Healthy and low calorie foods are not normally as quick to prepare as the fast food junk (eg you can't pick it up on the way back from work in 2 mins flat from Mc Donalds) but if you take some time aside maybe at the weekend to preplan and prepare meals in advance, you should be OK.
Maybe take saturday and sunday to prepare a very large meal which you can then put into small containers, freeze and have one by one during the week. Most things keep for 3 weeks at least, many keep for way longer. If you make say 5-8 portions a time, you will get to a point where you have many prefrozen meals and a great variety. (I used to do this at uni).
Some good examples of meals which are good to prepare in bulk and then freeze in portions are:
Bolognaise made with lean mince,
Curry made with chick peas or chicken
Chargrilled chicken breasts
Fish in a cream sauce (made with skimmed milk and lower fat options)
saag aloo potatoes and lentils
.....there are so many options- grab a recipy book.
Don't freeze rice, pasta, cous cous, things that have already been cooked from frozen and anything you chose to eat in the next 3 days.
What you do when you get home is just cook up a source of carbohydrates and if there is not one within the meal your re-heating, some vegetables. Cous cous, jacket potato, spaghetti, mashed potato, toast.... whatever you want.
Thats dinner sorted!
For lunch, its really about preparing stuff the night before. Sandwishes- you could do a similar mass-meal cooking thing and make a tuna-pasta with sweetcorn, dicec cucumber, sliced peppers and cherry tomatos. Add some lemon juice and you have a pasta dish for a good few days in your fridge. Other ideas could be chicken cous-cous with balsamic vinegar, chick-peas and diced vegetables and spices, sea-food pasta made with salmon, prawns, scallops, mussles..etc and olives, cherry tomatos, cucumber, green beans...etc
Only thing you can't save for a few days is rice. Its normally fine for like 24 hours but after that the rice grows bacteria at an alarming rate and could make you ill.
Breakfast: if you have the time, cereal is great, just be sure to weigh your cereal as its very easy to go overboard without realising: they use childrens bowls on the front of cereal boxes, there is no way what you see is 25 or 30g!
Porridge: whole rolled oats from the supermarket. Put 30g (or whatever you decide on) into a bowl, add dried peices of dried fruit for more fiber, (just make sure to calorie count it) cover with either milk or water and heat in a microwave for 2-3 mins. Keep an eye on yur bowl as if you have over filled it, the microwave will have it spill over the sides!
Rice cakes and cream cheese also make a nice breakfast. If you have the time, with a hard boiled egg sliced and tomato added is another option.
And if you have a good 20 mins, bakes beans on toast is a very filling and healthy option. Try to drink some orange juice or have an apple with that to balance it out as it otherwise has little in the way of fresh fruit and vegetables (the tomato sauce really isn't all that healthy despite having vitamin C in!)
The deal with losing weight is to have fewer calories going in then coming out so work out what your aiming for and then separate it out so you know what your able to eat within that.
Snacking between meals is fine too as long as you account for it. Try to stick to fresh fruit or vegetable sticks to keep the calories low.