Many runs can change your life

I have been a runner since my primary school days, those day we used to steal fruits from trees like Gooseberry (Amla) or guava, berries, mangoes, Chiku (sapota) etc from the trees nearby and the Gardner of the orchard then used to give us a good run for our life. Then we used to run after the kites cut from the kite race and was floating in the air and whoever caught it first used to get it, we also ran school races regularly and while playing cricket daily running was our passion.

Then began running for my high school’s team event in field and track teams as a freshman. Before, I had valued exercise and academics, but not enough to do it every day. Once I started running consistently (6 days a week), I noticed physical improvement (of course) along with mental improvement. Running every day will obviously make your heart and muscles significantly stronger, but it will also make your brain stronger. Let's say you go for a 5 km run.

When you reach km 4 or so, you feel like you want to give up. But you don't; you keep pushing all the way to the finish. Consistently pushing yourself when running transitions to other tasks. In other words, it makes other tasks feel easier. When I'm assigned a ton of homework, my runner’s mentality kicks in. I power through the assignment, even when I experience discomfort (boredom). It's hard to explain, but basically, running every day helps you persevere in life. Whenever you are given a challenge, you push through as if you are running. 

I forgot to mention that running improves your diet and sleep. When I started running consistently, my body naturally craved healthy food to replenish itself. You don't finish an 8 mile run and say: “I want a coke”. You want water. I’ve run so much that it feels wrong to drink anything besides water or milk. Additionally, running makes you very tired (obviously). So you naturally get a lot of solid sleep, something essential for a healthy lifestyle. And since you get plenty of sleep, you are energized for the next day, so you don't need to be reliant on caffeine. It's a large cycle: when you consistently exercise, you naturally eat and sleep better. In order to truly improve your health you need to start running, the other factors will follow.

I run 6 days a week and occasionally 2 times a day even keeping Sunday as day of recovery. My knees are not shot. My body is not wreaked (nor is it wrecked). My motivation is not diminished, it is strengthened. Basically blanket statements are just not helpful. As a runner, I would ask you a number of questions about your fitness goals and motivations. Then you can decide if your personal fitness level, motivation, and physical ability would benefit from running daily. IF….and that’s a big IF….Running daily is a good fit for you, here are some potential benefits:

The mental toughness of enduring the grind. Even embracing the grind. That will make you a tough racer, and probably a stronger person in other aspects of your life. Running daily gives your body a regular, predictable stimulation. The constant calorie burning, consistent flow of hormones and other bodily functions will add a consistency to your physical well being and mental well being. Better racing performance.

I don’t know any really competitive runners who train less than 7 days a week. There are occasional exceptions to the rule but generally, top high school,collegiate, professional, masters or just really competitive distance runners train every day. The total volume of miles is a key factor in performance improvement so if your volume of miles goes up and you sustain it for a long period of time, your cardio performance will improve. And also, I’m tired of the body shaming about a runner’s physique.

Running streaks (where you run more than 1 mile a day) can go on for over several years. I recently did it for a month with just running 1.6k on my rest days. I found it rather helpful and prevented some of the muscle ache that you get after long runs. If you run too far every day then you'll pretty much guarantee yourself a knee replacement by the time you are 60 but I have crossed 62 now but still don't have any issues. Also you’ll find your free time will have shortened considerably (and no one really wants to be that person who can only talk about one thing).

As the other answers have stated the fitness gains can mostly be achieved with running 3–4 times a week. So why bother? Well I guess the pros are that you generate a really nice daily habit of running, and even when travelling you take your trainers with you to explore wherever you are. The time spent running is often a good way to destress and so you’ll feel even more relaxed than if you only did it 2–3 times a week. Finally if you are running sufficient amounts you can basically eat loads of stuff - especially chocolate milk, as you are nearly always perpetually hungry (at the peak of my marathon training I was burning 3500+ calories a day). Serious athletes with far more talent and motivation will eat way more. Cheers!