On Second Thought : Intermittent Fasting

"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.]"

"[We -- he and colleagues -- conducted the study to see how eating within a daily narrow window might impact] hard end points [like heart disease and mortality.]"

"We had expected that long-term adoption of eight-hour time restricted eating would be associated with a lower risk of cardiovascular death and even all-cause death."

Victor Wenze Zhong, chair, department of epidemiology and biostatistics, Shanghai Jiao Tong University School of Medicine, China

 

What qualifies as intermittent fasting is the popular dietary choice trending by people to eat only at certain times of the day. Dr. Zhong's study results are fairly sobering; suggesting caution is called for in committing to the concept, given the takeaway from the results he and his colleagues tabulated; findings that were presented at an American Heart Association meeting that took place in Chicago last month, focused on the concept of eating meals in just eight hours or less, with a 16-hour daily fast, known as 'time-restricted' eating.

 

Data on the dietary habits of 20,000 adults across the United States were analyzed, of those the study followed from 2003 to 2018. People who adhered to the eight-hour eating plan were found to have a 91 percent higher risk of dying from heart disease, in comparison to those following a traditional dietary pattern, eating food across 12 to 16 hours daily. This increased risk also applied to those already living with a chronic disease or cancer.  

Individuals with existing cardiovascular disease -- found the study group -- who followed a time-restricted eating pattern had a 66 percent higher risk of dying from heart disease or stroke, and those with cancer were likelier to die of the disease if they followed a time-restricted diet in comparison to people with cancer who followed an eating duration of at least 16 hours daily. People who practice intermittent fasting for lengthy periods, in particular those with existing heart conditions or cancer, suggests the study results, should be "extremely cautious", warned Dr. Zhong.

Despite the findings, the study results fail to explain why it is that time-restricted eating has such a profound impact on people's health risks, but the researchers found that those following a 16:8 time-restricted eating pattern had less lean muscle mass in comparison to individuals who eat throughout longer daily periods, lining up with a previous clinical trial published in JAMA Internal Medicine. That trial found people assigned to follow a time-restricted diet for three months lost more muscle than a control group not assigned to intermittent fasting.

Having low muscle mass is linked to higher mortality rates, including a higher risk of dying from heart disease, according to studies. However, Dr. Zhong stresses the findings of his study were not definitive. While the study uncovered a correlation between time-restricted eating and increased mortality, it could not show cause and effect. Health experts and celebrities have been extolling the presumed virtues of the plan, citing a variety of health benefits. 

Some early studies on time-restricted eating found it helped to prevent laboratory mice from developing obesity and metabolic syndrome. There were for the most part small clinical trials in humans that followed, some of which indicated that time-restricted eating helped people lose weight and improve blood pressure, blood sugar and cholesterol levels. Some of these studies, short-term -- lasting between one to three months, in some instances showed no benefit.

A more rigorous study of time-restricted eating published in the New England Journal of Medicine in 2022, found that obese people assigned to follow a low-calorie diet, instructed to eat only between the hours of 8 a.m. and 4 p.m. daily, lost no greater weight than people eating a like number of calories throughout the day, with no time restrictions. Both diets held similar effects on blood pressure, blood sugar, cholesterol and other metabolic markers, suggesting any benefits of time-restricted eating result in all likelihood from consuming fewer calories.

New study found intermittent fasting may deleteriously impact the heart. WashingtonPost.com