Is it easier to lose weight through diet or exercise?  

Most people can lose weight just by reducing their calorie intake 500 calories a day. They can eat the same things they are seeing and gain results from it. Even if you eat nothing but fast food, that reduction will help you see weight loss. This doesn't work for everyone though, some people have to cut out sugar and other things in order to see true results.

I think overall, the easiest approach is doing both. Reduce your daily calories a bit and just be more active. 

Diet is probably easier but if someone struggles with food addictions or stress eating, it likely won't be. It comes down to your age and free time. For me, it is easier to eat less than it is to stick to working out.

You can lose weight from walking. My mother did this. She got a dog and walked him every evening after dinner for 30 to 40 minutes a day. She didn't change her diet at all. I think the key for this to work is that you have to already not be eating in excess and also not eat extra once you start moving more.

I have lost weight not changing anything before, happened 3 times. I didn't focus on weight loss at all. What I was doing at those times was being more busy so I was eating less and just moving more. I didn't exercise or restrict my diet. I just became more busy!

I don't think you can exercise away a bad idea. That being said, I think diet is more important when it comes to losing weight and I think it is easier to stick with vs exercising but doing some form of "extra movement" is good for your health anyways. Parking further away from places you need to shop at, taking the stairs, little things like this add up.

Diet is easier. It takes a 40 minute walk at a moderate pace to burn off 200 or so calories. Most people workout 30 min to and hour. So consider it to be something like 250 calories burned on average. If you change nothing in your diet and are already overeating, you will not see any changes.