I would agree.
A generation or two isn't enough time for genetics to change much.
I'm unsure what to think about the whole gut bacteria thing. It seems odd to me that it could have that much of an effect, that the effects only started recently, and mostly in industrialized countries.
I put a pin in 'the whole gut bacteria thing' at this point - it's basically at what i'd call the 'plausible hypothesis' stage. Like so much mouse research it will probably have no bearing on humans (*cough* calorie restriction *cough*), but who knows.
We, as a society, tend to have a more sedentary lifestyle than in the past.
It depends on how far in the past we compare, and how we define sedentary lifestyle. Studies have been done to measure activity levels that contribute to calorie burn going back a few generations, and while there's imperfect methodology (no pedometers 100 years ago), we seem to be almost as active as before. Kids today are probably even more active than ever before. In any case, there's no evidence that the quantity of decline in activity is equal to the calories accumulated in people's obesity. It doesn't add up. But the food intake increase can account for probably 80% of it. So it's the best explanation.
However, this is because people have more sport activities - obviously, our everyday jobs are less active.
Current estimates are that the increase in population %age with obesity is about 20% from decline in activity, 80% from increase in caloric intake. Addressing eating is the biggest bang for the buck.
I fully agree about the commercial interests. We have essentially unlimited access to a wide variety of inexpensive, delicious food, much of which is designed to limit the satiety response and keep us eating. Plus there's all the marketing that goes into food.
Unfortunately, I think marketing is the big one.
Like the Cylons: they have a plan.
Obesity is not a side effect of marketing: getting people to eat more food is the entire purpose of their marketing. They spend literally billions of dollars a year making it happen, and they're not above lobbying the government and funding expensive campaigns based on deception and half-truths. Facts and willpower don't stand a chance.
Here's why it's complicated: I just read a medium quality 2012 study of the impact of 'after school sports programs' - ([
Do youth sports prevent pediatric obesity? A systematic review and commentary.]) the results were what I predicted: participation in after school programs (including sports) is positively correlated with obesity and junk food consumption and total calorie consumption. This is because the junk food marketers have been concentrating there for quite some time (eg: [
Amateur Hockey Canada]) - it's a 'target rich environment' (kids don't have willpower to resist advertising - why should they?). So, the hockey kid is more likely to be a junkfood junkie with obesity than the kid who opts out and plays Nintendo in his basement.
This study is not a one-off - it is entirely consistent with probably another hundred examining the situation: physical activity levels are not very strongly related to whether a person has obesity (see below), and secondly, children's sports is a critically important advertising environment for junk food sellers, establishing hard-to-break habits and beliefs for life.
Regarding exercise and obesity: Here's an example of a higher quality study about this: [
Maintaining a High Physical Activity Level Over 20 Years and Weight Gain]. Exercising intensely an hour a day six days a week for 20 years appears to result in 4.5 fewer ounces of weight gain. Not weight
loss, but just
slightly less weight gain.
