The altitude correlation would seem to suggest drinking water in particular as a culprit, and suggests a simple and straightforward study that would settle the question once and for all: randomize a group of households to either receive reverse osmosis filters on their taps, or not, then track whether the people in those households become obese.
I checked whether this study has been performed, and as far as I can tell, it hasn’t. There have been studies that randomly installed reverse osmosis filters, but they were checking for something else and didn’t track peoples’ weight.
Another effect of altitude is the atmosphere, and there is evidence that the active ingredient in altitude decreasing weight is the thin atmosphere. For example, “One study on rats found that they ate 58% less one day after being transported to Pike’s Peak, and were still eating 16% less per day two weeks afterwards.” The immediate effect strongly suggests that it’s not caused by anything in the water source.
See page six of the paper for the authors dealing with this point. It’s certainly a potential explanation, but the map of obesity in the US does seem to suggest that being, say, at the mouth of the Mississippi basin is much worse than being on the west coast, despite them both being at sea level.
The mouth of the Mississippi basin is much poorer than the West Coast, and has a lot fewer Asians (who are exceptionally thin). I’d guess those things probably play a role.
That’s a map of highest elevation by county. I don’t think most people in LA County (third from bottom on the California coast) live above 6800 feet, because most people don’t live on mountains even if one exists in their county.
The map of average elevation by county looks similar, but you are right that this matters very little because people are disproportionally likely to live in low elevations.
Reverse osmosis filters will already be more common in some places that have harder water (and decided that softening it at the municipal level wouldn’t be cost-effective). If there was fine grained data available about water hardness and obesity levels, that might provide at least a little signal.
The altitude correlation would seem to suggest drinking water in particular as a culprit, and suggests a simple and straightforward study that would settle the question once and for all: randomize a group of households to either receive reverse osmosis filters on their taps, or not, then track whether the people in those households become obese.
I checked whether this study has been performed, and as far as I can tell, it hasn’t. There have been studies that randomly installed reverse osmosis filters, but they were checking for something else and didn’t track peoples’ weight.
Another effect of altitude is the atmosphere, and there is evidence that the active ingredient in altitude decreasing weight is the thin atmosphere. For example, “One study on rats found that they ate 58% less one day after being transported to Pike’s Peak, and were still eating 16% less per day two weeks afterwards.” The immediate effect strongly suggests that it’s not caused by anything in the water source.
See page six of the paper for the authors dealing with this point. It’s certainly a potential explanation, but the map of obesity in the US does seem to suggest that being, say, at the mouth of the Mississippi basin is much worse than being on the west coast, despite them both being at sea level.
The mouth of the Mississippi basin is much poorer than the West Coast, and has a lot fewer Asians (who are exceptionally thin). I’d guess those things probably play a role.
Educational attainment is strongly correlated with obesity rate across US states:
I used this obesity dataset from the CDC and this educational attainment dataset from the USDA.
Also, the mouth of the Mississippi basin does seem to be at a lower elevation than the West Coast:
That’s a map of highest elevation by county. I don’t think most people in LA County (third from bottom on the California coast) live above 6800 feet, because most people don’t live on mountains even if one exists in their county.
Oops, sorry.
The map of average elevation by county looks similar, but you are right that this matters very little because people are disproportionally likely to live in low elevations.
Reverse osmosis filters will already be more common in some places that have harder water (and decided that softening it at the municipal level wouldn’t be cost-effective). If there was fine grained data available about water hardness and obesity levels, that might provide at least a little signal.