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As part of the test, the large-eaters on an average day ate more than twice the number of calories (2,857) as the small eaters (1,262). But here’s the part you’ll hate. The large-eaters had a lower body mass, less body fat, and, at an average of 118 pounds, weighed less than the small-eaters, at 134 pounds.

And
http://www.ajcn.org/cgi/content/abstract/53/2/425

The bottom line?

Your calorie needs are different than your neighbor's. You and I each eating 2,000 calories a day won't make us each the same weight.

This is kind of why I wonder how people can put any faith in calculating their BMR. I know people who eat 3000+ calories/day and do nothing but sit on their ass and have <10% body fat. I also know people who work their asses off, eat a normal 2000-2500 cals/day, but have over 20% body fat.

It seems to me that it's based solely on genetics and everyone is different, which is why so many people stress "You gotta do what works for you, not what worked for 'him'."

"Eating like a bird" is definately not the way to go. We all know that here. Those women who are in that category probably have jacked up metabolisms.

I've seen a similiar study in which a group of people, with the same activity levels, were given an extra cheeseburger a day in addition to their normal calorie intake. They found that over the course of a month of two, some people barely gained any weight, like a lb or two, while other people gained 10 lbs +. The conclusion of the study. The people who didn't gain weight, fidgeted more. Not genetics, not different exercise levels, not metabolism.

I hate when people use genetics as an excuse. A majority of the people who claim that genetics are the factor in their being overweight are just using it as a crutch. Oh, my mom was, overweight, so was my dad, and my grandparents and whatever. Chances are, that's just because your parents ate like crap, you grandparents ate like crap, and lived an inactive lifestyle. The reason that you're overweight is because you've inherited those very same behavioral habits. Let's say you're one of those 10% of people from the above group that really do have genetic issues. Is that really an excuse to sit on your ass and cram potato chips in like there's no tommorow?

Of the people here, I'm sure that there's at least a handful of people that were once part of the above group. Now that they're eating clean, and exercising, are they not losing weight and making progress just like everyone else? Maybe not at the same rate as everyone else, maybe faster, maybe slower, but that's life. Point is, using genetics as an excuse to stay fat is lame.

Not sure if your post was flaming me for my last comment, but if it was, you totally misinterpereted my statement.

I'm not fat, never have been and the only people close to me who ever have been all lost 50+ pounds. I do not find genetics as an EXCUSE to NOT lose weight, but it certainly has its presence in weight loss. I disagree with some of what you said. Genetics DO effect people's path to weight loss. It does NOT make it impossible, by any means. It just makes it harder for some. More importantly, the key is, like I said earlier that "you must do what works for you". Everyone's body responds differently and therefore you can't just have the world follow one routine/diet; it won't work.

I think people give genetics too much credit without factoring culture and history, especially how cultural eating habits have not dramatically changed in comparison to cultural work habits. Yeah you can say that your grandparents are fat or your parents are fat; but that's just how you remember them.

Think about it the 'good, wholesome' foods that older generations are reknowned for eating result in 3-4000 calorie diets a day, usually in three big meals. Lots of eggs, bacon, breads for breakfast, and cold sandwiches (usually some kind of meat, my grandpa liked bacon drippings sandwiches) and don't forget the milk. And dinners were massive as well. This seems to me especially true of farmers, but it's also true of factory workers, and 'grunt' labor. They may have ate a lot but they were on their feet all day in tough manual labor. very very few people had ripped physiques, but they were in excellent shape. These cultural factors shaped the way we cook and approach food, but those approaches seem to change slower than the actual cultural changes. With the rise of sedentary suburbia alongside bluecollar jobs, we've seen the huge rise in obesity that is getting so much media attention today. I'd bet if you go back and look at the obesity numbers that today's trend started in earnest a little after world war II, computers have just exacerbated the problem.

Is cultural heritage the only reason? absolutely not. But neither are genetics, diet, bmr, or metabolism. All these things can be primary factors, but the body is such a complex instrument there are so many factors acting in simultaneous concert it is hard if not impossible to determine the single important factor that affects everyone the most.