The article notes a fact that so far hasn't come up in the discussion here: "For the first time in human history, overweight people outnumber the underfed, and obesity is widespread in wealthy and poor nations alike. The diseases that obesity makes more likely — diabetes, heart ailments, strokes, kidney failure — are rising fast across the world, and the World Health Organisation predicts that they will be the leading causes of death in all countries, even the poorest, within a couple of years." This is a good corrective to many theories about obesity, because cross-national comparisons will show that people can become obese on a variety of diets, and not all countries that have rising rates of obesity have the mix of foodstuffs as the United States.

I saw the submission and the first few comments before I cooked a home-cooked meal for my sons. (My wife is coming home from a soccer tournament trip with our daughter, so it is definitely my turn to cook this evening.) A book recommended in an earlier thread by a Hacker News participant, The Diet Fix: Why Diets Fail and How to Make Yours Work,[1] intrigued me enough when it was recommended here that I checked it out of my public library and read it cover to cover. The book is sensible and based on both scientific research and the author's own experience as someone who likes to eat a lot. The advice in the book boils down in large part to 1) do your own cooking, 2) know that your diet will fail every time you eat out, and 3) keep a food diary if you really want to be aware of what you eat. I do number 1 almost all the time. By the official designations on the United States federal government body-mass index website,[2] my current body mass index classifies as "overweight," but that is the optimal weight range for a middle-aged adult, epidemiologically, for longer lifespan. But correlations found in observational studies do not prove causation, and I might not be any worse off if I lost a bit of weight to come down to the "normal" weight range I was in during most of early adulthood. Until I was in my late twenties (that is, until after I got married), was thin--no, make that gaunt--because I did all my own cooking and I tried to spend as little as possible on food. I wonder how much my experience is different from that of other people I see commenting here on Hacker News because of age--I am a generation older than most participants here--and how much is different because of birth cohort--just about everyone I knew when I was growing up was slim.

All around the developed world, Life expectancy at age 40, at age 60, and at even higher ages is still rising.[4] But obesity (overweight that is more excessive than just being "overweight") is still increasing in all those countries, and indeed in nearly all countries of the world. Animal experimental models are pretty convincing about obsesity-as-such causing many kinds of illness and early mortality, and it will be an interesting question to see if obesity trends outrun the other trends that are improving healthy lifespan for most people in most places at all ages.

The article reminds us of the astonishing fact that this trend even cuts across species, as long as the species are in the care of current human beings: "Consider, for example, this troublesome fact, reported in 2010 by the biostatistician David B Allison and his co-authors at the University of Alabama in Birmingham: over the past 20 years or more, as the American people were getting fatter, so were America’s marmosets. As were laboratory macaques, chimpanzees, vervet monkeys and mice, as well as domestic dogs, domestic cats, and domestic and feral rats from both rural and urban areas. In fact, the researchers examined records on those eight species and found that average weight for every one had increased. The marmosets gained an average of nine per cent per decade. Lab mice gained about 11 per cent per decade. Chimps, for some reason, are doing especially badly: their average body weight had risen 35 per cent per decade. Allison, who had been hearing about an unexplained rise in the average weight of lab animals, was nonetheless surprised by the consistency across so many species. 'Virtually in every population of animals we looked at, that met our criteria, there was the same upward trend,' he told me." Exhorting lab animals to exercise more is of course not likely to help them much.

After the author reviews a number of hypotheses about obesity and possible causes for obesity rates rising, most of which we have discussed before here on HN, the summary paragraph makes an important point: "No one has claimed, or should claim, that any of these 'roads less taken' is the one true cause of obesity, to drive out the false idol of individual choice. Neither should we imagine that the existence of alternative theories means that governments can stop trying to forestall a major public-health menace. These theories are important for a different reason. Their very existence — the fact that they are plausible, with some supporting evidence and suggestions for further research — gives the lie to the notion that obesity is a closed question, on which science has pronounced its final word. It might be that every one of the 'roads less travelled' contributes to global obesity; it might be that some do in some places and not in others. The openness of the issue makes it clear that obesity isn't a simple school physics experiment." In other words, we still have to do a lot of research, and as I noted as I began my comment, maybe different countries have different obsesity problems with different causes.

[1] http://www.amazon.com/The-Diet-Fix-Diets-Yours/dp/0804137579

[2] http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmic...

[3] http://www.sciencebasedmedicine.org/the-obesity-paradox/

[4] http://www.nature.com/scientificamerican/journal/v307/n3/box...