Glucose appears to temper brain activity in regions that regulate appetite and reward — but fructose does not, researchers found.
In a brain imaging study, participants who had a drink sweetened with glucose had significant reductions in cerebral blood flow in the hypothalamus, while those who drank a fructose-sweetened drink saw a slight increase in activity (P=0.01), Robert Sherwin, MD, of Yale University, and colleagues reported in the Jan. 2 issue of the Journal of the American Medical Association.
Glucose also reduced activation in the insula and striatum, other brain regions that regulate appetite, motivation, and reward processing, while fructose did not, the researchers wrote.
In an accompanying editorial, Jonathan Purnell, MD, and Damien Fair, PhD, of Oregon Health & Science University in Portland, said the findings “support the conceptual framework that when the human brain is exposed to fructose, neurobiological pathways involved in appetite regulation are modulated, thereby promoting increased food intake.”
As the obesity epidemic has grown, so too has consumption of fructose in the American diet, the researchers explained in their article. Fructose is found in both sucrose, or table sugar, and in high-fructose corn syrup, another common sweetener. It is valued because it’s sweeter than glucose.
But studies show fructose may have different metabolic effects than glucose. For instance, fructose only weakly stimulates secretion of insulin, a hormone that can increase satiety, and attenuates levels of the satiety hormone glucagon-like peptide-1 (GLP-1) — so researchers are concerned that it could possibly increase food-seeking behavior and intake.
To assess those effects, Sherwin and colleagues conducted functional MRIs (fMRIs) in 20 normal-weight, healthy adults who were given 75 grams of either glucose or fructose in a cherry-flavored drink, and then crossed over to a drink with the other sweetener.
Participants rated their feelings of hunger, satiety, and fullness before and after the scan, and the researchers took blood to assess circulating hormone levels.
Overall, the researchers found that glucose significantly reduced cerebral blood flow in the hypothalamus, while fructose did not.
Specifically, blood flow fell 5.45 mL/g per minute from baseline with glucose, compared with an increase of 2.84 mL/g per minute with fructose, for a mean difference of 8.3 ml/g per minute, they reported (P=0.01).
They also found that glucose reduced cerebral blood flow in the thalamus, insula, anterior cingulate, and striatum — “regions that act in concert to ‘read’ the metabolic state of an individual and drive motivation and reward” — compared with baseline (P<0.05).
In contrast, fructose reduced blood flow in the hippocampus, posterior cingulate cortex, fusiform, and visual cortex — but also in the thalamus (P<0.05).
In terms of connectivity between brain regions, glucose upped the links between the hypothalamus and the thalamus and striatum, while fructose only increased connectivity between the hypothalamus and thalamus, but not the striatum — the latter of which also de-activates once a person is sated, the researchers said.
“These findings suggest that ingestion of glucose, but not fructose, initiates a coordinated response between the homeostatic-striatal network that regulates feeding behavior,” they wrote.
They also found that glucose, but not fructose, had effects on circulating “hunger” hormone levels. Glucose elevated levels of insulin and GLP-1 compared with fructose (P<0.001 and P=0.01, respectively).
Leptin and ghrelin levels, however, weren’t significantly different between the two sugars, the researchers found.
The differences in brain effects between glucose and fructose also appeared to coordinate with ratings of hunger, since there was a significant difference from baseline in terms of fullness and satiety when participants drank glucose, but not fructose (P=0.005 and P=0.03, respectively).
Sherwin and colleagues cautioned that the study was limited because fMRI doesn’t provide a direct measure of neuronal activity, and thus any clinical implications can’t yet be determined.
Editorialists Purnell and Fair noted that while some researchers and clinicians warn that the total amount of calories is more important than the type of food when it comes to losing weight, the “reality … is that hunger and fullness are major determinants of how much humans eat, just as thirst determines how much humans drink. These sensations cannot simply be willed away or ignored.”
“The remedy remains eating less,” they wrote, “but the means involve reducing the food element, if possible.”
By Kristina Fiore, Staff Writer, MedPage Today
Today Andy Burnham MP critisized levels of sugar in children’s cereals where some brands including favourites such as Kellogg’s Frosties, Sugar Puffs and Coco Pops have up to near 40% sugar content. I would like to say thank you to Mr Burnham MP for re-igniting this debate, however, I hope if he ever becomes Health Minister again I hope he sticks to his beliefs and not cave in under pressure from the food industry lobbyists.
Read Daily Telegraph article here.
