I used to think that too. After all, it was so common sense.
I posted my story elsewhere but I'll summarize it here. In 2003, I lost over 100 pounds on a low carb diet in just over 7 months. I did this by walking first 5 miles a day and then eventually 10 miles a day. On weekends, I would take extended 10+ mile hikes in the woods. I was in fantastic shape and I attributed my weight loss to exercise more than my low carb diet.
So once I started bring carbs back into my diet, I found that I had to exercise harder to keep up. Eventually I started to put the pounds back on even as I exercised more. Now I kept the calories about the same, but was now having more pasta, rice and breads and less steak, eggs and cheese. I thought that was a more "balanced and healthy" diet as I could not believe eating mostly meat and high-fat foods was good for the long run.
Well last November, I realized that I had put all my pre-2003 weight back on and then some. I now have to lose 120 pounds. I've lost 36 pounds in just over 10 weeks. It's almost scary how fast the pounds are dropping off just by changing what I eat. Yes, I still exercise but I think that's just a small part of it. And with the snowstorm we got last week, I haven't been out for my daily walks at all. Yet I've dropped 3.5 pounds since Saturday.
Don’t lose weight TOO fast - that can be dangerous, also.