Dr. Shahar Madjar, Journal columnist

What is intermittent fasting? Does it work? And what is the best way to apply it in daily life? I’ve written about this subject before, but new information is now available.

A recent systematic review and meta-analysis published in BMJ Medicine in 2026 by Yu-En Chen and colleagues offers a timely look at intermittent fasting–a diet that focuses on when you eat rather than what you eat. The researchers wanted to know whether timing matters. In other words, if you limit the hours in which you eat, is it better to eat earlier or later in the day?

Intermittent fasting is an eating pattern that alternates between periods of eating and fasting. There are many variations, but one of its most practical forms is time-restricted eating, in which individuals confine their daily food intake to a consistent window–usually between 6 and 12 hours–and fast for the remaining hours of the day. Unlike traditional diets, this method does not necessarily require counting calories or restricting specific foods. The premise is that aligning eating patterns with the body’s internal clock may improve health.

The authors conducted a systematic review of randomized controlled trials–the most rigorous type of clinical evidence–and used a statistical method called network meta-analysis to compare multiple dietary strategies simultaneously. In total, the analysis included 41 randomized controlled trials with 2,287 participants. These studies lasted from four to 48 weeks–a relatively short duration.

The results confirm that time-restricted eating does have measurable benefits. Compared with a usual diet, participants lost an average of about 2.15 kilograms, or roughly 4.7 pounds. This is not dramatic weight loss, but it is consistent and statistically significant. More importantly, the weight loss was accompanied by reductions in fat mass, waist circumference, and body mass index. There was also a small decrease in lean body mass–a reminder that not all weight loss is purely fat.

Beyond weight, several markers of metabolic health improved. Systolic blood pressure dropped by nearly 5 mm Hg–a modest but meaningful improvement. Fasting blood glucose and insulin levels also declined, suggesting improved insulin sensitivity, and triglyceride levels were reduced as well. Interestingly, some of these benefits have been observed even in studies where calorie intake did not change significantly, raising the possibility that timing alone has independent physiological effects.

Up to this point, the findings largely reinforce what many had already suspected: intermittent fasting works, at least to a degree. But the most compelling insight from this analysis lies not in whether people fast, but in when they eat.

The researchers categorized eating windows based on the timing of the last meal: early (before 5 p.m.), mid (between 5 and 7 PM), and late (after 7 p.m.). When these patterns were compared, a clear trend emerged. Early and mid-day eating consistently outperformed late eating across several key outcomes. Participants who finished their meals earlier in the day experienced greater weight loss and better improvements in blood sugar regulation than those who ate later. In direct comparisons, early time-restricted eating led to an additional weight reduction of about 1.15 kilograms compared with late eating, along with significantly lower fasting insulin levels.

The duration of the eating window–whether shorter than eight hours or longer–produced more inconsistent results. While shorter windows sometimes improved certain markers, they did not uniformly outperform longer ones. In contrast, the timing of food intake showed a more reliable and biologically coherent pattern. When timing and duration were considered together, the most favorable outcomes were generally seen in individuals who ate earlier in the day within a relatively limited window.

Why might this be the case? The authors point to the body’s circadian rhythms–its internal 24-hour clock–as a likely explanation. Human metabolism is not constant throughout the day. Glucose tolerance is typically higher in the morning and declines as the day progresses, meaning the body is better equipped to handle carbohydrates earlier rather than later. Insulin secretion and sensitivity follow similar patterns. Eating late in the evening may therefore create a mismatch between food intake and the body’s metabolic readiness, leading to less efficient processing of nutrients.

What emerges from this study is a subtle but important shift in how we think about diet. It is not only the content or quantity of food that matters, but also its placement within the day. Time-restricted eating appears to offer modest but meaningful health benefits, and these benefits are amplified when meals are aligned with the body’s natural rhythms. For those considering intermittent fasting, the evidence suggests that finishing dinner earlier may be just as important as skipping breakfast–or perhaps more so.

EDITOR’S NOTE: Shahar Madjar, MD, MBA, is a urologist and an author. He practices at Schoolcraft Memorial Hospital in Manistique, and in Baraga County Memorial Hospital in L’Anse. Find his books on Amazon or contact him at smadjar@yahoo.com.