I agree with you about the refined carbohydrates but the underlying facts about the thermodynamics are also important, but in a slightly more subtle way. Peopl

I agree with you about the refined carbohydrates but the underlying facts about the thermodynamics are also important, but in a slightly more subtle way. People almost always underestimate just how incredibly - almost unbelievably - efficient the human body is. We're used to being impressed by cars that can do 60 mpg, but the human body can easily manage 300 mpg, even for an unfit hacker like me; fitter people will be slightly more efficient, maybe up to 400 mpg (http://health.howstuffworks.com/health-illness/wellness/physical-fitness/weight-loss/diet1.htm http://health.howstuffworks.com/health-illness/wellness/phys...). What this means is that you have to run an enormous distance to burn off even a tiny amount of food - about 1 mile for every 100 calories. So you can run a mile on one banana (http://www90.wolframalpha.com/input/?i=banana http://www90.wolframalpha.com/input/?i=banana), or 1.5 average cookies (http://www90.wolframalpha.com/input/?i=1.5+cookies http://www90.wolframalpha.com/input/?i=1.5+cookies), or just over one rasher of bacon. You can run a entire marathon (26.2 miles) on 2,600 calories - or one big mac and a packet of cookies. A scary number of people in the western world eat enough to run a marathon every single day and still have enough calories left over of keep themselves ticking over (~1500 calories) - without changing their diet at all. This wouldn't be physiologically supportable for wear and tear reasons, but calorie wise a lot of us could support it. These two facts in combination: the abundance of high quality, high calorie food in the developed world, and the incredible efficiency of the human body are a virtually guaranteed recipe for obesity, whatever other factors come into play. The fact that almost all of the easily available junk calories people consume come from highly refined carbohydrates (because these are so cheap to produce), massively compounds the problem. Obviously there isn't a 1 to 1 relationship between calories in and weight gain and everyone is slightly different and most food isn't just converted into glycogen and then to fat, etc, etc... but as far as I can see, most people will not reasonably be able to burn off the calories from an average western diet, no matter how hard they try - there just isn't enough time to run that far and hold down a job. Trying to do that much exercise, on top of trying to diet and do everything else is just too much mental strain. On the whole, I think people are better off just not eating the carbohydrate in the first place - cutting it off at source is much easier than trying to get rid of it later, and only requires you to do one thing, rather than two.