Patterns of Regional Cerebral Blood Flow as a Function of Obesity in Adults
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Part of me wonders about the directionality of causation here (If we assumed one existed). One could argue the hippocampus, which from my recollection is involved in inhibiting impulsive behavior, has a clear path to being a causative agent for obesity. Distinguishing between the two narratives of “Being overweight inhibits brain function” versus “Differences in part of brain controlling impulses leads to weight differences” is important to resolving it, as it is easier to imagine treatment regimens to combat weight more than brain blood flow.
It is also completely possible these two variables do not affect each other, but are correlated. That’s useful still, because it means we may be able to use body weight increases as an inferred marker for the brain changes.
It would be incredibly interesting if the story of Alzheimer’s transformed more into “Same factor may be causing both America’s obesity increases as well as Alzheimer’s cases”
Edit: Updated this a few times while reading the original paper
I don’t think the science (As in the raw data and charts) is necessarily bad, but the title of the linked article (Which is not the title of the original article) is needlessly imprecise (Or precise in the wrong ways, I suppose).
The authors claim (but don't show their work) that adjusting for these factors did not change the statistical significance of the relationship, but it does still mean this isn't exactly a representative sample of the population.
Very interesting that underweight people generally have more blood flow than "normal" weight people, though if you dive into the supplementary data that doesn't hold for every region of the brain studied (and the general trend seems to hold in all regions studied).
Edit: It is fairly easy to be < 25% body fat with normal musculature that accompanies normal weight lifting and cardio routines 4 times a week. That will get you to a BMI +30 at 5"10 +
Armed with that, I'll choose a p value myself, as to whether it's rare. Anecdotally, I agree, but I can't be sure that I am in contact with a represeentative sample.
Edit:I counter with anyone who lifts and play sports and is 5" 10'+ will hit < 25% body fat and a bmi +30. You only need to be 225 pounds and at 6" 1' to be bmi +30 at 5" 10' that's only 210. I saw that fairly regularly (or at least I did precovid) at the gym.
Yeah, I saw (pre-covid) it all the time at the gym, at amateur sports leagues, and at health food stores. It's also worth noting that my zipcode also has a significantly lower obesity rate than the national average. If I were to go to an Alabama Walmart the fit & muscular people people would be much more uncommon.
That's a BMI of 30.8 which put him on the bottom of the "obese" range. (Obese starts at 30). Obviously he's not obese.
But most people who claim that they "BMI Doesn't apply to me" even though their BMI is over 30 don't look like The Rock. And he _just_ hits the obese range!
If you're not an elite professional bodybuilder or weightlifter (i.e., you don't look like The Rock) BMI is probably a very good rule-of-thumb.
A quick google search has him at ~10% body fat and 6’3” 236 lbs. That means his lean body mass is 212 lbs. So he could gain ~21 lbs and still be squarely in the average range of body fat (20%). Tack on 8-10 lbs more for the high end of average (24%).
With the 20% number, his weight would be 257 —- that’s squarely in the BMI obese category for someone who is 6’3”.
The BMI numbers are just not useful for folks with a relatively high amount of lean body mass for their height. One does not need to be a body builder or gym rat to meet this criterion. A small amount of body-weight exercises plus cardio is enough for people who build muscle easily (it’s not that rare).
As others have said, BMI can be useful for measuring trends in populations, but some people get carried away when using it on individuals.
I'm a "gym rat" (I'm the co-owner of a gym). Lift weights every day. I look athletic. I'm 5'10" 170#. That's a BMI of 24. Not even in the "overweight" range.
Most people who say "BMI is meaningless/unfair/outdated" aren't in the group of people who outliers.
It is a very good quick check, especially for considering the characteristics of a population when looking for correlations (like obesity vs cognitive ability, or obesity vs Type II diabetes). Doctors tend to record height and weight of patients with reasonable accuracy. Even doing other measurements like hip/waist ratio are a bit subjective (where, exactly is the waist. Where are the hips--especially on an obese subject. How "tight" are you holding the tape measure?) BMI eliminates those subjective elements.
I’m 5’11” and 176#... of lean body mass per the last time I was in a dunk tank pre-covid. I am a desk jockey, I haven’t lifted a weight in over two decades, although I do cardio and body-weight exercises (push ups, pull ups, burpees, etc.). Needless to say, I’m an outlier while not being a gym rat, body builder, or construction worker. I don’t think people like me are rare enough such that concerns over BMI on an individual basis can or should be hand waved off.
