Pros, cons of intermittent fasting

(MENAFN) Intermittent fasting has surged in popularity as a diet trend, promising health benefits without the need for strict calorie counting or eliminating certain foods. By simply adjusting the timing of meals rather than their content, the approach has won followers among tech leaders, Hollywood celebrities, and public figures. Former UK Prime Minister Rishi Sunak, for example, has mentioned starting his week with a 36-hour fast.

Previous research suggested that extending the overnight fasting period could enhance metabolism, support cellular repair, and potentially extend lifespan. However, nutrition experts have long cautioned that skipping meals is not a universal solution and may carry risks for those with preexisting conditions.

Intermittent fasting typically involves compressing daily eating into a short window, often eight hours, leaving a 16-hour fasting period. Other time-restricted approaches, such as the 5:2 plan, limit calories on specific days rather than restricting hours of intake.

Now, a large-scale study analyzing data from over 19,000 adults raises concerns about cardiovascular health. Researchers found that individuals who confined their eating to less than eight hours daily faced a 135% higher risk of dying from heart and blood vessel-related diseases compared with those spreading meals over 12-14 hours. While the study observed only a weak and inconsistent link between time-restricted eating and overall mortality, the increased risk of cardiovascular death remained consistent across age, sex, and lifestyle groups.

The study’s authors caution that the findings do not prove cause and effect but signal a need to reconsider the narrative that fasting is entirely risk-free. Participants’ eating patterns were assessed through dietary recalls on two separate days, which were then used to estimate average eating windows. Elevated cardiovascular risk was observed across socioeconomic groups, particularly among smokers and those with diabetes or preexisting heart conditions, even after adjusting for diet quality, meal frequency, and other lifestyle factors.

Victor Wenze Zhong, the study’s lead author, noted that “The unexpected finding is that sticking to a short eating window less than eight hours over years was linked to increased death risk from cardiovascular disease.” This contrasts with short-term studies that suggested fasting improves heart and metabolic health.

In an accompanying editorial, endocrinologist Anoop Misra highlights both potential benefits and risks. Intermittent fasting can promote weight loss, improve insulin sensitivity, lower blood pressure, enhance lipid profiles, and offer anti-inflammatory effects. It may also simplify blood sugar management and align with cultural or religious fasting practices.

“However, the potential downsides include nutrient deficiencies, increased cholesterol, excessive hunger, irritability, headaches and reduced adherence over time,” Misra said. He warns that for people with diabetes, unmonitored fasting may cause dangerous drops in blood sugar and encourage unhealthy food choices, while older adults or those with chronic conditions could face increased frailty or muscle loss.

Past studies have already questioned the effectiveness of fasting. A three-month trial published in 2020 found minimal weight loss, much of which may have been muscle. Other research has noted side effects including weakness, dehydration, headaches, and difficulty concentrating.

Prof Zhong advises caution for those with heart disease or diabetes considering an eight-hour eating window. The findings underscore the importance of personalized dietary guidance based on individual health. “Based on the evidence as of now, focusing on what people eat appears to be more important than focusing on the time when they eat. At least, people may consider not to adopt eight-hour eating window for a long time either for the purpose of preventing cardiovascular disease or for improving longevity.”

For now, the recommendation is less about abandoning intermittent fasting and more about tailoring it to individual risk profiles. Until further evidence emerges, prioritizing food quality over strict eating schedules may be the safest approach.

MENAFN01092025000045017281ID1110000993