I started at 315 lbs in June 2015 - over the last 2+ years I have lost 135 lbs (down to 180) - I did not diet - I changed the way I eat to clean foods - out went processed foods, white flour, white sugar - meals consisted of a protein (chicken, fish, pork), a vegetable and a potato (normally sweet potatoes) - I measured my food and counted calories everyday in MyFitnessPal - limited to 1850 at first - 1850 calories worth of zucchini or broccoli is quite filling actually vs lower quality processed options - I lost approx 2 lbs per week reaching 180 after about 16 months.

I started running in January 2016 (once I had lost 50 lbs) with a couch-to-5k plan - it was not easy with no athletic background of any kind - I have since completed a dozen 5k's and 10K's, a small handful of half marathon and I just completed my first marathon 3 weeks ago... I added biking about 15 months ago as a cross training alternative to running...

I still eat that way to this day - but I have added back in whole wheat breads and pastas. My weight fluctuates within 180-190 depending on how much I run during the week (it actually crept back over 190 during marathon training).

For me, the diet was the main part - counting calories kept me on track, and there are more than enough "clean" food options to keep me more than satisfied. The exercise definitely helps and should be a part of a healthy lifestyle - I look at running as allowing me to eat more calories as I burn them running...

I hope that helps...