Nutrition Diet: What is time restricted eating called?

November 1, 2025 •

5 min read

According to Johns Hopkins neuroscientist Mark Mattson, our bodies evolved to go without food for long periods, leading to the practice commonly known as intermittent fasting. In this context, what is time restricted eating called is often clarified by explaining its place as a specific method within the broader category of intermittent fasting, offering unique health benefits.

Quick Summary

Time-restricted eating, a specific form of intermittent fasting, confines all caloric intake to a consistent, daily window, typically 8–12 hours. This dietary pattern supports metabolic function by aligning eating with circadian rhythms, which can aid weight management and overall health.

Key Points

Alternate Names: Time-restricted eating (TRE) is a form of intermittent fasting (IF), sometimes also called time-restricted feeding (TRF).
Core Principle: The method involves limiting daily eating to a specific, consistent time window, typically between 6 and 12 hours, followed by a fasting period.
Mechanism: TRE works by promoting metabolic switching and aligning eating patterns with the body's natural circadian rhythms for optimal health.
Health Benefits: Potential benefits include weight loss, improved insulin sensitivity, better blood pressure, and enhanced cellular repair through autophagy.
Popular Methods: Common schedules include 16:8 (8-hour eating window) and 18:6 (6-hour eating window), with early TRE showing specific metabolic advantages.
Starting Out: Beginners should start with a gradual reduction of their eating window, focus on nutrient-dense foods, stay hydrated, and consult a doctor, especially if they have health concerns.
Consistency is Key: Long-term success relies on consistency, but the approach can be easier for many to sustain than continuous calorie-counting.

What is Time-Restricted Eating (TRE)?

Time-restricted eating (TRE) is a dietary approach that focuses on when you eat, rather than what you eat. The core principle is to restrict all calorie intake to a specific daily window, usually between 6 and 12 hours, and to fast for the remaining hours of the day. Unlike other diet plans that strictly limit calories or food groups, TRE offers flexibility in meal content, though most experts still recommend a focus on nutrient-dense whole foods. The popularity of TRE stems from its relative simplicity and the potential for health improvements without meticulous calorie counting.

The Relationship with Intermittent Fasting

Time-restricted eating is a subtype of the broader dietary strategy known as intermittent fasting (IF). While intermittent fasting is an umbrella term that includes various eating patterns, such as the 5:2 diet or alternate-day fasting, TRE is specifically defined by its daily, time-bound feeding and fasting windows. For this reason, TRE is also sometimes referred to as Time-Restricted Feeding (TRF), particularly in preclinical research.

Key Health Mechanisms of TRE

The health benefits of TRE are believed to be rooted in how it interacts with the body's natural circadian rhythms, or internal body clock. By aligning feeding patterns with our biological clock, TRE helps optimize metabolic processes.

Metabolic Switching: After hours without food, the body exhausts its sugar stores and begins burning fat for fuel. This transition is known as metabolic switching, a key benefit of prolonged fasting.
Improved Insulin Sensitivity: Studies show that TRE can increase insulin sensitivity and decrease blood sugar levels, even without significant weight loss. This is particularly beneficial for managing risk factors related to type 2 diabetes.
Weight Management: While TRE can lead to a natural reduction in overall calorie intake by shortening the eating window, some studies suggest its metabolic benefits may be independent of weight loss. Regardless, most research indicates modest reductions in body weight and fat mass, especially in individuals with overweight or obesity.
Cellular Repair: Fasting periods trigger autophagy, the body's natural process of clearing out damaged cells and recycling cellular components, which is associated with anti-aging effects and reduced inflammation.

Popular Types of Time-Restricted Eating

Many different TRE schedules exist, and the right one depends on individual lifestyle and preferences. The consistency of the eating window is often considered more important than the exact duration.

16:8 Method: This is one of the most popular TRE protocols, involving a 16-hour fast and an 8-hour eating window. Many people achieve this by simply skipping breakfast and having their first meal around noon.
18:6 and 20:4 Methods: More restrictive versions of TRE that involve fasting for 18 or 20 hours, with a condensed eating window of 6 or 4 hours, respectively. These are typically for more experienced fasters.
Early TRE (eTRE): Some research indicates that an earlier eating window (e.g., ending by 3 p.m.) may offer additional metabolic benefits, such as improved insulin sensitivity and cardiovascular health, though this may not be feasible for everyone.