Every time I see a new doctor, they tell me I’m obese, I might be diabetic (my numbers are very normal), and how we might want to talk about that.
I show them my dunk tank numbers, my myfitnesspal records of my diet, and my blood work, and they always just say “carry on”. I share this story to show that even medical professionals rely on BMI to an irresponsible level sometimes.
I’m able to come prepared to the doctors because I understand the limits of BMI. I have several friends of similar build who have freaked out and sometimes made very stupid lifestyle changes (vastly undereating given their activity level) due to sloppy advice from doctors based on BMI.
I’ve seen this cut the other way, too, with folks who have perfect looking BMIs but low lean body mass and are very unhealthy.
I stand by my stance that BMI is good for measuring populations of people, but it’s a very crude tool on an individual basis. I hope my anecdote shows how this can happen even for a relatively normal person.
I assume like with most things athletic individuals would have less risk anyway.
"When compared to white Europeans of the same BMI, Asians have 3 to 5 percent higher total body fat. South Asians, in particular, have especially high levels of body fat and are more prone to developing abdominal obesity, which may account for their very high risk of type 2 diabetes and cardiovascular disease. In contrast, some studies have found that blacks have lower body fat and higher lean muscle mass than whites at the same BMI, and therefore, at the same BMI, may be at lower risk of obesity-related diseases."
https://www.hsph.harvard.edu/obesity-prevention-source/ethni...
‘Regular exercise linked to higher blood flow in brain’ seems a more appropriate, not dramatized headline. Thank you Captain Obvious.
I would also think, based on some people with eating disorders I've observed where the weight decreased, that a very low body weight also might have an alarming impact on brain function - not sure how surprising it would be and if really a cause and not a correlation. Probably just a correlation.
Most people equate weight=high BMI, so the title is probably accurate for a casual audience but it's important to note the study is actually looking at BMI.
Being fat is an enormous risk factor for dying of Covid, but instead of a giant “Get Out and Jog” campaign we are just supposed to hunker down inside and pray for a vaccine.
Being fat is a sign of generally poor health. It hurts your immune system. It reduces your quality of life. It has ripple effects to the rest of your body.
The fat positivity movement is one of the worst movements ever to exist. There is nothing positive about being fat. It is only negative.
It would let people feel like they’re doing something to fight the disease. It would bring us positivity instead of negativity, and the health improvements would pay dividends for years.
Oh also a massive volunteer effort for healthy people to deliver food and medicine to the elderly and vulnerable.
My mother and his husband received several offers from young couples in the block to go buying groceries or make any other errands and leave them outside the door.
The vitamin D and C were sent by me through Amazon :)
https://news.ycombinator.com/item?id=23940405
Ochen' vyros v tselom mire
COVID virus - tri... chetyre...
Edit: people can do something to fight the disease: keep distance from people they don't already live with (and wash their hands). They can do this, but in some places they don't.
(I worry about the people in my country who won't: we're already back up to about 30/million new cases per day, after having been down to single digit total new cases.)
https://www.lemonde.fr/les-decodeurs/article/2020/03/27/coro...
Edit2: for what it's worth, the private insurers here sponsor fitness trails all over the country, because they have an economic incentive to pay out fewer, lower, claims.
https://en.wikipedia.org/wiki/Fitness_trail
(and grocery and pharmacy delivery was already a normal thing, before.)
I get that recognizing humanity and compassion for everyone is important.
But what more evidence do we need of the outcomes wrt covid where Japan has a 4% obesity rate vs US 40%. We’re talking an order of magnitude disparity.
Maybe high blood pressure is the body trying to compensate for reduced blood flow?
If I get a spike, it can take a week to be back to normal brain function.
It puts a lot of pressure on the veins, taking them close to bursting. Body needs time to heal.
One insidious part is that exercise makes it worse. So if you exercise, pressure spikes, you need a week or two to recover.
I spent years trying to push through exhaustion, but everytime I worked out I would need weeks to recover. So I made little progress.
Proper diagnosis and medication suddenly enabled me to exercise daily. Massive life changer.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651104/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737453/
etc.
However, this is a topic that we are not allowed to discuss here.
A layman would also look at a country like say, America, where obesity has been on the rise for decades, and the population seems to get increasingly uneducated and insular, and deduce this to be true.
Is it scientifically rigorous? No, but sometimes there isn’t enough time for rigor and you’re better of making an educated guess than having no conclusion at all.