Intermittent fasting continues to be one of the most talked about dietary strategies, so in this blog we are gradually compiling the evidence that is published on the subject. And last week a review was published that I think is worth mentioning, because it is carried out by Cochrane, an independent entity specialized in carrying out particularly rigorous systematic reviews in the field of health.
The work is titled «Intermittent fasting for the prevention of cardiovascular diseases» (2021) and synthesizes the results of trials on intermittent fasting – in any of its modalities – in which its effect on the risk of cardiovascular disease and its associated indicators (body composition and weight, blood pressure, lipids) have been analyzed. and blood glucose and inflammation), carrying out an evaluation of the level of existing evidence.
The entire extensive and detailed document can be downloaded at this link and will surely be of interest to more advanced readers. But since Cochrane has the good habit of publishing a summary of the conclusions of his reviews in accessible language, I will translate below the text with said summary.
Here it is:
«We found 26 relevant studies; we used results from 18 of the studies to compare the different modalities. The 18 studies included 1,125 adults (over 18 years old). Some people in the studies had risk factors for cardiovascular disease and others did not have risk factors. Most of the studies were funded by universities and research centers; two studies were funded by companies that make diet foods.
The studies compared intermittent fasting versus a regular diet (seven studies), versus energy restriction (eight studies), and versus a regular diet and energy-restricted diet mixed (three studies). The studies lasted from four weeks to six months. Results were reported after three months (short term) and between three and 12 months (medium term).
We did not find any data on mortality, cardiovascular mortality, or risk of stroke, heart attack, or heart failure.
We found that people can lose more weight on intermittent fasting than on a regular diet for three months (evidence from seven studies in 224 people); but not compared to energy-restricted diets for three months (ten studies; 719 people) or longer (three to 12 months; four studies; 279 people).
We found that intermittent fasting did not appear to affect blood glucose levels compared to the usual diet for three months (3 studies; 95 people); energy-restricted diets for three months (nine studies; 582 people); or energy-restricted diets for 3 to 12 months (4 studies; 279 people).
The weight losses and changes in blood glucose reported in the studies were small. These changes are not considered clinically significant.
Only four studies reported unwanted effects of intermittent fasting: some people who participated reported mild headaches. Only one study reported on people’s well-being, showing a small increase in assessments of physical well-being.
Our confidence in the results
We don’t trust the results. We found limitations in the way studies are designed, conducted, and reported; and in some studies, results varied widely or were inconsistent. Our results are likely to change if more evidence becomes available.
Key messages
We did not find enough certainty to know whether intermittent fasting could prevent cardiovascular disease. We found that intermittent fasting can help people lose more weight than «eating as usual» (not dieting), but it was similar to energy restriction diets. We need more research to test the potential benefits and harms of intermittent fasting and to test whether it might affect the risk of mortality or cardiovascular disease.
Authors’ conclusions
It will be noted that intermittent fasting was superior to ad libitum feeding for weight reduction. However, it was not clinically significant. There was no clinically significant difference between intermittent fasting and equivalent caloric restriction in improving cardiometabolic risk factors to reduce the risk of cardiovascular disease. More research is needed to examine the risk-benefit ratio in specific patient groups (for example, patients with diabetes or eating disorders), as well as the effect on longer-term outcomes, such as all-cause mortality and stroke. . of myocardium.»
In short, the authors conclude that the existing evidence is scarce and that the only effect that they have been able to confirm with some reliability has been a small reduction in weight (clinically not significant) compared to the usual diet (that is, «without dieting»). ). They have found no evidence of significant effects on other indicators related to cardiovascular disease (body composition and weight, blood pressure, lipids and blood glucose, and inflammation) nor advantages over a diet with equivalent caloric restriction.
Update:
A few weeks after this research, another systematic review on the topic was published, «A systematic review of the association between vegan diets and the risk of cardiovascular disease» (2021). Its conclusions were similar: little evidence of the effects of a vegan diet on cardiovascular diseases.