A doctor who is also a Conservative MP (Phillip Lee) has been calling for obese people to contribute to their medical bills if they need treatment that is related to their condition, e.g. Type 2 Diabetes. Sounds good in theory because as we all know obese people are all just greedy gluttons who can’t help but stuff armfuls of food down their necks…Yes there are people who make the wrong food choices but Dr Lee has not looked under the surface for possible causes of this obesity epidemic. There are reasons as to why a person is obese but I guess it is easier to blame them than look elsewhere – maybe the food industry that effectively lobbies government. Perhaps Dr Lee you should be looking at what crap gets put in our food these days – I’m particularly talking about hidden sugars/fructose (those low fat options for example). There is good evidence that junk food is addictive in the same way as cigarettes and alcohol and the western diet makes you eat more. We are also now seeing obese 6 month old babies. It seems that there is something awry when a baby who isn’t even eating food yet is becoming obese…they can’t be blamed for their obesity can they! I guess Dr Lee would charge for treatment of these babies if they were obese! Ridiculous!
I know we should all be home cooking with fresh ingredients preferably with organic, free range foods, etc. But this option can be far more expensive (particularly if you live in the US) than buying ready made meals for example. Indeed in poor neighbourhoods it’s hard if not impossible to find fresh ingredients at all. This is made especially more difficult if people are trying to survive in this economic climate with pay freezes for those lucky enough to be working and reductions/freezes on welfare payments…
So please please please stop the demonisation of obese people!
YOu couldn’t make it up could you? It transpires that the Pan-American arm of the WHO has been asking the food industry for its advise it tackling obesity…well seems there won’t be any attempt to regulate fizzy drinks then. Coca-Cola, Nestle and Unilever have also bribed sorry donated large amounts of cash to the organisation. Apparently this is a “new ay of doing business”. I suggest this is one of the oldest ways of doing business, i.e. bribe the regulator!
Check out some of the latest research into using fasting to improve your health in terms of stabilising blood sugar, blood pressure, etc. It’s on BBC iplayer for the next month. After this there is a clip on You Tube:
Well it’s good for Big Pharma and their shareholders anyway. Why do I say that? Well just look at the recent $5.3bn acquisition of Amylin Pharmaceuticals Inc. by Bristol-Myers Squibb and AstraZeneca. Amylin produce diabetes drugs Byetta and Bydureon. It is estimated that they will need to make $2bn in peak sales to justify the transaction. Byetta made $518m in sales last year and Bydureon $7m in the first quarter of the year being only approved for sale in January. So looking at the figures they are going to have to do some hard selling to get their money back! Indeed Bristol executives said that while Amylin’s sales force had targeted endocrinologists, the combined sales forces of the three companies would be able to widen their presence to cover primary care physicians.
One endocrinologist I’ve mentioned in previous posts is Dr Robert Lustig who has stated that the lack of fibre in our modern diet combined with too much sugar (and high-fructose corn syrup) is the cause of obesity and diabetes. He believes you can cure type 2 diabetes in a week with a high-fibre diet. But do you think Big Pharma actually cares about this endocrinologists opinion. Hell no. At the end of the day these companies are raking in the profits as more and more people become ill through their poor diet. It’s the same for the food industry. It’s been shown that their lobbying of governments and other agencies forces them to water-down or even shelve reports that would hurt their business. Have a look at these articles where the sugar industry threatened the WHO (World Health Organisation) over a report they drafted recommending reducing a persons sugar intake:
And guess what happened? Yup the WHO recommendations were dropped – check out the video 9 mins in:
Also check out YouTube for all the episodes of The Men Who Made Us Fat – not on BBC iplayer anymore.
Just came across this obesity graphic on Reuters showing the most obese nations. Fine. Underneath this map however is a projection of obesity-related drug sales where the top three drugs Lorcaserin (Arena Phamaceuticals), Qnexa (Vivus Inc) & Contrave (Orexigen Therapeutics) will earn their respective drug companies $755m, $689m & $443m. These drugs, as these companies know full well, ain’t going to help these people, only going to boost their profits. The real solution as highlighted in tonights BBC programme – The Men Who Made Us Fat is the rise of high fructose corn syrup in most processed foods…
Unfortunately, as is well known the food industry has huge power here and in the US so governments are too scared to do anything about it…indeed in the programme it mentioned the industry warning the WHO not to publish a damming report on sugar consumption, which it apparently shelved after being ‘leant on’. Same old. Same old….
Great playlist of videos featuring Prof. Robert Lustig about the real reasons we are where we are with obesity.
I’ll be taking a look at this programme tonight (14th June) at 9pm on BBC2 – The Men Who Made Us Fat. If you can’t watch it tonight be sure to see it on iplayer. It looks like it is concentrating on the real reason we are becoming overweight and obese – the ubiquitous evil substance that is high-fructose corn syrup (HFCS).
The programme blurb mentions the endocrinologist Robert Lustig who was one of the first to notice the dangers of HFCS but was unsurprisingly ignored. If you cannot wait till for tonight’s programme or want to see Prof. Lustig in action telling you how it is (with humour) it’s a great watch especially like the Coca-Cola Conspiracy bit (about 11 mins in). Check it out below. Also it’s worth exploring the rest of UCTV for great lectures on a variety of subject areas.