Thursday, 5 January 2012

Does this hypothalamus make me look fat?

We've all had those moments in life when the mirror has been less than kind. When for whatever reason it's decided to add those few extra pounds when just weeks earlier we could have graced the cover of almost any magazine on offer. Or at the very least still fit into our jeans. And so the dieting begins. Caloric intake is restricted and a strict exercise regime is followed. Well maybe not strict, but walking is now done at a brisk pace rather than the meander of old. And then it happens. Like the tides retreating back to sea, our waistline begins to slowly subside. Until finally the top button on our jeans once again remains firmly in place. Life is good. For a month or so. And then. One day. Just like that. The pounds are back. Sound familiar?

So why is it that the weight always seem to find a way to get back into our lives? Were we not motivated enough? Did we not create a big enough support system? Or were all those years filled with cheese and wine just too hard to shake? Whilst it could be argued that any one of these factors may have played a role in it's return, it turns out that the main reason the fat is back, is all in our heads. That's right our brains are making us fat... Again. And here's the second blow. They're so keen to ensure that our biological saddle bags are packed and ready to go that they've developed not one, but two different methods of doing it. Two!



How our brains are making us fat...again.



To be fair it's not the entire brain which is behind this malevolent scheming, but a rather small, pearl-sized area known as the hypothalamus. But how does it do it? Well the first method in which the hypothalamus leads to weight regain is through the release of hormones. A recent Australian study investigated weight gain after dieting in 50 individuals with body mass indices (BMIs) ranging from 27 to 40 and an average weight of 95kg (or around 210lb for those preferring imperial). The researchers measured the levels of appetite-regulating hormones, such as leptin, ghrelin and gastric inhibitory polypeptide, before and after a 10-week low energy diet. As well as once more a year after the program had commenced. What they found was that following initial weight losses of around 13kg (or 29lb), the levels of appetite-regulating hormones coursing through the veins of the dieters had tweaked themselves to induce increased appetite. Making matters worse these hormones remained at their appetite increasing levels for at least a year, helping participants to put an average of 5kg (11lb) of weight back on.


Adding injury to insult



The second manner in which the hypothalamus appears to be conspiring to prevent our slender new bodies from becoming a permanent fixture involve, what some would call, more drastic measures. Not satisfied with its hormonal meddling, it would appear that the hypothalamus develops injuries in response to high fat diets (HFD). According to the study, published in the Journal of Clinical Investigation, both mice and rats, predisposed to obesity, showed evidence of hypothalamic inflammation within as little as 24 hours of being commenced on a HFD. The inflammatory response observed in the rodents' hypothalamic region, or more specifically the hypothalamic arcuate nucleus, were produced in response to neuronal injury, which were in turn thought to be induced by the consumption of the HFD. When the rats were taken off these diets, after only a few days, their injured hypothalamuses were able self-repair. When the HFDs were sustained however the neuronal injuries were also sustained.

Satisfied of their findings in rodents, the researchers turned their gaze toward their fellow humans, and performed MRIs on 34 participants. Just as in fat rats, the hypothalami of obese participants showed evidence of neuronal injury, with larger particpants showing greater areas of scarring. 


No need to panic just yet



Now it should probably be noted that whilst startling these results don't actually prove cause and effect. Nor do they indicate how long a HFD can be consumed before damage becomes irreversible. So there's no need to put the chocolate down just yet. 

The studies do however indicate that maybe it's time for us to change the way we approach the problem of obesity. Firstly there's little doubt that there will be a deluge of post-diet hormonal therapies popping up at pharmacy counters near you in the next few years. So begin preparing yourself for the horrendous ad campaigns that will no doubt accompany them. Secondly whilst our years of cheese and wine may suggest that it's too late for us to reverse any damage done, it's not for the kids. And with the knowledge that housework is a great way to burn calories, you might as well put the little rascals to work now. They'll thank you for it later. Well maybe.




Sources

  • Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A, & Proietto J (2011). Long-term persistence of hormonal adaptations to weight loss. The New England journal of medicine, 365 (17), 1597-604 PMID: 22029981
  • Thaler JP, Yi CX, Schur EA, Guyenet SJ, Hwang BH, Dietrich MO, Zhao X, Sarruf DA, Izgur V, Maravilla KR, Nguyen HT, Fischer JD, Matsen ME, Wisse BE, Morton GJ, Horvath TL, Baskin DG, Tschöp MH, & Schwartz MW (2011). Obesity is associated with hypothalamic injury in rodents and humans. The Journal of clinical investigation PMID: 22201683

Images

This post was written by Andrew Watt for A Hippo on Campus.

4 comments:

  1. This blog is fantastic. Thank you for putting all of the time into writing such interesting, well informed articles!

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  2. I'm consistently amazed at the products that come out to assist with weight loss. Haven't seen many related to maintenance, but I'm sure we will, as more of the hormonal realities become known. I, for one, am looking forward to the tired, supposedly easy "eat less/move more" meme to lose some traction, if only for the attitude change it might help bring about.

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  3. @justjuliebean'm sure it's only a matter of time before 'No pain / No gain' is replaced by an equally catchy war-cry from the hormonal pill-pushers. Or perhaps we'll be seeing the return of the ever popular tape-worm in a pill. Either way it feels like that paradigm shift might be just around the corner.

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  4. @MelissaMy pleasure Melissa, I'm glad you're enjoying it.

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