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CNN story on fasting diet study veers into clickbait territory

Story highlights

  • The fasting-mimicking diet is thought to reduce disease risk and improve lifespan
  • The diet involves reducing calories significantly for five consecutive days every three months
  • Fasting can put the body into standby and activate pathways that lead to regeneration of cells

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(CNN)How much — or how little — you eat could influence how long you live.

The idea of caloric control improving your health, and therefore your lifespan, is nothing new, but researchers are now hoping to accurately determine the type of diet that could make you live longer.

One team at the University of Southern California (USC) are reducing the calorie count as low as it can go, using specific foods to trick the human body into thinking it’s fasting — a process called fasting mimicry.

“Diet can have a remarkable effect on you,” says Valter Longo, Professor of Gerontology at USC Davis, who has been long been researching the mechanisms behind human aging and has recently turned his attention to fasting.

“It can reprogram your body and put it on a path to live longer,” says Longo.

Shutdown and regeneration

Fasting has been performed by communities and cultures for millennia and Longo’s team are curious about the advantages.

Their idea follows on from the long running trend of caloric restriction, mostly known through diets such as the 5-2 diet and intermittent fasting. Longo tested the impact of fasting for five consecutive days every month, believing that when the body thinks it’s in a state of fasting, it shuts down and goes into standby mode.

“As cells are killed and the body goes into standby, your stem cells switch on,” says Longo. Once switched on, the stem cells can regenerate the lost cells and organ mass — leaving you shiny and new.

When cells in the body age, their ratios change and Longo believes the body’s reaction — and repair methods — to fasting help restore them to when you were younger. “You’re killing the bad cells and regenerating with cells that are more functional.”

Starvation strategies

In a 2015 study, Longo’s team set a specific diet for human volunteers, which mimicked the effects of fasting over five consecutive days monthly, for three months. Trials were also conducted in mice.

People consumed approximately 1000 calories on day one and 725 calories for the remaining four days, but these numbers alone didn’t determine the benefit.

“It’s not just about reducing calories”, says Longo. His diet is designed to include specific percentages of protein, fat and carbohydrates, for maximum effect. The food items used, however, were specific to the trial and if translated to the public would involve designing meals made up of the right combination of nutrients.

Read more: New protein could help burn fat faster

“The human fasting mimicking diet (FMD) program is a plant based diet program designed to attain fasting-like effects while providing micronutrient nourishment (vitamins, minerals, etc.) and minimize the burden of fasting,” Longo said in the study.

After three months, the benefits were a reduction in body weight as well as certain risk factors for cardiovascular disease. There was also an increase in certain stem cells in the body.

“The diet is turning on the body’s ability to renew itself,” says Longo.

The team have since calculated that following the diet every three months could provide enough of an impact as effects are thought to last up to six months.

How does it work?

“When you fast, you lower protein and certain amino acids and you control pathways [in the body],” says Longo. The pathways he refers to are known as TOR, PKA and IGF pathways, which when controlled can switch on certain reactions inside the body causing immune cells to die and organs to shrink.

This activation, or reduction, of pathways is why the components of the diet, such a proteins, must also be controlled. “You won’t activate the correct pathways,” says Longo.

“When you make IGF less active, it reduces risk factors linked to diabetes and cardiovascular disease,” says Miguel Toribio-Mateas, Chairman of the British Association for Applied Nutrition and Nutritional Therapy.

According to Toribio-Mateas, the results confirm earlier theories that “some hormone-like growth factors that are required during development to grow, then become promoting agents of aging after development and sexual maturity have been reached”. He also believes the benefits are down to improved efficiency on a cellular level.

“Cells have a list of things to do every day,…like getting rid of toxins” says Toribio-Mateas. If their workload is then disrupted by the need to store excess calories, certain products can accumulate. “Regulating calories can have a very positive effect,” he says. To him, diet underpins longevity.

Is it safe?

Unlike the 5-2 diet, which requires two days of low calories at any point in the week, Longo’s diet involves fasting for five consecutive days, which requires much more willpower.

“Five days is safe: going on for longer is difficult to do outside of a clinic,” says Longo.

Read more: Five ways to eat yourself healthier

More work needs to be done to fine tune the diet and determine meals that meet the criteria. Longo has since founded his own nutrition company. L-Nutra, to sell products that serve this purpose, which may be seen as a conflict of interest. He states that profits are going back into funding further research by his team.

“The results of the study are encouraging and warrant more research in this area,” says Toribio-Mateas.

Occasional fasting could help you live longer

Our Review Summary

iStock_000020161847_SmallThis CNN story looks at studies investigating the potential life-extending benefits of periodically fasting, and of consuming a special diet that makes the body think it’s fasting. It glosses over important details like who was studied and how, and instead claims that the diet has the potential to “help you live longer.” That’s an unhelpful, clickbait-y approach to the science that we wish more news outlets would avoid. Extensive passages devoted to medical jargon only serve to confuse the reader, as well.


