A month of Ramadan fasting nudges cholesterol the right way, just barely

Every year, millions of healthy adults fast from dawn to sunset for a month during Ramadan, going without food and drink through the daylight hours. Whether this rhythm helps or harms the heart and metabolism has been studied for decades, mostly in small studies with mixed conclusions. Cholesterol, triglycerides, blood pressure and heart rate are the markers used to gauge cardiovascular risk, so a clearer answer matters both to people who fast for faith and to anyone curious about time-restricted eating more generally. This review set out to pool everything published since the field began.

The authors searched ten scientific databases from 1950 to the end of November 2020 for studies of healthy adult Muslims observing Ramadan fasting, which runs for 29 to 30 consecutive days. They identified 91 eligible studies, conducted between 1982 and 2020 in 23 countries across four continents, covering 4431 adults aged 18 to 85. They pooled changes in total cholesterol, triglycerides, HDL, LDL and VLDL cholesterol, diastolic blood pressure and heart rate, then used meta-regression to test whether age, sex and the length of the daily fast moderated the results.

The overall picture was of small favourable shifts rather than dramatic change. HDL cholesterol, the so-called good cholesterol, rose, and LDL cholesterol fell, both by small amounts. Total cholesterol, triglycerides, VLDL cholesterol, diastolic blood pressure and heart rate also trended in a favourable direction, but the effect sizes were modest throughout. The meta-regression suggested that age moderated the changes in HDL and VLDL cholesterol, that sex was linked to the LDL change, and that the daily fasting duration moderated HDL at the end of Ramadan.

The authors conclude that Ramadan fasting positively affects cardiometabolic risk factors and may confer short-term, transient protection against cardiovascular disease in healthy people. The word transient matters: nothing here shows the changes persist once normal eating resumes. The review also cannot untangle the fasting itself from everything else that shifts during Ramadan, including meal composition, sleep and activity. How the findings translate to other intermittent fasting schemes, which differ in timing and in whether fluids are allowed, remains an open question.

If you fast for Ramadan, this is evidence that a month of daytime fasting is, on average, gently kind to the standard heart-risk numbers rather than harmful. The improvements were small, so they are not a reason to treat fasting as a cholesterol fix, and there is no evidence here that they outlast the month. For readers interested in intermittent fasting more broadly, this pattern, no food or drink in daylight for 29 to 30 days, is quite specific, so translating it to other schedules deserves caution.