Is Time-Restricted Eating Right for You?

One of the more popular diet trends in recent years is intermittent fasting. Intermittent fasting refers to various patterns of time-dependent eating. This means eating only at certain times. Examples include rotating between eating and fasting (or low calorie) days to time-restricted eating within the same day.

What is Time-Restricted Eating?

Time-restricted eating is a type of intermittent fasting. It’s different from other diet strategies as it focuses on when you eat, not on what you eat. It limits your eating to a set window of time each day. The rest of the day is spent in a state of fasting. Now even without time-restricted eating, we usually have a period of 8-10 hours of fasting while we’re sleeping. But for many of us, our first meal is when we wake up and our last meal/snack just before we go to bed. Time-restricted eating targets a much shorter period of eating between 6 and 12 hours, resulting in a fasting period of 12-18 hours each day.

It also differs from earlier nutrition advice recommending snacks throughout the day. Instead, it’s believed our digestive tract, and related metabolism, need periods of rest from breaking down and metabolizing food. And unlike a lot of other popular diet trends, time-restricted eating is more than just weight loss, but also about metabolic health.

This eating pattern has its origin in how our ancestors ate, going through periods of feast and famine as access to food was limited. It’s only been in the past century that food has been plentiful for a large number of people. Therefore, for thousands of years the human body has got used times of not eating. In essence, we’ve evolved being used to some sort of eating/fasting pattern.

But just because our ancestors ate a certain way, doesn’t mean it’s the best option. Life expectancy has increased remarkably over the past 50 years and improvements to nutrition are one reason why. However, there may be more to intermittent fasting than just being the latest diet fad.

The Benefits of Time-Restricted Eating

As with many diets, people turn to time-restricted eating for weight loss. And why not? It’s often touted as being a diet plan in which you can eat what you want. Whether effective at weight loss is not entirely clear. Small studies in which meals were limited to ten hours or less have demonstrated weight loss in people with obesity, metabolic syndrome and type 2 diabetes.

However, the largest and most robust study found no real effect on weight. In this 12-week study in people who were overweight, eating over eight hours resulted in only a slightly greater amount of weight loss compared to people eating over a 16 hour window. People were allowed to eat what they wanted and there was no attempt to ensure both groups ate the same thing.

While these findings dispel the notion one can eat whatever they want when practising a time-restricted diet, studies control for calories, aren’t any clearer. An eight-week study did find time-restricted eating led to fat loss compared to a control diet group when calories were equal. A larger 12-month study did find time-restricted eating with calorie restriction led to an average weight loss of 17 pounds. However, this was no different from calorie restriction alone.

But the benefits of time-restricted eating are not just limited to weight loss. In men at risk for type 2 diabetes, five weeks of time-restricted eating improved blood sugar metabolism and blood pressure compared to when the same men underwent a control condition eating over a 12 hour period. This occurred despite no apparent changes in weight.

How Does Time-Restricted Eating Work?

Time-restricted eating may work in two ways. The first, it may actually lead to a reduction in hunger and improve the use of fat as an energy source. The second, it aligns periods of eating with the body’s natural internal clock (circadian rhythm).

Your circadian rhythm regulates several processes, which affect how we use or store food we eat. One way is through the hormone melatonin. Melatonin is released by the brain and is best known as the sleep hormone. One of its actions is on the pancreas to get it to stop making insulin. Insulin is responsible for keeping your blood sugar from going too high. When you eat a meal, insulin is released to clear the sugar away into the muscles, liver and other organs for energy use.

At nighttime when melatonin is released, it stops the production of insulin allowing glucose (sugar) to stay in your blood longer. This may seem counter intuitive as we know that excess glucose can lead to type 2 diabetes and heart disease. However, when you’re asleep, you actually need glucose in your blood as you’re not eating for an 8 to 10 hour period. Your body uses that energy to keep it running. Thus, melatonin reduces insulin to ensure you have glucose readily available during the long period of sleep.

When you eat a meal close to bedtime, blood glucose levels remain high as insulin is not available. Over time, this may increase your chances for type 2 diabetes and heart disease through increases in blood glucose and cholesterol. Eating before bedtime can also lead to more disturbing dreams, possibly due to effects of the meal sitting in your stomach being digested.

Is Time-Restricted Eating Right for You?

Plenty of people swear by time-restricted eating as it works for them in maintaining their weight and improving their health. And it’s a diet pattern that can be combined with other plans as well. There’s also biological backing to indicate time-restricted eating may make sense. But to be effective, you likely need to be monitoring what you eat and how much. If your diet is high in highly processed and sugary foods, you’re not doing your body any good regardless of when you eat.

Time-restricted eating may not be for everyone. Some people end up eating more for fear they’ll be hungry later on. You may also be concerned how it will affect your exercise. The studies to date don’t address that directly but suggest it shouldn’t be a problem. And if you’re doing sift work or working late at night, time-restricted eating might not fit your schedule. In the end, the most effective diet plan for you is one that fits into your life.

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This post was originally published on Oct 21, 2020 and updated on Jan 29, 2025.

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