Comparison of Time-Restricted Eating Methods


Feature	Time-Restricted Eating (TRE)	5:2 Diet (Intermittent Fasting)	Alternate-Day Fasting (Intermittent Fasting)
Focus	When to eat, confining intake to a daily window (e.g., 16:8).	When to eat, restricting calories on two non-consecutive days.	When to eat, with fasting every other day.
Adherence	Often considered simpler and easier to sustain for many, as it fits into a daily routine.	Some may find calorie restriction on two days difficult, but others prefer it to daily fasting.	Can be the most challenging and extreme method, not ideal for beginners.
Effect on Calories	May lead to a natural, unintentional reduction in daily calorie intake.	Requires conscious calorie counting (500–600) on fasting days.	Involves significant calorie reduction (up to 75% of normal intake) or full fasting on alternate days.
Metabolic Shift	Promotes metabolic switching and alignment with circadian rhythms.	Also induces metabolic changes, but the daily pattern is less consistent.	High degree of metabolic shift due to longer fasting periods, but can be strenuous.

Practical Guide to Starting Time-Restricted Eating

Consult a Healthcare Professional: Before starting any new eating pattern, it is wise to discuss it with a doctor, especially if you have underlying health conditions like diabetes.
Start Gradually: If you typically eat for 13+ hours a day, begin by shortening your window by just an hour or two. Slowly work your way towards a 10 or 8-hour window as your body adapts.
Stay Hydrated: During fasting periods, drink plenty of water, black coffee, or herbal tea to stay hydrated and curb hunger pangs.
Prioritize Nutrition: During your eating window, focus on nutrient-dense foods rich in lean protein, fiber, and healthy fats. This will promote satiety and provide essential nutrients.
Plan Meals: Ensure your meals are spaced out and well-balanced to avoid overeating or relying on junk food within your short window.
Listen to Your Body: Pay attention to how you feel. Some fatigue or irritability is normal initially, but these side effects often decrease with time. Adjust your schedule if needed for sustainability.

Who Should Exercise Caution with TRE?

While TRE is safe for many, certain individuals should avoid or be cautious with the practice without medical supervision:

Children and teenagers under 18.
Pregnant or breastfeeding women.
Individuals with a history of eating disorders.
People with type 1 or type 2 diabetes, especially those taking insulin, due to the risk of hypoglycemia.
Those on medication that needs to be taken with food.
Older adults may be at increased risk of falls or fractures from fluctuating glucose levels.

The Bottom Line: Does TRE Work?

Time-restricted eating offers a structured yet flexible approach to managing your diet that can lead to weight loss and improved metabolic health by working with your body's natural rhythms. Its effectiveness depends on individual adherence and consistency, with many finding it simpler to follow long-term than traditional calorie-restricted diets. While benefits like improved insulin sensitivity and lower blood pressure are often seen, the optimal eating window and long-term impacts are still under investigation. For many, the simplicity of 'watching the clock' instead of counting calories is a powerful tool for lasting lifestyle change.

For further reading on the science behind TRE, the Salk Institute has conducted significant research on the topic.

Frequently Asked Questions

Time-restricted eating (TRE) is a specific type of intermittent fasting (IF). While IF is a broad term for various eating-fasting schedules, TRE focuses specifically on confining all calorie intake to a consistent, daily window, like 8 hours, and fasting for the remaining 16 hours.

The 16:8 diet is one of the most popular forms of time-restricted eating. It involves fasting for 16 hours each day and consuming all your food within an 8-hour window. A common approach is skipping breakfast and eating between noon and 8 p.m..

During the fasting period, your body burns through its glycogen (sugar) stores. After these stores are depleted, the body shifts to burning stored fat for energy, a process called metabolic switching. This helps with weight loss and can improve metabolic health.

No, one of the key benefits of time-restricted eating is that you don't have to count calories. By simply restricting the time you eat, many people naturally consume fewer calories without consciously monitoring them.

Yes, you can drink zero-calorie beverages such as black coffee, plain tea, and water during your fasting window. Adding sugar, milk, or cream would break the fast by adding calories.

No, it is not for everyone. Individuals who are pregnant, breastfeeding, under 18, have a history of eating disorders, or are on medication that requires food should be cautious and consult a doctor. People with diabetes should also seek medical advice before starting.

Some common initial side effects include hunger, irritability, headaches, and fatigue as your body adjusts to the new eating pattern. These symptoms often subside within a few weeks.