If you like soda start drinking club soda. It's devoid of anything but CO2 and water (and by that I mean it probably also has carbonic acid in it) and while it tastes funny (because of the aforementioned carbonic acid) it provides the CRSIP SNAP of a soda without the... sugar. And it is ultimately just water, except the carbonation makes it a lot less heavy than just drinking a bottle of water, and the water logged feeling is why a lot of people don't tend to drink as much.
If you ARE going to drink soda, though, ditch the coke. Your body needs the good stuff, such as Reed's Ginger Ale. Organic soda's exist. They like, use pure cane sugar and lack sodium benzoate (Hint: Jones soda is not organic in the least, no matter what everyone things). Izze, which is more like a sparkling juice, is also a better choice.
Fruit juice wise, I rather like Bolthouse Farms. They can be rather high in sugar, but they're pretty vitamin rich from what I can tell. For instance, if you can stomach it, they have carrot juice, which has something like 700% the RDA of vitamin A per bottle.
Bottled tea is also an excellent idea. I don't recommend Arizona since that's pure sugar and I don't recommend Gold Peak because that tastes like water for chrissakes. Lipton is probably the best. Snapple's teas are usually flavored and sweetened, but have MUCH less sugar than soda or, say, Arizona. Well, the white/green/red teas. The normal lemon flavored iced tea is pure sugar. Read the labels, I guess.
Frozen and pouch and microwave dinners can be fine or awful depending on the brand. In general, read the label, and note that if it says something like HUNGRY MAN or if it has Kraft involved in anyway, just stay the hell away.
Amy's is excellent, both in quality and healthfulness -- they can be higher in sodium and cholesterol (if you get the cheese ones, which I recommend, as the tofu variants are... well, tofu freezes crappily) but they're quite lacking in additives and are all vegetarian so they're really nowhere near as bad as scarfing down Hungry Mans.
Cedar Lane also has some good choices. Again vegatarian and organic/all natural/whatever. No preservatives. They can be a bit less healthy and a bit less... good than Amy's.
Microwaveable curries are also a good suggestion. They come in a wide variety of packages, sometimes including rice. Usually they're in little airtight pouches and you can buy a bunch at a time and just store them underneath your bed for years at a time until you feel like eating them. This is an incredibly broad field though with a lot of variety in quality of taste, quality of healthfulness, and in general, everything. Always read the label. Swad, anything from Trader Joe's, Kitchens of India, Microcurry, and Tasty Bite are usually good bets.
For the record I don't recommend canned foods as they can take on the flavor of the can *quite* quickly which is entirely disgusting. There are a lot of healthy foods available in cans, but eh. Don't let them sit too long.
Moving on, depending on where you live, you'll have access to various brands of hummus. Hummus is good. Various brands vary in quality, though. One brand I love right now is, I believe, called Sabrosa. I'm also a big fan of Athenos. Keep in mind that hummus availability is really tied to location since the stuff doesn't ship well apparently (even though if left in a sealed tub that's never opened it can last well past its expiration date.)
Dairy stuff. Cheese is probably fine, but don't eat to much, and avoid greasier cheeses. I'd go with organic kinds, again, and avoid the hell out of Kraft. Sargento's not too bad, mostly. Horizon has excellent jack and cheddar, but the mozzarella leaves something to be desired. Yogurt... Dannon Naturals (coffe, vanila, and lemon flavored in the larger cups, four packs of various fruit flavors) or Stonyfield. Anything else has way too much artificial whatever. I'd also recommend trying out some various brands of Soy Yogurt. Soy Yogurt tastes nothing like real yogurt but can often times have a really good taste that's unique to it. Some brands just completely blow. Or rather, some flavors within the same brand blow. Notably, Stonyfield's peach flavored yogurt, that doesn't actually have any real fruit, just sucks immensely.
More than yogurt I'd recommend kefir if you can get it. It's usually available in jugs, drinkable, lower in fat, I believe, and has a higher bacteria count (which is good or something). I ALSO recommend using plain kefir instead of sour cream (similar in taste to plain yogurt, but sour, and it, like, pours, which makes it much more useful as a condiment than a large brick of sour cream or yogurt in the middle of your taco.
As far as fast food goes, I'd honestly recommend Chipotle, but without meat, sour cream, and guacamole (mostly because the guac costs a lot and they give you way more than you could rationally want). It tends to be rather high in calories, but it's also got a rather large amount of protein, and you're not going to be in a snacking mood for awhile. It leaves you full, basically, though I really recommend taking a walk afterwards. Qdoba's roughly the same thing.
Screw subway, no matter what they say. It's very low quality, not that healthy, and it's pretty much mostly bread and no protein and doesn't leave you feeling full. Just... sticky from the dressing dripping down your wrists and into your shirt sleeves :|
Healthy pizza is totally possible. Big recommendation is to ditch the meat and cheese. Cheese is not necessary at all. If the pizza no longer tastes good without cheese, it means the crust and sauce being used are inferior and you need to go somewhere else. Frankly my view on cheese on pizza is that it's only there to cover up either a lack of cohesion in the ingredients or a lack of quality.
