the liver metabolizes those macronutrients - it works better at one or another, but not both at the same time. So you can go with either to try (I believe that some genetic backgrounds work better with one or another), but remember that when you cut back on one thing, you'll be upping other things. I go with low(er) carb now, and I give myself more fat to compensate - for trimming fat off the middle, lowering carbs tends to be recommended because it's associated with insulin resistance (comes from too many carbs of all sorts).
Fat, salt and sugar make a triangle for flavor - if you cut one, you're increasing another. Check it out at the store: look at the nutrition for low-fat ranch dressing. It's much higher in sugar (and maybe sodium). Look at (oxymoronic) "fat free half and half" - it's loaded with sugar. This is why cutting fat across the board with "fat free" stuff makes things worse - you're burning out your insulin by consuming more sugar.
Here is why diet soda is bad: fake sugar fools your tongue, but not your brain because it needs glucose, and there is no glucose in fake sugars. So your brain goes, "Ah hah! You're giving me garbage that I can't use. I still need glucose to function! Go eat REAL sugar!" Then you still crave sweet stuff after having "sweet" food/drink. And now your body has gone into starvation mode because it didn't get what it needed and now is throwing a tantrum.
Also, the carbonation is bad. First, it expands your stomach, making it harder to feel full with the same amount of food. Small meals are good, but so is feeling full. Second, carbonation messes with your acid-base chemistry because the dissolved CO2 makes the liquid acidity, potentially leading to phosphorus and calcium being leeched out of your bones and teeth. Not good. Third, the carbonation makes it easier to digest food, letting you "cheat" and eat heavier stuff.
When I stopped drinking soda, I couldn't eat more than one large piece of pizza at a time or get heartburn. Heartburn is good - it means you've eaten enough. But when soda makes it easier to get that food down, you're taking in more stuff than your body can handle on its own.
4) Chewing food is good. This is more my own theory based on biology. Saliva helps to pre-digest food and start processing it so your body can absorb it better. I used to do smoothies, but over time I stopped because I'm suspicious of piping anything directly into my stomach without pre-processing. I suspect that this could lead to a worse insulin spike from the fruit sugar and some gas/bloating from the fiber not being processed. If you don't like fruit, then don't force yourself to eat it now. Stick with veggies (broccoli gives plenty of Vit C, for example) until you crave sweets, then fruit will be quite nice.
5) Respec your taste buds: If I were your health coach right now, I would take away your ranch dressing. Your taste buds get used to sweetness, salt, and fat and artificial flavorings and you need them to enjoy your food. But if you stop consuming those for 1-2 weeks, your taste buds reset and you don't need as much after. I know you're trying to find ways to enjoy veggies, but it could be counterproductive (and expensive) to go with the dressing, even if it's fat free (because it's high sugar). Steamed veggies (even microwaved) with a homemade vinaigrette and a shave of parmesan cheese adds a lot of flavor, good fats (use olive oil and lemon juice/apple cider vinegar), and no sugar. Acid accents flavors, and fat is good to help you absorb fat-soluble vitamins (A, D, E, K) from the veggies.
I'm happy to work with you on this - PM me if you're interested. I myself dropped 30lbs over 4 months (while in the Navy, so special circumstance) and have helped a friend drop 6 pants sizes over a couple months with moderate changes. I also love food, so I never scrimp on it; I just balance it properly so I know what my "dump stats" are.