My own opinion: we are seeing what happens when we combine an increasingly sedentary lifestyle with eating mass produced, low quality foods. Fruits and vegetables are becoming decreasingly nutritious. Animals (even organic) are force fed poor diets to slaughter them a few days earlier, whose fats contain high concentrations of these poor diets. There are lots of examples of food quality going down.
I especially think the problem is related to a combination of excessive carb intake, and PUFAs (think vegetable / seed oils found in a huge portion and variety of foods). There is a growing body of research this is the case [1].
DYOR.
I do agree the author's have taken some leaps. Leaps have to be taken as there is imperfect data to support any theory on the obesity epidemic, but I agree that leaps should be better acknowledged.
I think authors list convincing arguments:
1) the diets on average not working for weight loss
2) experiments with overfeeding causing a little of easily revertible weight gain
3) lipostate theory with understood possible pathways
This is a very strong claim that is lacking a source. There are entire groups of people in history that were documented to be obese, especially in religion or sports.
They are citing overfeeding experiments.
That kind of stretch is not even necessary for the main point of the article, so I think it is just decreasing its value.
Also I cast doubt on those overeating experiments: wrestlers and powerlifters keep fat.
This is also a very strong claim that is lacking a source :)
If you have thing X that you think might be partially caused by A, B, C, D you need to rule out B, C, D, before you say that A causes X. Otherwise we're back to 5G causing covid because if you draw a map of cell towers, it lines up with a map of hard-hit covid areas.
For a concrete example, I'm reading a theoretical neuroscience paper on dimensionality. The authors found an interesting relationship, but they spend a lot of paper on showing that 3 or 4 different known things are not the cause of this interesting effect. They do this by measuring the extent to which the other known effects explain away the effect. When all that is done and a significant effect is still left, then they conclude that they've found something new and real.
Humans are wired/encultured to find narratives more interesting than facts. So the watershed thing is a well-written narrative that makes it convincing but does nothing to establish the truth of the matter.
While there are many many factors affecting obesity, I am still convinced that the most significant factor is that people are basically delusional about how much they actually need to eat and how much energy is actually in various foods. I could be wrong, but I've seen no rigorously done science that convinces me otherwise yet.
I remember what it was like in the '80s. People just ate a lot less at every meal -- our portions have become ridiculous. If you work with immigrants (e.g. Russians). Look at some trim people and see how much they bring for lunch. One small sandwich, an apple, maybe a small salad. That's it. Pretty much any store or restaurant-bought meal here is going to be much more calorific than that.
The whole "low-quality" foods thing strikes me as new-age marketing. There may be something there, but again I believe the overriding factor is that most people don't understand how little they need to eat when they're driving and sitting all day.
EDIT> Also, in the '80s it was basically a luxury to eat out. You weren't going to go to Starbucks and have a cake in a cup for $5
EDIT2> I've watched smart people struggle with weight-loss and overeating my whole life. The excuses and delusions would not be surprising coming from a heroin addict. When I was 210 pounds after being 190 in university, I looked fat to myself. When I was 230 pounds after being 245, I looked slim to myself. This tells me that I, and the other people I have observed cannot be objective about food and weight. So I am very skeptical of non-rigorous opinions or popular-press opinions on the matter. I over-eat when I feel sad about having eaten too much -- that's literally crazy, and I've observed this craziness in everyone else I know who is fat! Food is such a social thing that we have person after person enabling and affirming our own bad habits. Grandma hopefully would never offer you a hit of heroin if you told her you were trying to get sober, but she'll totally offer you a big piece of pie if you tell her you want to lose some weight. Other people around the table will tell you "It's okay -- just this one time," and if you strenuously object you're being rude. We are delusional about food.
EDIT3> In summary, we are extremely biased to find any reason other than we eat too much, and the quality of a lot of the writing and even science in this area is pretty low and compromised by financial motives.
Why do you think that people become delusional or have become increasingly delusional in the last 40 to 50 years?
I'm pretty convinced that things like adenovirus 36 infection, phthalate exposure (especially in utero and as a young child) are obesogenic. I do think you're right that people are probably eating larger portions than in the 80's and often eating more calories, but I wouldn't be surprised is a large part of the reason why was because of obesogenic compounds and diseases.
Another reason I find this easy to believe is research on body weight homeostasis is pretty convincing. The leptin system is pretty strong at getting (some) people to eat less after eating more than usual one day and getting them to eat more after eating less than usual. There is also convincing research on what researchers call the gravitostat which, independent of leptin, alters hunger through weight-dependent signals from osteocytes in the large bones of the body.
I don't disagree with this, but I think there must be another compounding factor. People never used to count calories, and yet in my own (150lb loss) experience it is necessary because my body wants to eat more than it needs to.
For example, taken from the first article:
> In the past, most people got slightly leaner as they got older.
How can you claim that with so few data. From the same data I would conclude that obese people die at young age...
I don't think we should exclude any possible cause but a global contaminant which is the only cause of obesity seems far fetched.
Simple logic would suggest that our food is the main culprit.
Personaly I would bet obesity is due to weakened gut microbiome (due to consumption of process foods), transmitted from mothers to their children. In other words, each generation consuming processed food gives birth to children more susceptible to obesity. It has actually been modeled with rats (cannot find the published link though).
Then, why does it happen in wild animals? They are not eating processed foods.
Even if the food is main culprit, it leads to the question of what is exactly wrong with the food?
p.s. we have enough data to understand overall historical trends and authors cite it:
All are fed with human produced food. Also as someone noted our food (raw food) is decreasingly nutritious when it comes to micronutrients and vitamins.
I am blaming sucrose being added to literally everything.
The altitude maps are interesting because it presents the hypothesis that less oxygen could be preventing the negative effects of some compound on metabolism.
Phthalates, Adenovirus 36, bisphenols, certain pesticides and fungicides--which ones should we be investing in getting rid of?