Why This Matters

Who doesn’t want to live longer? Lose excess weight? Reduce their risk of heart disease? The claims made in this piece are appealing to many of us–and therefore likely to garner a lot of clicks–but they’re also poorly supported by the actual research. That’s dangerous: Readers of this story could very easily make false conclusions about the benefits of fasting, and assume it’s risk-free.


Does the story adequately discuss the costs of the intervention?

Not Satisfactory

Fasting to improve your health sounds like a great way to spend less money on food, and it’s tempting to assume this diet would be cheap to follow. But that doesn’t seem to be the case: The story indicates study participants were fed a custom-designed meal program that would have to be replicated in the general population to achieve the same benefits. This will presumably cost money–but we’re not given any idea of how much that might cost.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

This story is painfully lacking in quantified benefits. How many people were in the study? And what kind of people were they? (Overweight or healthy weight? Male or female?) Were they compared against a control group? How much actual weight did participants lose? What specific aging risk factors were researchers measuring and how much did those improve? Similar information is missing for the mice portion of the study.

We were also dismayed at the extent of medical jargon included in the piece, since uselessly granular details about cellular pathways, cell regeneration and “hormone-like growth factors” don’t provide important details about if this research is actually meaningful and worth reading about. What it does instead is fluff up the piece by making it sound smarter than it actually us.

Does the story adequately explain/quantify the harms of the intervention?

Not Satisfactory

This story should have explained to readers at least a few known potential harms of fasting–which are very real, especially for people with certain health conditions, including common ones like diabetes. All we get is a quote that hints it might be dangerous to fast for more than five days:

“Five days is safe: going on for longer is difficult to do outside of a clinic,” says Longo.

But fasting for 5 days would clearly be harmful for many people.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

The human portion of this study was a pilot trial looking at specific changes in a handful of biomarkers associated with aging, but the story fails to make that clear. What it does instead is jump to the dramatic conclusion (and click-baiting headline) that fasting “could help you live longer.”

Does the story commit disease-mongering?


Aging isn’t a disease–it’s a universal fact of life that happens to all of us. While none of us can avoid aging, we can make changes to age in a more healthful way. This story did seem to stick to that premise, and avoided statements that made aging sound like a disease.

Does the story use independent sources and identify conflicts of interest?


Whoo boy. We’re giving this a satisfactory rating since the story does let us know there is a potential conflict of interest–one of the researchers plans to sell nutrition products promoting this type of dieting. However, we wish this fact would have raised more red flags for CNN, and led to a more critical analysis of the piece.

A second source quoted in the story — nutritionist Miguel Toribio-Mateas — espouses some unorthodox views on his website, including that one can  “grow younger from inside by providing the necessary building blocks that enable cellular processes to keep us looking and feeling our best as we age.”

While we question the source’s expertise, we think the story meets the standard for a Satisfactory rating. But readers should be wary of the guidance being provided, which doesn’t seem to be based on particularly strong evidence.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

This story makes no mention of other ways to achieve similar benefits. How does this dieting approach compare, for example, to regular exercise as a means to age healthier?

Does the story establish the availability of the treatment/test/product/procedure?


The story makes it clear that fasting participants were given a specific type of meal that isn’t available to the general public.

Does the story establish the true novelty of the approach?


The story makes a reference to something called the “5-2” fasting diet but is short on details. If one reads closely enough, it seems that the new diet plan is supposed to achieve the effects of fasting diets without actually fasting. We’ll give the benefit of the doubt on this one, especially since the story acknowledges a history of similar research, for example when it says, “The idea of caloric control improving your health, and therefore your lifespan, is nothing new, but researchers are now hoping to accurately determine the type of diet that could make you live longer.”

Does the story appear to rely solely or largely on a news release?


The story includes quotes from a source not involved in the study, so it appears the story went beyond relying solely on a news release.

Total Score: 5 of 10 Satisfactory

Comments (2)

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Louise Arnison

March 14, 2016 at 11:52 pm

Since you scored the story 5 out of 10 and one of the satisfactory ratings was equivocal, what tipped the scale for you to conclude the story was satisfactory?


Mark Schoene

March 15, 2016 at 9:38 am

This is an excellent review. And the CNN piece deserved its poor score.
However, don’t think the area of intermittent fasting is quite as bereft of scientific evidence as the review indicates. The 5:2 diet is the wildly popular FAST diet, popularized in the UK by Michael Mosley. It hasn’t been studied extensively. However, the FAST diet is a variant on Alternate Day Fasting (developed and studied by nutritionist Krista Varady of U. of Illinois), which does find some scientific support in terms of weight loss, altering blood chemistry, and lowering blood pressure—though in studies of modest size.
This is a lively research area. For those interested, the NIH recently sponsored a workshop on this issue—summarized in this 2014 article in PNAS: