Way to make this decision ConeArrow27. I could go on and on about this subject, so I try to keep it short.
Like stated already, what you eat plays a bigger role in health. There is a huge difference in being healthy and being fit. To be healthy, and stay healthy,requires a lifestyle change. The biggest thing is reducing your processed/refined foods, and don't take in empty calories. When you eat you want to eat nutrient dense calories/food. Those are best found in whole foods like fruits and vegetables(plants). Don't focus on calories, and especially don't cut calories. Just make sure you are eating nutrient dense calories that are high carbohydrate(not sugar carbs) and fiber, and balanced in protein and fat. Don't add fats like oils and dairy to your diet. Cutting dairy out of your life is another thing that will help you lose weight pretty quick. A big factor in weight loss for the majority of people is hormones(dairy also packs a lot of hormones that are foreign to the human body) and stress. Stress, good or bad, causes the body to release hormones which can cause fat storage and fluid retention. That said, take it easy with the physical activity. Progress slowly to reduce the stress on your body and reduce the chances of raising stress hormones too much, and physical injury. Something most people overlook when becoming physical/exercising, is getting a physical/check-up by a doctor. If you have existing medical issues or possibly something you don't know about yet, like high blood pressure, then over doing it could be detrimental.
Something I highly recommend is getting fitted for the proper running shoes at an actually running store that can evaluate you and the way you run, and fit you to a shoe the works best for you. I see people all the time that over pronate(foot excessively rolls inward) and are wearing a shoe made for someone that has high arches and or supinates. Knee pain can indicate several things. Everything from the wrong shoes or worn out shoes, to an injured knee or skeletal misalignment. If it were me I would get to a chiropractor before buying new running shoes though, as a chiropractor can assist in correcting an issue that a running store may try to fix with a shoe or insoles.
Biking is one of the best exercises for overall health, fitness, and is pretty much a no impact exercise.
I'm majority(99.9%)vegan/plant based, and having been getting to this point for about a year now. I have lost about 10lbs(now 145) in the past year and don't workout at all. I was about 165 in 2010 when I got out the Navy and was very active. I ran, cycled, rock climbed, lifted weights, etc. Now on a planted based lifestyle and not active more than working/detailing and walking my dog everyday, with the occasional jog with him(less than a mile), I weigh less than I did when I graduated high school in '99 and was running track(less than 5 minutes miles and just over 2 minute average half mile). But in high school I drank soda, ate junk food, fast food and meat. If that's not proof that what you eat matters more than your physical activity then I'm not sure what does. Not bragging, just telling my perspective/experience.
Alright, that went way longer than intended. Hope some of that helps.