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Allaf M, Elghazaly H, Mohamed OG, et al. Intermittent fasting for the prevention of cardiovascular disease. Cochrane Database Syst Rev. 2021 Jan 29;1:CD013496. doi: 10.1002/14651858.CD013496.pub2. (Systematic review)
Abstract

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death worldwide. Lifestyle changes are at the forefront of preventing the disease. This includes advice such as increasing physical activity and having a healthy balanced diet to reduce risk factors. Intermittent fasting (IF) is a popular dietary plan involving restricting caloric intake to certain days in the week such as alternate day fasting and periodic fasting, and restricting intake to a number of hours in a given day, otherwise known as time-restricted feeding. IF is being researched for its benefits and many randomised controlled trials have looked at its benefits in preventing CVD.

OBJECTIVES: To determine the role of IF in preventing and reducing the risk of CVD in people with or without prior documented CVD.

SEARCH METHODS: We conducted our search on 12 December 2019; we searched CENTRAL, MEDLINE and Embase. We also searched three trials registers and searched the reference lists of included papers. Systematic reviews were also viewed for additional studies. There was no language restriction applied.

SELECTION CRITERIA: We included randomised controlled trials comparing IF to ad libitum feeding (eating at any time with no specific caloric restriction) or continuous energy restriction (CER). Participants had to be over the age of 18 and included those with and without cardiometabolic risk factors. Intermittent fasting was categorised into alternate-day fasting, modified alternate-day fasting, periodic fasting and time-restricted feeding.

DATA COLLECTION AND ANALYSIS: Five review authors independently selected studies for inclusion and extraction. Primary outcomes included all-cause mortality, cardiovascular mortality, stroke, myocardial infarction, and heart failure. Secondary outcomes include the absolute change in body weight, and glucose. Furthermore, side effects such as headaches and changes to the quality of life were also noted. For continuous data, pooled mean differences (MD) (with 95% confidence intervals (CIs)) were calculated. We contacted trial authors to obtain missing data. We used GRADE to assess the certainty of the evidence.  MAIN RESULTS: Our search yielded 39,165 records after the removal of duplicates. From this, 26 studies met our criteria, and 18 were included in the pooled analysis. The 18 studies included 1125 participants and observed outcomes ranging from four weeks to six months. No studies included data on all-cause mortality, cardiovascular mortality, stroke, myocardial infarction, and heart failure at any point during follow-up. Of quantitatively analysed data, seven studies compared IF with ab libitum feeding, eight studies compared IF with CER, and three studies compared IF with both ad libitum feeding and CER. Outcomes were reported at short term (= 3 months) and medium term (> 3 months to 12 months) follow-up. Body weight was reduced with IF compared to ad libitum feeding in the short term (MD -2.88 kg, 95% CI -3.96 to -1.80; 224 participants; 7 studies; low-certainty evidence). We are uncertain of the effect of IF when compared to CER in the short term (MD -0.88 kg, 95% CI -1.76 to 0.00; 719 participants; 10 studies; very low-certainty evidence) and there may be no effect in the medium term (MD -0.56 kg, 95% CI -1.68 to 0.56; 279 participants; 4 studies; low-certainty evidence). We are uncertain about the effect of IF on glucose when compared to ad libitum feeding in the short term (MD -0.03 mmol/L, 95% CI -0.26 to 0.19; 95 participants; 3 studies; very-low-certainty of evidence) and when compared to CER  in the short term: MD -0.02 mmol/L, 95% CI -0.16 to 0.12; 582 participants; 9 studies; very low-certainty; medium term: MD 0.01, 95% CI -0.10 to 0.11; 279 participants; 4 studies; low-certainty evidence). The changes in body weight and glucose were not deemed to be clinically significant. Four studies reported data on side effects, with some participants complaining of mild headaches. One study reported on the quality of life using the RAND SF-36 score. There was a modest increase in the physical component summary score.

AUTHORS' CONCLUSIONS: Intermittent fasting was seen to be superior to ad libitum feeding in reducing weight. However, this was not clinically significant. There was no significant clinical difference between IF and CER in improving cardiometabolic risk factors to reduce the risk of CVD. Further research is needed to understand the safety and risk-benefit analysis of IF in specific patient groups (e.g. patients with diabetes or eating disorders) as well as the effect on longer-term outcomes such as all-cause mortality and myocardial infarction.

Ratings
Discipline Area Score
Nurse 6 / 7
Physician 5 / 7
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Comments from MORE raters

Nurse rater

Due to obesity in the US, there are always diets and activities to help weight control and increase activity. I found this review excellent as it confirmed that the alternate dietary suggestions are helpful but not significant statistically speaking. There is not a magic pill for weight loss.

Nurse rater

As the study shows, there exists a considerable degree of questionable evidence. It would be helpful if international health organizations, as well as CVD associations, prompt CV researchers to do more coordinated work in this field to narrow down variations and allow for more generalizable findings.

Nurse rater

The information is helpful given the updates and continuous changes in diet and ways to improve risks for CVD.

Nurse rater

I found this article informative from a personal and professional perspective. I have patients asking me about dietary advice regarding eating plans etc (Heart Failure patients) and so it is good to have some evidence behind my answer.

Nurse rater

This is a very current topic and many patients are trying this so this was very helpful.

Nurse rater

This is a very interesting study; although, the result does not reveal as much new or conclusive information.

Physician rater

There were no POEMs (Patient Oriented Endpoints that Matter) here. Intermittent fasting is fashionable but lacks solid evidence that health is indeed improved.

Physician rater

This review has low level evidence of no benefit from calorie restriction compared with intermittent fasting. No surprises.

Physician rater

This is a well done SR. Intermittent fasting may help people to lose more weight than 'eating as usual' (not dieting) but was similar to energy restriction diets. It doesn't find enough good certainty evidence to know whether intermittent fasting could prevent CVD.

Physician rater

Although there is conflicting data on the usefulness of intermittent fasting on the role of intermittent fasting on metabolic and cardiovascular disorders, this Cochrane review sheds more light on the issue. More, larger scale studies are needed to be sure about the potential benefits as suggested by the reviewers.
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