Time-restricted eating (TRE) has emerged as a novel approach to weight management and health optimisation. Unlike traditional diets that focus on ‘what’ to eat, TRE focuses on ‘when’ to eat.

What is time-restricted eating?

Time-restricted eating is a dietary strategy that limits food intake to a specific number of hours each day. The core principle is synchronising your eating patterns with your body’s circadian rhythms. The circadian rhythm is a natural process that regulates the sleep-wake cycle and repeats roughly every 24 hours. By limiting the eating window, people can potentially improve their metabolic health parameters by aligning nutrient timing with the body’s internal clock.

Example eating windows:

Common frameworks within TRE involve 8-hour eating windows followed by 16-hour fasts (16:8 method), or more extended fasting periods such as a 20-hour fast with a 4-hour eating window (20:4). These are not one-size-fits-all, as the efficacy and comfort of these methods can vary significantly among individuals. You may have heard of the 5:2 diet where calories are reduced for a number of days, rather than a number of hours each day.

How does time-restricted eating work?

During periods of fasting, the body shifts its energy source from glucose to stored fat, promoting fat loss. The focus on time-restricted eating is not about reaching ketosis.

Concurrently, aligning food consumption with daylight cycles optimises your body’s metabolic processes as the endocrine system and metabolic regulation are closely tied to circadian rhythms. TRE works by minimising exposure to food and hunger hormones like ghrelin and potentially correcting insulin resistance by reducing the frequency of insulin release.

What does the science say?

Research into TRE has shown several potential health benefits:

Studies have demonstrated time restricted eating’s potential in reducing the risk of chronic conditions including type 2 diabetes, heart disease, and neurodegenerative diseases. Beyond weight management and metabolic health, TRE has benefits, including:

  1. Improved mental clarity and concentration due to the production of ketone bodies during fasting
  2. Enhanced cellular repair and resilience through the removal of waste material from cells
  3. Potential extension of lifespan and reduction in the risk of age-related diseases

While findings are promising, more extensive human studies are necessary to establish comprehensive guidelines and recommendations

What is autophagy?

One of the pivotal biological processes linked to TRE is autophagy. Autophagy is a cellular mechanism that involves the breakdown and recycling of damaged cell components. Autophagy is triggered during periods of fasting and is akin to your body cleaning up  dysfunctional cellular components and reducing the likelihood of pathological cell growth. This process is crucial for cellular rejuvenation, homeostasis, and defense against various diseases. By promoting autophagy, TRE potentially supports the body’s natural defense mechanisms, contributing to overall health and longevity.

How do I break a fast?

Break your fast with nutrient-dense, low-carb, and real foods to maximise the benefits of TRE. Ideal food choices include:

  1. Lean proteins (chicken, turkey, tofu) to support muscle health.
  2. Healthy fats (avocado, nuts, olive oil) for sustained energy.
  3. Fibre-rich vegetables (leafy greens, cruciferous vegetables) to enhance digestive health.
  4. Berries and other low-glycemic fruits for antioxidative benefits.

As with any dietary approach, consult your healthcare team before starting time restricted eating to ensure it aligns with your health and goals.

Is time restricted eating and intermittent fasting the same thing?

Time-restricted eating (TRE) and intermittent fasting (IF) are terms that are used interchangeably in the media but they refer to slightly different fasting strategies. Time-restricted eating focuses on limiting your daily eating periods to specific windows of time with less emphasis on what you eat and more on when you eat. Most TRE protocols advise a fasting period of 12 to 16 hours, which includes the time you are sleeping, and a feeding window of 8 to 12 hours. The primary goal of TRE is to align eating patterns with the body’s natural circadian rhythm. Intermittent fasting comprises of a broader range of eating patterns that alternate between periods of fasting and eating. These patterns can be daily, as in TRE, or over longer cycles, such as 24-hour fasts once or twice a week, or alternate-day fasting. This approach doesn’t always connect eating patterns to circadian rhythm. Instead, it focuses on longer periods of calorie restriction, which can lead to weight loss and other health benefits due to reduced calorie intake and factors like improved insulin sensitivity. Time-restricted eating is essentially a form of intermittent fasting with a specific focus on circadian biology.

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