written by Lauren Elizabeth April 17, 2021

Is “when” just as important as “what” to eat and “how” much to eat?

When it comes to weight loss strategies, we are no stranger to reducing calories and choosing less processed and more nutrient-dense foods. Have you ever thought about the timing of meals as a weight-loss strategy? A common weight loss strategy is to not eat after 7 PM. Phrases such as “breakfast is the most important meal of the day” and  “eat breakfast like a king, lunch like a prince, and dinner like a pauper” are used to emphasize that weight-loss strategy.  I decided to research for any truth behind these claims. Let me say there was an abundance of scientific research on the topic. To put into perspective, just one of the review studies I came across reviewed over 35 studies and approximately 447,352 subjects and the impact of meal timing on obesity and metabolic risk.1 What does this mean for you, my readers? Well, let’s dig in and find out!

Our circadian rhythm is an internal process that regulates our sleep-wake cycle. But it is also intricately tied to our food habits and eating patterns. Unusual eating patterns, such as eating late, may disrupt this internal clock and lead to unhealthy consequences. Our meal timing may influence food digestion, absorption, and metabolism. Evidence has shown that meal timing may be an emerging factor in weight loss therapies.1 The night phase of the circadian rhythm is identified by the onset of melatonin under dim light (DLMO). Depending on an individual’s chronotype, it will determine when the melatonin onset occurs. To assess your DLMO would require invasive and repetitive blood collections to measure melatonin concentrations over time. To better estimate, your circadian time of food intake, consider your food intake relative to your sleep-wake cycle. This approach to food consumption showed that individuals with higher energy intake two hours before bedtime increased five times their probability of being obese. This field of nutrition has been named “Chrononutrition” and has opened a door for further research. Below is a summary of the key findings from the study review:1

  • Eating in misalignment with our internal clock is associated with an increased risk for diabetes, obesity, dyslipidemia, hyperglycemia, and metabolic syndrome.
  • Late eating expressed a blunted cortisol response compared to early eating. This type of cortisol response, similar to a chronic stress response, is associated with a higher BMI and a precursor to several disorders.
  • Subjects that consumed approximately 50% of their food intake, caloric midpoint, eight hours before DLMO were significantly leaner. Those who had a late caloric midpoint, four hours before DLMO, had a higher BMI and were overweight/obese.
  • Consuming your main meal late (after 3 PM) predicted difficulty in weight loss.
  • Subjects assigned to a small breakfast and a large dinner lost significantly less weight than those set to a large breakfast and a small dinner.
  • Meal timing may affect other circadian-related processes that predict weight loss.
  • Weight loss effectiveness, adherence, and food timing are associated with a particular gene.
  • Late eating decreased glucose tolerance/ greater insulin resistance – resulting in higher concentrations of blood glucose leading to diabetes, resting energy expenditure – lower metabolism, and carbohydrate oxidation – the ability of your body to utilize glucose for fuel.
  • Skipping breakfast is causally linked to obesity.
  • Morning chronotypes consuming most calories in the morning, two hours after waking, decreases their likelihood of being obese by 50%.

In conclusion, it is recommended to consume a majority of your calories earlier in the day and refrain from eating 2-4 hours prior to bedtime. To determine your “chronotype” review your sleep-wake cycle and adjust your eating pattern according to the bullets points listed above.

  1. Lopez-Minguez J, Gómez-Abellán P, Garaulet M. Timing of Breakfast, Lunch, and Dinner. Effects on Obesity and Metabolic Risk. Nutrients. 2019;11(11):2624. Published 2019 Nov 1. doi:10.3390/nu11112624

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