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Behold, firm evidence — at last — that ultra-processed food causes weight gain

Junk food causes weight gain, but it's not just about the calories.

Photo Illustration by Justin Sullivan / Getty Images

We know we should eat less junk food, such as crisps, industrially made pizzas and sugar-sweetened drinks, because of their high calorie content.


These “ultra-processed" foods, as they are now called by nutritionists, are high in sugar and fat, but is that the only reason they cause weight gain? An important new trial from the U.S. National Institute of Health (NIH) shows there's a lot more at work here than calories alone.

Studies have already found an association between junk foods and weight gain, but this link has never been investigated with a randomized controlled trial (RCT), the gold standard of clinical studies.

In the NIH's RCT, 20 adults aged about 30 were randomly assigned to either a diet of ultra-processed foods or a “control" diet of unprocessed foods, both eaten as three meals plus snacks across the day. Participants were allowed to eat as much as they wished.

After two weeks on one of the diets, they were switched to the other for a further two weeks. This type of crossover study improves the reliability of the results since each person takes part in both arms of the study. The study found that, on average, participants ate 500 calories more per day when consuming the ultra-processed diet, compared to when eating the diet of unprocessed foods. And on the ultra-processed diet, they gained weight — almost a kilogram.

Although we know that ultra-processed foods can be quite addictive, the participants reported finding the two diets equally palatable, with no awareness of having a greater appetite for the ultra-processed foods than for the unprocessed foods, despite consuming 500 calories more of them per day.

Unconscious over-consumption of ultra-processed foods is often attributed to snacking. But in this study, most of the excess calories were consumed during breakfast and lunch, not as snacks.

Slow eating, not fast food

A crucial clue as to why the ultra-processed foods caused greater calorie consumption may be that participants ate the ultra-processed meals faster and so consumed more calories per minute. This can cause excess calorie intake before the body's signals for satiety or fullness have time to kick in.

An important satiety factor in unprocessed foods is dietary fibre. Most ultra-processed foods contain little fibre (most or all of it is lost during their manufacture) and so are easier to eat fast.

Anticipating this, the NIH researchers equalized the fiber content of their two diets by adding a fibre supplement to the ultra-processed diet in drinks. But fibre supplements are not the same thing as fibre in unprocessed foods.

Fibre in unprocessed food is an integral part of the food's structure – or the food matrix, as it's called. And an intact food matrix slows down how quickly we consume calories. For instance, it takes us far longer to chew through a whole orange with its intact food matrix than it does to gulp down the equivalent calories as orange juice.

An interesting message emerging from this and other studies seems to be that to regulate calorie intake, we must retain food structure, like the natural food matrix of unprocessed foods. This obliges us to eat more slowly, allowing time for the body's satiety mechanisms to activate before we have eaten too much. This mechanism does not operate with ultra-processed foods since the food matrix is lost during manufacture.

Finding time for a meal of unprocessed foods eaten slowly can be a real challenge for many. But the importance of seated mealtimes is an approach vigorously defended in some countries, such as France, where a succession of small courses ensures a more leisurely — and pleasurable — way of eating. And it may also be an important antidote to the weight gain caused by grabbing a quick meal of ultra-processed foods.The Conversation

Richard Hoffman, Lecturer in Nutritional Biochemistry, University of Hertfordshire

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hulu's original movie "Palm Springs" is the comedy we needed this summer

Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.

Gear
  • Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
  • As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
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Two MIT students just solved Richard Feynman’s famed physics puzzle

Richard Feynman once asked a silly question. Two MIT students just answered it.

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Our ‘little brain’ turns out to be pretty big

The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
Mind & Brain
  • A powerful MRI combined with modeling software results in a totally new view of the human cerebellum.
  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

Economists show how welfare programs can turn a "profit"

What happens if we consider welfare programs as investments?

A homeless man faces Wall Street

Spencer Platt/Getty Images
Politics & Current Affairs
  • A recently published study suggests that some welfare programs more than pay for themselves.
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