How Late Night Eating Affects Weight Loss

Mounting evidence suggests that eating late at night could affect the ability to lose weight and have an impact on your health, but why so? We explore the research.

Published: Tuesday 13 September 2022

Eating late Weight Loss

When it comes to losing weight, most of the focus tends to be on what you’re eating. The common advice is to avoid sugary and fatty foods, drink more water, and eat more vegetables; however, research shows that your ability to lose weight can be influenced by the time you eat too. You may have heard that eating late can lead to weight gain - but what is the scientific evidence behind this, how does it affect our ability to lose weight and what time is best to eat if you’re trying to lose weight?

What is our circadian rhythm?

Circadian rhythm is the name given to the collective physical, mental and behavioural processes occurring within our bodies during a 24 hour cycle. These changes occur in response to stimuli from our environment, particularly light intensity which is responsible for regulating our sleep cycle. Circadian rhythms have contributed to the process of human evolution by allowing us to adapt to external stimuli such as temperature, physical activity and food availability [1].

An important physiological process also controlled by circadian rhythms is the body’s metabolism - a crucial, but complex chemical reaction in which our bodies convert food into energy by a process known as respiration. Since metabolism is linked to circadian rhythm, anything that influences your circadian rhythm can affect your weight loss results.

What effect does eating late have on weight loss?

Eating late is the norm across many cultures, but a collection of recent studies now indicate that the practice of eating late could affect how effectively your body metabolises food. Evidence has shown that eating late disrupts the circadian rhythm and body clock, which has a knock-on effect on hormone regulation and organ function, especially when it comes to digesting food [2].

This was highlighted in a 2020 study that found that eating a late dinner led to a 4 hour shift in the postprandial period (the phase after digestion in which nutrients are metabolised), causing it to overlap with the sleep phase of the body [3]. Researchers found that because of this shift in the postprandial phase, there was an increased level of glucose in the body whilst sleeping and a decrease in the breakdown of fatty acids. If eating late became a regular habit, the increased build up of sugars and fatty acids could contribute to an increase in weight. In addition, researchers of the study also found that the effects of the postprandial shift also led to an increase in plasma cortisol, indicating an increase in stress.

Researchers believe that by eating late at night (1-2 hours before sleeping) our bodies are not given an adequate amount of time to digest the food. This means that our bodies are still digesting food whilst we are sleeping, thus having an impact on the quality of our sleep. Research has suggested that a lack of good quality sleep may cause an increase in appetite due to an effect on neurotransmitter regulation. In addition, some studies have shown that sleep deprivation can cause individuals to choose foods high in carbohydrates and calories, which increases the chance of putting on weight [4].

What are the best times to eat for effective weight loss results?

In a study earlier this year, researchers found that early time-restricted eating (eTRE) was more effective for losing weight compared to eating over a period of 12 hours or more [5]. In the study, all participants were given the same meal plan that contained the same number of calories, but with different meal timings. Participants restricted to eating between 7am and 3pm lost an additional 214 calories per day (2.7kg overall weight loss) compared to participants who ate with no time restrictions. Furthermore, results also indicated that participants who were in the group with eating restrictions also experienced a reduction in diastolic blood pressure and an improvement in mood.

Researchers acknowledged that 3pm is too early in the day to stop eating, but emphasised that giving your body an adequate amount of time (around 4 hours) between your final meal of the day and the time you go to sleep will still have a positive effect if you are looking to lose weight.

What alternative weight loss treatments are available?

An alternative way of losing weight is through the use of a weight loss treatment. Here at Pharmica, we offer a variety of treatments, including:

  • Orlistat (120mg): a weight loss aid for adults with a BMI over 30, or those with a BMI over 28 with an associated risk of certain health conditions (diabetes, hypertension, heart disease or high cholesterol).
  • Xenical (120mg): a branded version of Orlistat, used to assist weight loss in adults with a BMI over 30, or those with a BMI over 28 with an associated risk of certain health conditions (diabetes, hypertension, heart disease or high cholesterol).
  • Orlos (60mg): an alternative weight loss aid for adults with a BMI of 28 or above.
  • Alli (60mg): a weight loss aid for adults with a BMI of 28 or higher.

These treatments are most effective when used in conjunction with making lifestyle changes, such as the foods you’re eating and the amount of exercise you do. Browse our weight loss articles for more ways on how to get the most out of your weight loss treatments.


There have been a variety of studies that have investigated the effect eating late at night has on weight loss and have found that there is strong evidence to suggest that repeatedly eating late disrupts the circadian rhythm, which leads to an increased risk of obesity. If you are looking to lose weight, research highlights that you should leave an adequate amount of time between your final meal and the time you go to sleep in order to give your body enough time to digest meals without the digestive process overlapping with your sleep schedule.

Amber Mitchell-Hanna

Written by: Amber Mitchell-Hanna

Pharmica Medical Writer

Amber is an experienced writer and content specialist, graduating from De Montfort University with an LLB & an MA in Investigative Journalism.

She particularly enjoys creating informative health content, debunking medical misconceptions, and championing inclusion and diversity.

Find out more about how we ensure the accuracy of our content with our content guidelines.

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