What Happens if We Only Take One Meal per Day?

After we ingest food the insulin concentration increases and by doing so, glucose intake and oxidation in peripheral tissues happen.  

Insulin also activates lipoprotein lipase which promotes the storage of dietary fat in adipose tissue. When we fast, the plasma levels of insulin decrease, which results in lipolysis, a shift from glucose to fat oxidation resulting in a state of physiological insulin resistance if the fasting continues. 

From an evolutionary point of view, it may be reasoned that the human body is habituated to a lower meal frequency. Metabolic flexibility is a characteristic of metabolic health, and frequent food intake on the other hand may result in reduced metabolic flexibility, obesity, and type 2 diabetes mellitus. These diseases are associated with modern eating habits and a sedentary lifestyle. 

Nutrition and exercise should be the first in prevention or treatment strategies that need to be implemented in all patients. Intermittent fasting strategies have been used as a way of treatment/prevention strategy, some examples include alternate-day fasting, whole-day fasting, and time-restricted feeding (TRF). 

We are all used to the three-meal food in 24 hours fashion with in-between meal snacking. But what happens if we only take one meal per day or increase timing between meals?

New study on the effects of taking one meal per day 

In a recently published study in the journal Frontiers in Physiology, researchers studied the effect of TFR on metabolism and physical performance in free-living healthy lean individuals. 

The study included 13 healthy individuals. The individuals needed to have a body mass index (BMI) between 20 and 30 kg/m2, and/or fat mass between 12 and 30%, and have training experience in order to be enrolled. Exclusion criteria included the history of cardiovascular disease, diabetes mellitus, eating disorders, mental disorders, smoking, or having another disease that affects metabolism. 

The participants were not allowed to consume alcohol or smoke tobacco during the study. It consisted of 2 study periods of 11 days of TRF. Participants consumed all the calories needed for a stable weight in either three meals per day (3 meals/day, breakfast, lunch, and dinner) or one meal per day (1 meal/day, between 17:00 and 19:00). 

A 2-week wash-out period was included between the study periods. During both study periods, participants were allowed to consume unlimited water, coffee, or tea (without sugar/honey).

The participants used the App form Lifesum for registration and calculation of energy in the daily food intake. They performed physical activity, and performance tests were performed after an overnight fast. They carried an accelerometer at the hip during intervention periods from days 5 to 11. 

The participants performed exercise on an ergometer bike and fat oxidations test were conducted. The participants also performed strength exercises and the strength was measured in exercises such as maximal isokinetic strength in knee extensors and flexors, and jumping exercises (the height in centimeters was measured). 

The researchers found that intended eucaloric meal frequency reduction to one meal per day in the evening, lowered doby-and fat mass and increased fatty acid oxidation during exercise, without impairments of aerobic capacity or strength. Also, they found decreased plasma glucose concentrations during the second half of the day. 

Future studies should evaluate the effects of TRF in participants with reduced metabolic flexibility, such as patients with obesity, metabolic syndrome, or type 2 diabetes to see if the same beneficial effects happen. The researchers also pointed out that their participants were allowed to eat from 7 to 9 pm, and that an early morning meal consumption may yield even larger benefits. 


Emma. C. E. Meessen, et al. Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals. Front. Physiol. 2022. https://doi.org/10.3389/fphys.2021.771944

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Photo by: Francisco Fernandez, M.D.