Eating out of sync with normal mealtimes, namely late at night, is associated with an increased risk of obesity, hyperglycemia, dyslipidemia, insulin sensitivity, and metabolic syndrome, according to the results of a new study published in the American Journal of Clinical Nutrition.1

The associations between late eating and higher concentrations of triglycerides and lower insulin sensitivity were independent of BMI, noted lead author Hassan S. Dashti, PhD, of the Center for Genomic Medicine at Massachusetts General Hospital in Boston. Understanding why a person is eating later at night may be useful in the development of “future interventions aimed at advancing the timing of food intake.”

“Most nutrition research to date has focused exclusively on what to eat, and not when to eat,” wrote Leah E. Cahill, RD/PDt, PhD, R. Howard Webster Research Chair in Medicine, Department of Medicine, Dalhousie University in Halifax, Nova Scotia, in an accompanying editorial.2  

Although late eating is a hot topic in nutrition, no standard terminology, methodology, or definitions exist. There are many terms used for late eating, noted Dr Cahill, including  “eating patterns,” “chrono-nutrition,” “food timing,” “eating regularity,” “eating habits,” and “meal timing and frequency,” adding to the confusion.


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The investigators sought to understand how food timing is associated with obesity and cardiometabolic risk factors. Previous studies by the authors and others have shown that “acute circadian misalignment in the form of jet lag, shift work, and late meal timing, adversely impacts energy balance and glycemic control.”3,4 However, when it comes to food timing, “there remains a paucity of consistent evidence regarding its relation to obesity, cardiometabolic risk factors, and weight-loss success,” the investigators said.

Study Design

A total of 3362 overweight or obese adults (BMI: 31.05 (5.58) kg/m2) were enrolled in a weight loss program in Spain. Patients were excluded if they were taking weight-loss medications, undergoing treatment with anxiolytic or antidepressant drugs, or had comorbid health condition (eg, diabetes, heart disease), or a history of eating disorders.

Prior to the start of the study, cardiometabolic and satiety hormonal profiles were measured from fasting blood samples; thereafter, weight loss was measured weekly and participants completed a survey on barriers to weight loss at week 5 of the 19-week program. All the participants followed a standardized weight-loss program based on the Mediterranean diet and attended a weekly 1-hour small group (n=10) therapy session.

Defining Early vs Late Eating

The investigators developed a new method of defining early and late eating, noted Dr Cahill. Participants were dichotomized by the population median into early (midpoint before 14:54) and late (midpoint after 14:54) eaters. The groups were “easy to compute from a 24-h food recall, it is logical in relation to diurnal and circadian rhythms, and it effectively captured differences between later and earlier eaters,” Dr. Cahill said.

The average recorded meal times were 8:31 (breakfast), 14:36 (lunch), and 21:21 (dinner); with lunch comprising the highest relative energy density (39%), followed by dinner (28%) and breakfast (18%). As expected, late eaters reported having all meals at a later time than early eaters, with the largest difference (>1 hour) for breakfast followed by dinner (>30 minutes). These meal times may reflect the later meal times of Europeans compared with Americans.

Late Eating Linked to Higher Triglycerides, Lower Insulin Sensitivity

At the start of the program, no differences were observed in energy intake or physical activity levels between early and late eaters. However, late eaters had higher BMI, higher concentrations of triglycerides, and lower insulin sensitivity compared with early eaters (all P <.05) prior to intervention. In addition, late eaters had higher concentrations of the satiety hormone leptin in the morning (P =.001).

After the start of the program, late eaters had an average 80 g lower weekly rate of weight loss [early, 585 (667) g/wk; late, 505 (467) g/wk; P =.008], higher odds of having weight-loss barriers [odds ratio [OR], 1.22; 95% CI, 1.03-1.46; P =.025], and lower odds of motivation for weight loss [OR, 0.81; 95% CI, 0.66-0.99; P =.044] compared with early eaters.

Late Eaters Lose Less Weight

Among 2119 participants who completed the weight-loss program, the researchers found that late eaters had lower success and a lower weekly average rate of weight loss compared with early eaters. Late eaters were also found to have an evening chronotype (MEQ score), an important determinant of food timing, and lower morning appetite than early eaters.  

“We observed that late eating was associated with several obesogenic behaviors [stress-related eating and eating at night while watching TV] that may hinder weight-loss success,” the investigators said.

“The biological mechanism linking late eating to obesity is likely multifactorial,” noted Dr Cahill. “More eating timing research studies, such as the study conducted by Dashti et al are required to determine whether eating timing is an intervention target point for a healthier lifestyle for the general population and for better risk management for patients.”

Disclosure: 1 author has declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

References

1. Dashti HS, Gómez-Abellán P, Qian J, et al. Late eating is associated with cardiometabolic risk traits, obesogenic behaviors, and impaired weight loss.  Am J Clin Nutr. 2021;113(1):154-161. doi:10.1093/ajcn/nqaa264

2. Cahill LE. About time: eating timing is a complex risk factor for obesity. Am J Clin Nutri. 2021;131(1):5-6. doi:10.1093/ajcn/nqaa329

3. McHill AW, Phillips AJ, Czeisler CA, et al. Later circadian timing of food intake is associated with increased body fat.  Am J Clin Nutr. 2017;106(5):1213-1219.  doi: 10.3945/ajcn.117.161588

4. Garaulet M, Gómez-Abellán P. Timing of food intake and obesity: a novel association. Physiol Behav. 2014;134:44-50.  doi:10.1016/j.physbeh.2014.01.001