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Why fasting between 5.30 pm and 10 am works best to melt belly fat, control blood sugar

A Spanish study finds the optimal 16:8 fasting routine that can be sustained.

The 16:8 method with an eight-hour eating window is effective for fat burn and glucose control. (Representational Image: Pexels)

For some time now, many studies have established the benefits of intermittent fasting, or eating during a specific time period and fasting for others. A new study has now found following an “early” time-restricted pattern — where the last meal is had by 5.30 pm and the next meal not had before 10 am the following day — improves blood sugar regulation and reduces abdominal fat. Of course, it worked well with a Mediterranean diet that study participants had, showing the diet and meal window could be a combined strategy to tackle weight loss.

The Spanish study, published in Nature, involved 200 participants between 30 and 60 years of age with a body mass index (BMI) over 32. They were all on a Mediterranean diet and divided into four time-restricted fasting groups. Researchers found that all fasting groups, regardless of the time-restricted fasting method, had more weight loss — on average 3-4 kg. But those in the early fasting group, who ended their meal by 5.30 pm, had a greater reduction in belly fat and improvement in fasting glucose levels and overnight glucose. This showed that aligning food intake with the body’s natural circadian rhythms is the most beneficial.

According to Dr Parjeet Kaur, Associate Director, Endocrinology and Diabetes, Medanta, Gurugram, early time-restricted feeding (eTRF), where the eating window closes earlier in the day is considered the best for managing blood sugar and body weight. “The specific eight-hour eating window can be adjusted to fit individual lifestyles and preferences as in the study they kept it open between 10 am and 5.30 pm,” she says.

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Why is the 16:8 routine most effective in reducing blood sugar and abdominal fat?

The 16:8 method with an eight-hour eating window is effective for fat burn and glucose control because of a long fasting period. During a fasting state, the body naturally lowers insulin production, which can improve its ability to use insulin effectively when food is consumed during the eating window. So this improves insulin sensitivity and ultimately better blood sugar regulation. With lower insulin levels, the body is more likely to tap into stored glucose, helping to regulate blood sugar levels and manage calories. With a very restricted eating window, the body naturally consumes fewer calories, which can contribute to weight management.

Also See | Here’s what will happen to the body if you do intermittent fasting every other day like Malaika Arora

Does the timing of fasting matter?

The eating window period is important. Early time-restricted feeding (eTRF) has demonstrated greater benefits for metabolic health, including potential anti-ageing effects, compared to eating later in the day.

How does early fasting reduce the amount of abdominal fat?

By limiting your eating window to eight hours, you consume fewer calories. As insulin levels drop, the body looks for stored fat to burn for energy, drawing on visceral fat around the abdomen. Fasting improves the function of the hunger hormone ghrelin and the satiety hormone leptin. So food cravings go down.

Why is more research on time-restricted diets needed?

While time-restricted feeding has shown promising short-term benefits compared to other weight-loss methods, more research is needed to confirm these benefits in the long term. Larger, longer-term studies are required, particularly in diverse populations (like the Indian population) to validate the findings observed primarily in Western populations. This research will help determine the sustainability of the observed benefits.

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