Whole grain bread is a must. As a rule, though, avoid soft breads. They're not as good. Pepperidge Farms is pretty decent. If you have access to Ezekial 16:9 or whatever it is (you'll know it if you see it) go for that, because that's *really goddamn whole* grains and when I say "go for harder breads" that's basically what I mean.
Same for cereals. Ditch the Kellog's. Go off the beaten path and start finding new stuff. General advice though is that any cereal called twigs will be terrible. Look into cereals made from heritage grains like spelt and flax. For instance, Nature's Path makes this organic cereal called Flax Plus which ranges from expensive to affordable (get a bloody Kroger's Discount Card if you have a Kroger's near you. Seriously) and is quite amazing. Um, I'm also partial to Soy Milk. I don't think it's necessarily healthier than real milk (2% or whatever) but real milk just tastes immensely greasy to me. I'd go with Silk, though, as most brands are rather lacking in vitamins.
Just cooking plain grains, though? Barley is alright, rice is probably my favorite, pearled bulgar wheat is a close second. Millet? Not unless you like like the idea of eating something with the texture of a very large strawberry seed. Quinoa? Varies. I don't like it. Oatmeal? you can NEVER go wrong with outmeal.
Lentils, while not a grain, are awesome, as are chickpeas. Actually, beans. Okay. Peas are great. Not canned -- and no canned corn for that matter since it's awful. Corn and peas need to be fresh or frozen (although those curry pouches seem to maintain peas alright). Actually in general, any sort of bean or seed type vegetable is bad in a can (also, yes, biologically these are fruits. whatever). Tomatoes are great in cans, baked beans can actually work out okay (Depending on brand. Get the vegetarian kinds. The other ones have huge slabs of bacon in them. And try to get the reduced sugar sorts).
Chocolate's not bad, but go for higher... uh... darkness percentages. At least 70% and higher -- ie, not Hershey's. I doubt that, like me, you actually like the taste of baker's chocolate (I actually don't, but I do like the 99% thing Lindt makes which is roughly similar but... somehow palatable) but I think that most people can get used to the bitterness of 85% or so and enjoy it.
Someone recommended pineapples. I'd do that too, if only because you can start growing the tops relatively easily (which is another topic altogether but I could give you some pointers if you're interested, although in general, use rooting hormone, and remove every last shred of fruit from the foliage).
I'd really recommend cutting meat, I guess. Fish is probably fine, but at the least avoid steak and pork.
Uh, what else. Falafel is good, dolmadaki are good,
Also stay away from ramen. That stuff has zero nutritional value. Even plain ramen. Actually especially plain ramen.
And the biggest point of all, though: Don't eat way too much food. Eating sane amounts is perhaps the biggest issue to take note of. To the extent that if snacking throughout the day and avoiding large meals prevents you from just completely gorging yourself, then by all means, snack.
Someone also mentioned your body going into detox mode. This is true. It's also likely that if you start eating crap again after eating healthy for awhile, you'll get sick fast. Not, like, eating Wendy's fries (which aren't that bad compared to like, Burger King's. Frosty's also appear to be substantially better than actual ice cream but who knows. I'd avoid both really) a few nights out of the week amongst normally healthy eating wont, but a sudden and total dietary shift could -- say, like, vacation or something.
Also! General idea, and when I say you, I mean in a general sense: It's not so much that you're eating chocolate cake for desert every night. It's that you're eating chocolate cake for desert and meatloaf for your meal and a donut for breakfast and burgers for lunch.
And the idea that healthy food does not taste good is a massive bloody myth. After you get used to it you start realizing that coke pretty much does taste like chemicals and nothing like something actually edible.
Anyway though, for myself? A few years back -- actually, six I think -- I went from about 170 pounds down to 135 in a relatively short time, which probably wasn't healthy I guess but eh. What I did was dropping meat from my diet completely, drinking large amounts of diet soda (Bad idea. Diet soda is ++nongood. However the idea of getting rid of sugar-containing sodas remains), and cutting back my fat intake from something around 90... grams? 60? Whatever the RDA is to about 45 or so a day, and I believe 45 is rather on the low end so I wouldn't recommend something *that* drastic. Anyway, lowering fat intake, other things tended to follow (not necessarily sodium or sugar, but cholesterol and calories usually did). Um... In general my weight still sort of fluctuated (reaching a high-point of about 155 during my Junior year because I was eating nothing but chips and brownies for lunch because I couldn't really pack and they were the most edible things in the cafeteria, and dear god they were making me sick and I hated that) but losing the weight really wasn't any big issue at that point and it's remained pretty stably around 140/145 since then.
I should mention that being in college I get a ton of exercise from walking to class and also getting bored and being all "Hey I'll walk out to the mall" or "Hey there's a subdivision on the other side of town near the windfarm that I haven't been to yet. EXPLORATION TIME" and six miles later I have no idea where the fuck I am.