Read Original Release

Did study really show that “fasting may reduce breast cancer risk”?

Overnight Fasting May Reduce Breast Cancer Risk in Women

Our Review Summary

AssociationThe headline, “Overnight Fasting May Reduce Breast Cancer Risk in Women,” suggests that an association between fasting and breast cancer was studied.  (Actually, with the words “may reduce,” it suggests that a causal link may have been established, which is not the case.)

But the release does not show any data to support even an association. It appears the study merely hypothesized that the benefits of fasting may be associated with breast cancer reduction, but this hypothesis was not directly tested by the researchers. The release provides no evidence that the researchers looked at actual breast cancer risk in the subjects. We’re only told about “fasting associated with a 4 percent lower postprandial glucose level” – a surrogate, perhaps, but not the risk described in the headline.


Why This Matters

It’s misleading to claim that a study may show a new way to reduce breast cancer risk when, in fact, no such evidence is presented.


Does the news release adequately discuss the costs of the intervention?

Not Applicable

We will rule this criterion Not Applicable in this case because the intervention in question is fasting, which costs nothing.

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

Not Satisfactory

The news release discusses how increasing nighttime fasting is associated with a lower postprandial glucose level, but there is no discussion about how this is associated with a reduced breast cancer risk. This is a significant gap that needed to be addressed.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

There was no discussion of any potential harms associated with increasing the time periods between eating and decreasing overall calorie consumption. The mean duration of nighttime fasting in the study was 12 hours, with discussion of “each three hour increase in nighttime fasting” being associated with a lower glucose level.  It makes one wonder – but the release doesn’t address this – just how long some women in the study fasted.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

There is no discussion of possible limitations of the study.  From what we read in the news release, the researchers are merely speculating about the impact of lower glucose levels and calorie intake. The release provides no evidence that the researchers looked at actual breast cancer risk in the subjects.

We’re only told about “fasting associated with a 4 percent lower postprandial glucose level” – a surrogate, perhaps, but not the risk described in the headline. The assumption is that by lowering blood glucose or keeping it in a lower state, you reduce insulin production, decrease chronic inflammation and mediator release, and can potentially reduce breast cancer development. But obviously many other factors are at play, and it’s never going to be as simple as lowering glucose = less breast cancer.

Does the news release commit disease-mongering?

Not Satisfactory

There was no overt disease-mongering in the news release.  But there is an element of it in the researcher’s quote: “This is a simple dietary change that we believe most women can understand and adopt.”  This implies a suggestion then, that most women should consider fasting longer at night to reduce risk. That smacks of disease-mongering. 

Does the news release identify funding sources & disclose conflicts of interest?


Funding sources are clearly stated at the end of the press release. There are no apparent conflicts of interest.

Does the news release compare the new approach with existing alternatives?


The researchers state that “limiting consumption of red meat, alcohol and refined grains while increasing plant-based foods” reduce breast cancer risk, which is enough to earn the release a satisfactory rating. But we’d note that obesity after menopause is another factor associated with increased risk, one that may be reduced through caloric moderation/restriction and maintenance of a healthy body weight. The release noted that participants who had longer fasting durations had a lower caloric intake, but it did not suggest that the lower calorie intake alone might be a factor in lowering breast cancer risk. That additional context would have been useful.

Does the news release establish the availability of the treatment/test/product/procedure?

Not Applicable

Again, we’ll rule this criterion Not Applicable.  Fasting is something that anyone could do, although some people should consult with a doctor before limiting their calorie intake or increasing the amount of time between meals.

Does the news release establish the true novelty of the approach?

Not Satisfactory

This is a tough call.  The news release quotes a researcher saying “Increasing the duration of overnight fasting could be a novel strategy to reduce the risk of developing breast cancer.”

So that is a claim of novelty.  But that claim – and the association – are not explained adequately in the release. All they showed is that increasing the fasting interval decreases glucose levels and calorie intake.  For that reason, we’ll rule it Not Satisfactory.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?

Not Satisfactory

The headline – by stating that fasting may be associated with breast cancer risk reduction – implies that the release is going to show evidence to support this statement. It didn’t.

Total Score: 2 of 8 Satisfactory

Comments (1)

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Dr. Krishna Kumari Challa

April 23, 2015 at 9:09 pm

Loved this! I myself have written several times to news papers here in India showing them how faulty their reports were. But as usual they ignore all the constructive criticisms and go about their shoddy work gleefully. You are doing this with a good intention. But how many will take notice of it and do the course corrections is a million dollar Q. Keep up the good work. You have all my support.