When You Eat Breakfast and Dinner Could Affect Your Levels of Body Fat

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Waiting ninety minutes for a brunch table is annoying, but a report in the Journal of Nutritional Science indicates that doing so has the potential to be a promising weight loss technique. Moving back breakfast and dinner time, they show, can have profound effects on the way your body processes meals, akin to the effects of intermittent fasting. Research like this, the authors say, sheds light on new ways of effective dieting. It turns out that what you eat is deeply intertwined with when you eat it.

For the 2018 study, published online in the Journal of Nutritional Science, a team of professors from the University of Surrey’s Faculty of Health and Medical Sciences show that you don’t have to become a disciple of the intermittent fasting dogma to reap the benefits of what they call “time restricted feeding” (TRF).

The team asked ten individuals to delay breakfast by 90 minutes and eat dinner 90 minutes earlier than usual. Results revealed that all those who were able to stick to the schedule reduced their overall body fat by the end of the ten weeks by an average of 1.9 percent.

“This was corroborated by questionnaire responses with 57% of participants noting a reduction in food intake either due to reduced appetite, reduced duration of eating opportunities and/or reduced snacking (particularly in the evening),” the authors wrote.

This results were enough to establish a trend, but not enough to illuminate exactly why body fat decreased. The authors note that it could just be a matter of eating less — the authors describe a “shortened TRF window” — so people had roughly four fewer hours of the day available for snacking when they adhered to the protocol.

An alternative explanation, based on Johnston’s previous research, published in Advances in Nutrition, suggests that the body burns through food at a faster metabolic rate earlier in the day. “One purported mechanism for the health benefits of TRF is that a higher percentage of energy is consumed during a restricted phase of the endogenous circadian cycle,” the team notes in the current study. This means that the time of the day when the individual ate may affect how the body metabolizes the meal.

In the previous study, Johnston and his team wrote that “diet-induced thermogenesis was approximately twice as large in the morning at 0800h compared with in the evening at 2000h,” suggesting that the body burns through food at a faster metabolic rate earlier in the day. Fluctuations in metabolism throughout the day have been a focus of previous research on the benefits of intermittent fasting.

This study does give us one more demonstrable insight into the potential benefits of meal-timing: how easy is it to integrate into life outside of a lab. Fifty seven percent of individuals admitted that they didn’t think they could continue these meal time changes past the end of ten weeks. They also rated the diet a seven out of ten on a scale of difficulty. Seeing as the authors described this group of volunteers as “well-motivated” to follow the diet, these results might not bode well for the rest of us.

“As we have seen with these participants, fasting diets are difficult to follow and may not always be compatible with family and social life,” Johnston said “We therefore need to make sure they are flexible and conducive to real life, as the potential benefits of such diets are clear to see.”

Regardless of how difficult the diet was to follow, the team emphasized that this was only a pilot study. Investigations with more participants and more rigorous designs will be needed to pin down the mechanisms behind these findings.

Emma Betuel is a writer based in NYC. Previously, she covered health and biology for WBUR’s Commonhealth blog and The Borgen Project Magazine