Eating foods later in the day can predispose to obesity and metabolic syndrome through several potential mechanisms. Since sleep decreases metabolic rate, eating close to bedtime may reduce the rate of oxidation of ingested nutrients and shift energy source preference for the body, thus extra energy would be more likely stored as fat tissue.

 

    One study examined whether eating a late dinner may alter metabolism during sleep that promotes obesity (1). The study participants were 20 healthy volunteers (10 male, 10 female), age 26.0 ± 0.6 years, body mass index 23.2 ± 0.7 kg/m2, accustomed to a bedtime between 22:00 and 01:00. They were randomized in the crossover trial of late dinner (22:00) vs routine dinner (18:00), with a fixed sleep period (23:00-07:00).

 

    An isocaloric macronutrient diet was administered on both visits. Dinner (35% daily kcal, 50% carbohydrate, 35% fat) with an oral lipid tracer ([2H31] palmitate, 15 mg/kg) was given at 18:00 with routine dinner and 22:00 with late dinner. The oral lipid tracer taken with the dinner would quantify exogenous fatty acid oxidation calculated by hourly assessment of deuterium incorporation into plasma 2H2O using isotope ratio mass spectrometry.

 

    Measurements included nocturnal and next-morning hourly plasma glucose, insulin, triglycerides, free fatty acids, cortisol, dietary fatty acid oxidation, and overnight polysomnography.

 

    Late dinner caused a 4-hour shift in the postprandial period, overlapping with the sleep phase. Compared with the routine dinner, the postprandial period following late dinner was characterized by higher glucose, a triglyceride peak delay, and lower free fatty acids and dietary fatty acid oxidation. Late dinner did not affect sleep architecture but increased plasma cortisol. These metabolic changes were most pronounced in habitual earlier sleepers determined by actigraphy monitoring. Exogenous fatty acid metabolism as measured by using [2H31] palmitate ingested with late dinner showed approximately 10% less oxidation by the following morning compared to regular dinner.

 

    This study showed that late dinner induced nocturnal glucose intolerance, and reduced fatty acid oxidation and metabolism, particularly in earlier sleepers. These effects might promote obesity if they recur chronically (1).

 

    Not only the dinner time but also the size of the dinner may impact bodyweight. One study compared the effect of a weight loss diet with either high caloric intake at breakfast to an isocaloric diet with high caloric intake at dinner (2).

 

   Overweight and obese women (BMI 32.4 ± 1.8 kg/m(2) ) with metabolic syndrome were randomized into two isocaloric (~1400 kcal) weight loss groups, a breakfast  (700 kcal breakfast, 500 kcal lunch, 200 kcal dinner) or dinner group (200 kcal breakfast, 500 kcal lunch, 700 kcal dinner) for 12 weeks.

 

    Bodyweight decreased significantly (p < 0.0001) in both the breakfast and dinner groups over 12 weeks. However, compared with the dinner group, the breakfast group showed a 2.5-fold greater weight loss (28.7 ± 1.4 vs. 23.6 ± 1.5 kg, respectively) (p < 0.0001). As a result, the BMI was significantly different between the groups (p < 0.0001), with a 10% reduction in the breakfast group and only a 5% reduction in the dinner group. Participants assigned to the breakfast plan also showed a greater reduction in waist circumference than participants assigned to the dinner plan, both at 6 and 12-week follow-ups (28.5 ± 1.9 vs. 23.9 ± 1.4 cm, respectively) (p < 0.0001).

 

    Although fasting glucose, insulin, and ghrelin were reduced in both groups, fasting glucose, insulin, and HOMA-IR decreased significantly to a greater extent in the breakfast group. Mean triglyceride levels decreased by 33.6% in the breakfast group but increased by 14.6% in the dinner group. Oral glucose tolerance test led to a greater decrease of glucose and insulin in the breakfast group. In response to meal challenges, the overall daily glucose, insulin, ghrelin, and mean hunger scores were significantly lower, whereas mean satiety scores were significantly higher in the breakfast group.

 

    A high-calorie breakfast with reduced intake at dinner and avoiding late dinner time are beneficial strategies for the management of obesity and metabolic syndrome.

 

Reference list:

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1. Gu, C., Brereton, N., Schweitzer, A., Cotter, M., Duan, D., Børsheim, E., … Jun, J. C. (2020). Metabolic Effects of Late Dinner in Healthy Volunteers – A Randomized Crossover Clinical Trial. The Journal of Clinical Endocrinology & Metabolism.

2. Jakubowicz, D., Barnea, M., Wainstein, J., & Froy, O. (2013). High Caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity, 21(12), 2504–2512.