No junk food's good. Just don't skimp too much on protein. Your body'll need it, along with the very healthy vegetables and fruit.
I was slightly anemic, so before surgery I consciously changed my diet to include iron-rich food sources. I also took iron as prescribed by my OS, but I was really glad when he let me stop taking it, as the pills (along with the 325mg coated aspirin) were doing quite the number on my tummy.
I was really trying to eat healthily before my surgery, including dietary sources of iron.
Meats I added: beef, liver,* clams, oysters. Meats I was already eating: dark poultry, lamb, shrimp, tuna, occasional ham, mackerel,** liverwurst. Meats I didn't find the heart or stomach for: beef hearts, kidneys.
Whole eggs, including the yolk.
Legumes etc. I was already eating: lentils, soybeans, dried beans, etc.
Whole grains
Nuts: apparently almonds and brazil nuts are good sources, as are pumpkin seeds and sesame seeds
Dark leafy greens (especially a good source when eaten with a good source of vitamin C like tomatoes, peppers, strawberries, oranges, etc. -- in fact, eating non-meat sources of iron with a good source of vitamin C increases the body's ability to absorb that iron.)
Dried fruits: I would occasionally eat some raisins or cranberries, but before surgery I went out and got prunes, dried apricots and figs, all good sources of iron.
I was told to cook in cast-iron cookware whenever possible. All my eggs were cooked in cast iron skillets. And before my surgery I made a huge batch of tomato-sauce and meatballs, in the cast iron, of course, and froze individual portions for quick microwaveable post-surgery meals. I also made some minestrone thick with dried beans, unpeeled potatoes, lots of tomatoes, peppers, spinach -- all iron-rich, or iron-boosting -- along with onions, garlic, and basil. I browned the onions, garlic, etc. in the cast iron skillet. I used the skillet, too, when I made kidney bean chili -- some with ground beef, some vegetarian. I made fruit compote out of a mix of prunes, apricots, dried peaches and pears. I cooked up a big batch of oatmeal. I divided each of these into individual and 2 or 4 serving containers, and froze them.
* I had a hard time finding liver in local markets, but lucked out when a smaller independent market occasionally carried calf's liver. I'd never had calf's liver before, and it was divine. Compared to beef liver, that is. Of course, I still ate it with loads and loads and loads of onions and garlic mashed potatoes, but even so I looked forward the leftovers. I had better luck finding chicken livers, and chopped liver at Jewish delis.
**They might be hard to find in Middle America, but Japanese restaurants do a pretty good job of grilling mackerel, or serving it as sushi so it doesn't smell or taste too fishy.
This may be TMI, but maybe you'll find it useful.