In a city of purportedly 17 million people, you'd assume that folks have got to eat. And with that many mouths to feed and a deluge of tourists that consistently rank Istanbul among the ten most visited cities on Earth, you've got to believe that there are a ton of places to grab some food. Many travelers, unless they are conducting a food tour, will invariably seek their meals in proximity to the attractions, meaning that districts like Sultanahmet, Beyoglu, and Fatih are going to be crawling with restaurants and cafes. Not to say that such places lack authenticity, per se, but if you want to eat quality Turkish cuisine and/or spend time where only the locals go, then you'll need to make a genuine effort to get a bit further off-the-beaten-path.
We wouldn't set you up like that and then leave you hanging. Don't worry, we've got your cuisine option covered. If you're staying on the European side of the Bosphorus, there are still plenty of ways to meet the aforementioned criteria without catching a dolmus to a mountain-side cottage to eat Mercimek çorbası (lentil soup) with a goat herder (although if you have the chance, we urge you to take it). There are a number of neighborhoods that appeal to middle-class sensibilities with a great range of cafes and other unpretentious eateries. Akarsu Caddesi in Cîhangir has a good number of options near enough to some of the more touristy areas and is especially convenient if you're staying in on of the less expensive accommodations in the neighborhood. Further up the Bosphorus in the neighborhood of Beşiktaş is a great selection of cafes and breakfast places, as well as a fish market on Beşiktaş Square. The Dolmabahçe Palace or Ihlamurdere Caddesi are fine starting points.
If you're looking to stick with views of the river, then hang out in Ortaköy. The stuffed baked potatoes (kumpir) have a city-wide reputation and can't be missed if you're trying to pull an Anthony Bourdain. Stroll around just west of the bridge and you'll be overwhelmed by your choices. Lastly, if you want to get off the tourist track for a moment, it couldn't hurt to head south of the old city to the marina in Ataköy. There are some great cheap eats in the Ataköy Galeria, as well as along Fişekhane Cadessi, which runs parallel to the Sea of Marmara.
If you cross to the Asian side of Istanbul, you may be surprised that there are still plenty of places for a traveler to go, although the chances that shopkeepers and wait staff will understand your English are little to none. Don't worry, you can depend on body language to convey your love of doner. The popular Kadiköy district is distinguished by its abundance of Turkish grub south of Osman Aga Mosque between the parallel-running Moda Caddesi and General Asım Gündüz Caddesi. The sub-neighborhood of Caddebostan is a great place to start your cuisine journey; just stay along main thoroughfare Bağdat Caddesi and you'll encounter food to suit your style in no time. Then again, following Acıbadem Cadessi north through upper Kadiköy to neighborhoods like Koşuyolu will allow you to enjoy more affordable cafes and restaurants that won't force you to sacrifice yourself to unsanitary conditions.
This is merely a template. If we were to truly delve into Istanbul's hugely varying cuisine and the many corners of the city in which it may be found, then we'd have to release this summary to you like a serial novel. C'mon, no one wants 37 issues of Turkish cuisine. If you do, by all means let us know and we'll put a rain check on our next mountain climb and put our stomachs to the test.