Walking for weightloss?

I only run when being chased, but I will walk for activity/exercise.  My co-workers walk during their 15 min breaks, but only go round a city block twice...so I kinda sked, "you walk that slow?"  Well the other day I overheard one co-worker saying that her doctor told her that walking was beneficial and all, but will do nothing for weight loss.  

So does anyone know if this is correct, or is it just because she is walking slow and not far enough?  (I can average 3.71 miles in under and hour)

Exercise alone does not lead to weight loss.  To lose weight you need a calorie deficit.  Exercise does however burn calories.  The harder you workout the more calories you burn.  This makes it easier to create a calories deficit and lose weight.

Also, keep in mind that walking faster doesn't necessarily burn more calories.

See this (scroll down to "Calories burned per mile by walking"

Notice how walking 2 MPH burns the same calories as 4 MPH?

Of course walking helps to burn calories and affect your weight... it just doesn't give you license to eat a thickshake because you walked a mile. If it didn't do anything beneficial to my weight, I'd like to know just how I've lost 43 pounds. :P In fact, at one stage in my life I dropped at least 20 pounds without going on a 'diet' at all - I was just walking a LOT to get to where I needed to go, and eating whatever I felt like... I didn't even realise that it was shrinking me!

Also, it's the length of time you spend walking that has more effect than how fast you go.

What i have found that your food intake as to be lower in order to burn 1 calorie, so if you are eating 2000 a day calorie then you will have to shaffe off 500 and each week add 5 or 10 minutes more to your work out. Also if you use 2-5 pound wrist and ankle weight's as your walking with them you will gain muscle mass and loose fat.

If you are waking in addition to eating right you will lose weight.  It worked for me.  I could barely make it around a block when I was fat and lazy but after the pounds went down and my walks got longer I found walking 5 miles a day a "walk in the park" and I would walk quickly to get my heart rate going. 

So the dr was right to a point but you do have to watch what you eat too.