By Dr. Frank Sabatino

The sublime dance of life and health is choreographed by a remarkable array of rhythms and patterns around and within us. As the earth spins on its axis over a 24 hour period, a circadian rhythm synchronized to the daily cycle of day light and darkness influences our important cycle of sleep and wakefulness, as well as a variety of biological activities including  metabolism and energy production, body temperature, the release of hormones and neurotransmitters from the endocrine and nervous systems, and even feelings of appetite/hunger. This daily rhythm is driven by a cluster of nerve cells ( suprachiasmatic nucleus) in a part of the brain called the hypothalamus that function as your internal clock. 

While health and the timing of sleep and wakefulness are closely tied to this circadian directive for all animals, humans have adopted social conventions and lifestyle aberrations that disconnect them from their basic circadian rhythm with things that include night shift work, travel across time zones, excessive consumption of caffeine, alcohol, addictive sleep medications, chronic stress, and the timing and  frequency of food consumption. However, the more that you maintain healthy lifestyle habits that connect and align you with the natural  rhythm of your light- dark (wake/sleep) cycle, the more you enhance your quality of life and health. 

As a result,  there has been a burgeoning interest in  chrononutrition focused on the timing of your food intake in relation to your circadian clock. This has fostered a body of evidence suggesting that ‘when’ you eat, as well as ‘what’ you eat, may play a significant role in weight management and healthy metabolic function. The timing of eating can synchronize different body parts related to food digestion, absorption, and metabolism, affecting the mobilization, utilization, and accumulation of body fat, and play a significant role in promoting or preventing obesity and weight gain. (1)

Numerous studies have revealed associations and correlations between the timing of food intake and changes in weight and metabolism.  In a 12 week study of people on a weight loss regimen of 1400 calories per day, subjects consuming 700 calories for breakfast and 300 calories for dinner lost significantly more weight that those eating the reduced calories for breakfast and increased calories for dinner. (2) The obesity generating effect of eating more food later in the day has been a consistent observation. In obese subjects of similar ages, calorie density intake, exercise energy expenditure, and sleep duration, consuming large lunches in the late vs. early afternoon resulted in a significant reduction in weight loss. (3) Late eaters who consumed lunch after 4:30 were typically late night eaters that stayed up late, got up later in the morning and felt that they performed better mentally in late afternoon and evening. However, they typically manifested metabolic disturbances of decreased glucose tolerance with compromised blood sugar control, decreased resting energy expenditure, and decreased carbohydrate oxidation/digestion compared to early eaters.

It is also important to realize the significant role of  the hormone melatonin in the light-dark cycle and the impact of food timing. Melatonin plays a central role in circadian rhythm as the main signal of biological night. It is the chemical expression of darkness for the brain. Higher melatonin levels usually peak close to bedtime and tend to cause glucose intolerance and higher blood sugar levels. The closer late night and night eating are to bedtime, and the elevated levels of melatonin, the more compromised is the function of insulin ( insulin resistance), and the higher blood sugar and insulin levels are during sleep. (4) This is consistent with evidence showing a robust association of late night eating with high blood sugar, and the significant increase in insulin resistance  that occurs when your highest calorie intake occurs during dinner compared to breakfast. (2) International studies associated late dinner or eating late with an increased risk of obesity, an imbalance of cholesterol and triglycerides in the blood, hyperglycemia, and metabolic syndrome (high blood pressure, excess waist size/fat, high blood sugar and cholesterol) that may increase the risk of heart disease, stroke, and type 2-diabetes. (5)(6)(7). These metabolic changes may have direct effects on the increase in body fat. People consuming 50% of their calories eight hours before biological night had a significant decrease in body mass index and body fat percentage compared  to those consuming 50% of their calories 4 hours before biological night. (8) 

A glaring example of the negative effects of night eating is seen in night shift workers who typically have a higher risk of obesity and type 2 diabetes. These workers often have abnormal levels of hormones involved in appetite regulation, and typically experience increased craving for high calorie dense foods , including high-fat and high refined sugar processed foods. (9)(10)(11) When considering food intake relative to the sleep-wake cycle, eating consistently at night, within 2 hours of sleep, correlates to a 5-fold increase in  the probability of being obese, while eating high calories at breakfast, within 2 hours of waking up,  is associated with a 50% decrease in the probability of being obese. (1)

Intermittent fasting is a time restricted pattern of eating that can help you get back in touch with the healthy, natural, diurnal rhythm of day and night to adjust the timing of your food intake for best advantage. I typically recommend a 14:10 cycle of intermittent fasting ( eating between the hours of 8:30 or 9 AM and  5-6:30 or 7 PM,  and fasting 14 hours through the evening and night) that I employ in my own health retreats and is comfortable for most people to do. This will urge you to avoid eating at night when you should be winding down and preparing for sleep. This reduction in food intake at night close to bedtime can help improve hormone function, reverse insulin resistance, improve fat metabolism and lower weight and body fat. 

Consider the following strategies to ensure healthy weight and metabolism

• Maintain a whole-food plant-exclusive diet without added salt, oil, and sugar.
• Eat a substantial healthy breakfast with more calories for breakfast, lunch and throughout earlier times of day.
• Eat a lighter dinner earlier, preferably in the window of time between 5-7 PM
• Make dinner the last meal of the day and avoid late night snacking and eating.
• Have your dinner, the last meal of the day, at least 2-3 hours before bedtime.

References

1. Lopez-Minguez  J, et al. Timing of breakfast, lunch, and dinner, effect on obesity and metabolic risk. Nutrients 2019;11(11):2624.

2. Jakubowicz D, et al. High caloric intake at breakfast vs, dinner differentially influences weight loss of overweight and obese women, Obesity 2013;21:2504-2512.

3. Garaulet M, and Gomez-Abellon P. Timing of food intake and obesity: a novel association. Physiol Behav. 2014;134:44-50.

4. Morris CJ, et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proc Natl Acad Sci. USA, 2015;112:E2225-E2234.

5. Xiao Q, et al. Meal timing and obesity: interactions with macronutrient intake and chronotype. Int J Obes. 2019;43:1701-1711.

6. Yoshida J, et al. Association of night eating habits with metabolic syndrome and its components: a longitudinal study. BMC Public Health 2018;18:1366.

7. Chen HJ, et al. Energy intake at different times of day: its association with elevated total and LDL cholesterol levels. Nutr Metab Cardiovasc Dis. 2019;29:390-397.

8. Mchill AW, et al. Later circadian timing of food intake is associated with increased body fat. Am J Clin Nutr. 2017;106:1213-1219.

9. Pan A, et al. Rotating night shift work and risk of type 2 diabetes: two prospective cohort studies in women. PLoS Med. 2011;8:e1001141.

10. Cain SW, et al. Enhanced preference for high fat-foods following a simulated night shift, Scand J Work Environ. Health 2015;41:288-293.

11. Bonnell EK, et al. Influences on dietary choice during day versus night shift in shift workers: a mixed methods study. Nutrients 2017;9:193.