So firstly dispose of any and all snacks which are processed from your diet. Yes I do mean all. Crisps (or chips as their known in the state), bars of chocolate, those little packs of cheap cooked "meat" that are easy to eat through, remove it all. Beyond the clear nutritional problems these things cause, you have the fact that they are *too* easy to eat, they are too tempting. This goes for whether you are fat or slim, they contain very little good for you beyond maybe some protein in the meat and even then they will usually contain other negative attributes that counter that. Luncheon meats such as pepperoni and chorizo are passable to keep but even those must be eaten in moderation.
Moving onto the main components of a dinner, you also need to drop *all* processed meats, all of them. If you wish to eat meat then buy fresh, it's quite simple really. A good bit of chicken or beef will last a few days in the fridge and can be easily prepared within under half an hour with your own seasoning and garnish. There are a great many perks to switching to fresh, firstly nutrients will be higher, secondly you know the process of preparation for you yourself are doing it therefore no additional additives or chemicals, thirdly cooking is a vital and easy skill to attain. Yes one must be mindful of the type of fresh meat he buys for even this can contain hormone injections and the like, a good method is to bite the bullet and seek grass fed or organic meat. It is a bit more expensive but then this is a proper meal, you *must* get out the mindset of cheap and easy for that is what is trapping you. If your working on a budget a good method I used to use would be visiting the supermarket rather than a dedicated butcher an hour or two before closing when the remaining good cuts or packs are reduced, buying a decent amount of the good stuff, storing enough in the fridge to last a time then freezing the rest for later, it saves money and saves further visits to a supermarket. If your finding meat is close to going off consider a stew and leave it to slowly simmer over night or some such, there are many inventive ways to use meat even if it's just before it's going to turn. Also when cooking meat while oil is fairly common consider switching to either extra virgin olive oil or a decent quality butter (actual butter, not the horrible pretenders you get in supermarkets). Both have higher burning points and more nutrients in the case of butter. Rapeseed and it's cohorts is a hipster meme, don't even bother with it.
Fresh vegetables are usually a fair bit better than frozen but the frozen can work decently if in a pinch, they sometimes lose their flavour and nutrients a tad in the time between chopping and freezing in the factory compared to freshly cut ones but for the most part they *should* be untampered. I use a fair bit of frozen garlic and onion for my cooking due to the expediency and the fact it has nothing added, it's a good choice although I find the garlic can lack the oomph of freshly crushed.