Night owls beware! Study links late sleep habits to belly fat, high blood sugar

Professor Rozanne Kruger from Griffith University’s School of Allied Health, Sport and Social Work studied 287 European and Pacific New Zealand women aged between 18-45 years and assessed if they were morning chronotypes (early bird) or an evening chronotype (night owl).

“Chronotypes influences our preferences for food intake, our behaviours and our metabolism,” Professor Kruger said.

“Both Morning-types and Evening-types consumed similar amounts of food or energy across the day, but it was the timing of eating that was crucial.”

Evening-types consumed less food between 3am and 9:59am but more food between 8pm and 2:59am, while the opposite was true for Morning-types.

Night owls were more likely to consume lower energy and protein intakes in the morning, and ate foods that were high in energy, carbohydrates and fats late at night.

This Evening-type eating and sleeping pattern was associated with greater body fat percentage, belly fat, and higher blood sugar and lipids.

Consuming food at night, when we are supposed to be fasting and sleeping, means we store more food rather than use it, which may increase susceptibility to obesity and cause worse health outcomes.

Women who naturally preferred a later bedtime and wake time were also more likely to have a higher Body Mass Index and Body Fat percentage, poorer lipid profiles, and less favourable indicators of glucose regulation than Morning-types.

“The research highlights that when people eat may be just as important as what they eat,” Professor Kruger said.

“Targeting meal timing, particularly reducing late-night eating, could be an important strategy for improving health amongst people with an evening chronotype.

“It reinforces the role of chrononutrition and the role it plays in obesity and metabolic disease prevention.”

The paper ‘Chronotype and associations with dietary intake, meal timing, body composition, and metabolic biomarkers’ has been published in Frontiers in Nutrition.