New research suggests obesity impacts brain response to nutrients for life

JustSomeEm

Interested in your thoughts here - a new study suggests a potential biological component to obesity.

News article: https://www.statnews.com/2023/06/12/obesity-brain-response-nutrients-study/

Actual study (I haven't looked for a free version, but the abstract is there...): https://www.nature.com/articles/s42255-023-00816-9

What say you?

neanderthin

Whether the difference in hormonal response lasts a lifetime is a bit iffy but the differences are there, hormonal signaling is for the vast majority impaired in the obese, nothing new there. It's a 12 week crossover design with 60 people.

threewins

This is not new information, I remember something about hormones and brain hunger regulation after major weight loss about 10 years ago. Anyway, The Biggest Loser participants have shown that regaining lost weight is very common.

However, if you eat more protein, can you cancel the effect? Maybe eat an apple before a meal? We don't know what effect those two behaviours will do to control the irreversible chemical changes. It doesn't bother me, for 2 reasons #1 the difference between my highest and goal weight is 'only' 32 kg and #2 if at goal weight I am ravishingly hungry, I'll increase my protein and apple intake and see how that goes.

threewins

This is not new information, I remember something about hormones and brain hunger regulation after major weight loss about 10 years ago. Anyway, The Biggest Loser participants have shown that regaining lost weight is very common.

However, if you eat more protein, can you cancel the effect? Maybe eat an apple before a meal? We don't know what effect those two behaviours will do to control the irreversible chemical changes. It doesn't bother me, for 2 reasons #1 the difference between my highest and goal weight is 'only' 32 kg and #2 if at goal weight I am ravishingly hungry, I'll increase my protein and apple intake and see how that goes.

apressler3

OK, I just finished reading through the full text of the study. Interesting, and a lot more nuanced than the Stat News article. The hot button issue seems to be the claim that losing weight does not seem to "correct" the brain response to nutrient intake. Let me point out a few things.

1. The study shows there is a physiological difference between the two groups and a 10% weight loss does not correct it - important insight with a limited scope. A group that started obese and lost 10% is not the same as a group that started obese and is now lean. The obese group all had BMI > 30, while the lean group had BMI < 25. The obese group lost 10% of body weight in 12 weeks, and were tested pre and post intervention. So far so good. But keep in mind this means they found a 10% decrease in weight did not cause the brain response of the obese group to look like that of the lean group. As an illustration, I have lost about 10% of my body weight since the beginning of the year going from about 310 to 280, and my BMI is still 38. Would it be reasonable to expect my brain response to be the same as that of a person with a BMI of 24? Maybe if the dieted group got their BMI under 25 they would respond similarly. Maybe not.
2. At least one other study, with greater weight loss, did show "improvement" in the brain response. Here's a quote from the paper, emphasis mine:

Here, however, we show that a 12-week supervised dietary intervention promotes significant weight loss and metabolic improvement, but does not restore the physiological brain response to post-ingestive glucose or lipids in humans with obesity, at least during the time course of this study. We reported earlier on a significant increase in striatal D2/3R availability upon weight loss22, but in that study weight loss was higher and induced by bariatric surgery and the interval between baseline and follow-up SPECT was 2 years compared to 12 weeks in the current study.

3. The study injected macronutrient liquid solutions into the stomach via a feeding tube. This is great for control purposes when testing with an MRI machine, but not necessarily applicable to a patients life post diet. I'm not disputing the scientific validity of this approach, merely noting that other attributes of food intake affect hunger and satiety such as protein and fiber. Other studies of people who have lost high proportion of body weight and maintained it for two or more years find that they tend to eat lower fat, higher fiber and protein diets than people who did not successfully maintain.
4. The study also looked at hormone responses, and found the weight loss did change things. Measuring the response to doses of glucose and lipids, insulin and grehlin levels of the obese group looked more like those of the lean group after weight loss than before. GLP-1 levels were lower.

Having said all that, it's nice to have a study showing there is some physiological basis to my lived experience. I don't think there is enough in this one study to claim these physiological patterns cannot be changed. Furthermore, these exciting new research tools may be able to find the optimal path forward.

EDIT: Here's a link to the second study referenced in item 2 above:
Striatal dopamine D2/3 receptor availability increases after long-term bariatric surgery-induced weight loss