[zdragnar]

There's an oversimplified assumption here that the plants will be less nutritious, and so people will eat more calories to make up for the deficit.

I suspect the presence of protein, fats and sugars influence the hormone production regulating appetite far more than these changes account for. I would expect the same health issues to be affecting other animal species in just as drastic a measure as humans if it were true, and also that global obesity happened at a more uniform pace rather than coinciding with the introduction of modern western eating habits and lifestyles.

[hxorr]

It's not just an assumption, there is research that shows this.

For example: https://www.scientificamerican.com/article/as-co2-levels-ris...

More specifically, yes, protein content decreases with rising CO2 levels. Maybe not enough to cause obesity on its own, but enough to be a compounding factor. Especially when your staple is, say, rice -- which is what the paper linked above looks at.

[zdragnar]

The assumption is not the variation in the nutrient counts, but in the link to obesity.

The rise in obesity has much stronger correlating factors than CO2 levels- diet and sedentary lifestyle being far stronger.

This is especially obvious when looking at the cited study:

> The new study evaluated 18 types of commonly grown rice to see how they would respond to elevated levels of carbon dioxide. In the experiments, the researchers increased ambient carbon dioxide levels to concentrations between 568 and 590 parts per million. Currently, atmospheric carbon dioxide concentrations hover around 410 ppm—but at the rate they’re currently rising, they could reach the high levels used in the study by the end of the century, if action isn’t taken to curb them.

The study examines the behavior at levels of C02 we don't currently have. The decline in nutrients has, thus far, been too small to have the impact on obesity we've already observed.

[frm88]

In the last sixty years, there has been an alarming decline in food quality and a decrease in a wide variety of nutritionally essential minerals and nutraceutical compounds in imperative fruits, vegetables, and food crops. The potential causes behind the decline in the nutritional quality of foods have been identified worldwide as chaotic mineral nutrient application, the preference for less nutritious cultivars/crops, the use of high-yielding varieties, and agronomic issues associated with a shift from natural farming to chemical farming. Likewise, the rise in atmospheric or synthetically elevated carbon dioxide could contribute to the extensive reductions in the nutritional quality of fruits, vegetables, and food crops.

The decline in nutrients isn't limited to rice and/or CO2 levels but spread across almost all varieties of fruit, vegetables and food crops with margins as high as 80% dilution and causes from chemical/genetical agriculture to rising CO2 levels.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10969708/

https://www.youtube.com/watch?v=ngjAqzam0fU

[red75prime]

Some varieties of rice are less (or positively) affected. Those varieties will be used more.