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 being 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 conducting particularly rigorous systematic reviews in the field of health.
The work is entitled “Intermittent fasting for the prevention of cardiovascular disease” (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 and blood glucose, and inflammation), making an evaluation of the degree of existing evidence.
The full lengthy and detailed document can be downloaded at this link and will surely be of interest to more advanced readers. But since Cochrane has a good habit of publishing a summary of the conclusions of its reviews in accessible language, I will translate the text with that summary below.
Here it is:
“We found 26 relevant studies; we used the results of 18 of the studies to compare the different modalities. The 18 studies included 1,125 adults (over 18 years of age). Some people in the studies had risk factors for cardiovascular disease and others did not. risk factors Most of the studies were funded by universities and research centers, two studies were funded by companies that manufacture dietetic foods.
Studies compared intermittent fasting versus usual diet (seven studies), versus energy restriction (eight studies), and versus mixed usual diet and energy restricted diet (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 usual diet over three months (evidence from seven studies in 224 people); but not when compared to energy-restricted diets for three months (10 studies; 719 people) or longer (3 to 12 months; four studies; 279 people).
We found that intermittent fasting did not appear to affect blood glucose levels compared with usual diet for three months (3 studies; 95 people); energy restriction diets for three months (9 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 were 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 physical well-being scores.
Our confidence in the results
We do not trust the results. We found limitations in the way the studies were designed, conducted and reported; and in some studies, the results varied widely or were not consistent. Our results are likely to change if more evidence becomes available.
key messages
We found insufficient certainty evidence 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-restricted 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
Intermittent fasting was found to be superior to ad libitum feeding in reducing weight. However, it was not clinically significant. There was no clinically significant difference between intermittent fasting and equivalent caloric restriction in improving cardiometabolic risk factors for reducing cardiovascular disease risk. Further research is needed to analyze the risk-benefit ratio in specific groups of patients (for example, patients with diabetes or eating disorders), as well as the effect on longer-term outcomes, such as all-cause mortality and myocardial infarction. 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 weight reduction (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, blood lipids and glucose, and inflammation) or any advantage over an equivalent calorie-restricted diet.
Update:
A few weeks after this research another systematic review on the subject was published, “A Systematic Review of the Association Between Vegan Diets and Risk of Cardiovascular Disease” (2021). Its conclusions were similar: scant evidence of the effects of a vegan diet on cardiovascular disease.