I don't have a link, as it seemed self evident to me, but epidemiologists studied over quite some time a group of very hardcore Amisch in Southern Ontario. I think these people came from Germany, Switzerland and Alsace in the 19th century. They have strongly resisted modernizing their life. No tractors or other powered farm machinery, no labor saving devices for the women who are all homemakers. I don't know about refrigeration. Anyway, all the adults were given pedometers. The men averaged a bit over 18,000 steps daily, and the women somewhere just above 15,000. This is a very high caloric output, if they were not doing anything else other than walking around. But I spent my childhood summers on a non-mechanized farm, and walking around is only a part of what they do. It would not surprise me if the average male caloric output was ~1000 kc/day or more. As one might expect, there were very few overweight people of either sex, and no obese people. Their diet was described as "hearty".
1000kc/day is small beans for a swimmer in training, but a very large amount for people from young to well into middle age, going about their daily lives. I also have seen that if you do enough hard work, you are not going to be fat, no matter how much or what you eat. I lived in logging country before the spotted owl made logging a sometime thing. These guys looked like those old pictures you see of loggers with a big two man saw standing by a giant cedar or redwood or Douglas fir. They look like they have the body fat of Michal Jordan in his prime. They only gained weight when they were injured, or lost a step and got moved up to operating a crane or some much lower ouput job.
But try to tell some modern person that he will never get fat if he only commits to exercising enough to burn 1000 kc/day. Essentially impossible. Modern men and women of necessity spend most of their time sitting on their often ample butts.
In a recent blog post Stephan Guyenet adressed the exercise question, specifically the assertion that if you exercise more, you just eat more. He found that this is indeed true, for people with low bady fat. As he put it, the body does not like to let its fat stores get too low. However, he also found that people who had excess fat, although they did in fact eat more after exercising, they did not eat enough to completely replace what they burned. I don't know how good the evidence is, as I was primed to accept this finding since it corresponds with my own experience and my observations.
Ha