In this article, learn more about what it means to eat one meal per day, and find out more about the possible benefits and risks.
Is Eating One Meal a Day a Safe and Effective Way to Lose Weight?
Eating one meal a day is a practice that many people swear by to lose weight and improve overall health. The one-meal-per-day diet is also referred to as OMAD.
Although the content and timing of the meal will vary based on personal preference, people following an OMAD diet typically restrict their calorie intake to a single meal or a short window of time.
The potential health benefits of OMAD are primarily related to fasting — restricting calorie intake during a set time period — and calorie restriction in general.
There are many types of intermittent fasting practices and multiple ways to implement OMAD.
Examples include having just one meal and fasting for the rest of the day or having one meal and eating limited amounts of food during fasting periods.
This type of diet creates a calorie deficit, which can lead to weight loss.
Other health benefits related to fasting include the potential to reduce heart disease risk factors, decrease blood sugar, and reduce inflammation ( 1 ).
However, compared to other fasting regimens, such as the 16/8 method, which involves 8-hour eating windows and 16-hour fasting windows, eating just one meal per day is one of the most extreme methods of intermittent fasting.
A few popular diets encourage eating one meal per day. For example, when following the Warrior Diet, a person eats a single meal a day, cycling between long periods of fasting with short periods of energy consumption.
Most people following OMAD choose to only consume dinner, although others choose breakfast or lunch as their one meal. Some versions of this eating pattern allow a snack or two in addition to the one meal.
However, some OMAD enthusiasts don’t consume anything containing calories during their fasting window and only consume calories during their chosen meal, which typically lasts an hour or so.
In order to lose weight, you must create an energy deficit.
You can do this by either increasing the number of calories you burn or reducing your calorie intake. Calorie restriction, no matter how you achieve it, will lead to fat loss.
People using the OMAD method are likely to lose weight simply because they’re taking in fewer overall calories than they normally would during a regular pattern of eating.
For example, a study in healthy adults found that restricting calorie intake to a 4-hour time period in the evening led to significantly greater body fat loss than when eating three separate meals throughout the day ( 2 ).
Research has also shown that intermittent fasting, including extended fasting periods like OMAD, is likely to result in weight loss.
However, it doesn’t seem to be any more effective than traditional methods of calorie restriction, such as reducing calorie intake at each meal ( 3 ).
An analysis that included 50,660 people showed that those who consumed 1 or 2 meals per day had a yearly reduction in body mass index (BMI) compared to those who consumed 3 meals per day.
The study also showed that an overnight fast of 18 or more hours was associated with decreased body weight, compared to shorter fasting windows ( 4 ).
However, these weight loss benefits are related to intermittent fasting in general, and not just the OMAD.
Plus, extreme methods of fasting, such as OMAD, may have side effects that people need to consider, such as increased hunger and problematic metabolic changes ( 5 ).
In addition to weight loss, research has linked fasting to a number of other health benefits. For example, fasting may help reduce blood sugar and certain heart disease risk factors, including LDL “bad” cholesterol ( 6 , 7 ).
Fasting has also been associated with reduction in markers of inflammation, including C-reactive protein ( 6 ).
Additionally, fasting may offer unique benefits for the health of the nervous system. It may slow neurodegeneration and promote longevity, according to animal research ( 8 , 9 ).
However, although these potential benefits are promising, it’s important to note that these benefits are associated with fasting in general and not OMAD specifically.
In fact, some research shows that the OMAD pattern may be more detrimental to health than other, less restrictive fasting methods ( 2 , 10 , 11 ).
Although research has associated fasting and calorie restriction with a variety of health benefits, some evidence suggests that restricting too much — which can include only consuming one meal a day — may do more harm than good.
For example, studies suggest that this extreme restriction may lead to increased total and LDL “bad” cholesterol and higher blood pressure levels compared to normal eating patterns or less extreme fasting methods ( 2 ).
Other studies have shown that eating one meal per day may increase fasting blood sugar levels, delay the body’s response to insulin, and increase levels of the appetite-stimulating hormone ghrelin, compared to eating 3 meals per day.
This can lead to extreme hunger ( 10 ).
What’s more, restricting calories to one meal a day may increase the chances of hypoglycemia, or low blood sugar, especially in those with type 2 diabetes ( 11 ).
In addition to these potential adverse effects, eating one meal a day can lead to symptoms including ( 12 ):
The OMAD diet is also not appropriate for many groups of people, including those who are pregnant or breastfeeding, children and teens, older adults, and people with eating disorders.
Limiting intake to one meal per day can also lead to disordered eating tendencies, impact a person’s social life, and be extremely difficult for most people to stick to.
What’s more, it can be very difficult to take in enough nutrients in one meal. This can lead to nutrient deficiencies, which can negatively affect your health and can lead to serious risks.
Lastly, some people following the OMAD dietary pattern will binge on highly processed, calorie-dense foods, like fast food, pizza, doughnuts, and ice cream, during their one meal.
While these foods can fit into a balanced lifestyle, exclusively eating foods high in added sugar and other unhealthful ingredients will negatively affect your health in the long run.
Overall, although there are benefits related to fasting and calorie restriction, research has shown that consuming 2 or 3 meals per day is likely a better option for overall health than eating one meal a day ( 5 ).
Should I eat just one meal a day?
The one-meal-a-day diet is an eating plan that claims to help people lose weight through intermittent fasting.
When following this diet, a person will eat only one meal a day. This is usually dinner. They do not consume any other calories during the day.
Although this diet plan may offer a fast weight loss solution for some people, the risks may outweigh the benefits.
In this article, learn more about what it means to eat one meal per day, and find out more about the possible benefits and risks.
The one-meal-a-day diet is a weight loss plan in which a person eats only one meal per day. On this plan, they will not eat or drink anything containing calories for most of the day.
It is a type of intermittent fasting. It alternates long periods without eating or drinking anything containing calories with short time windows for eating.
The diet utilizes a type of intermittent fasting called 23:1. This means that a person spends 23 hours of the day fasting, leaving just 1 hour per day to consume calories.
Most people who follow this diet eat their meal at dinner time, then fast again until the following evening. However, some research suggests that eating breakfast may aid glucose control later in the day and reduce the risk of type 2 diabetes .
Other research contradicts these conclusions, suggesting that skipping breakfast may actually be a beneficial strategy for some people in managing overall calorie consumption.
For those who intend to eat breakfast and lose weight, learn which breakfast foods are best in this article.
What should a person eat on this diet?
There are several versions of the one-meal-a-day diet. Some suggest eating healthful, nutrient-rich foods, but most allow people to eat anything they want during their single meal.
People who follow the one-meal-a-day diet believe that it offers numerous benefits, such as the fact that:
- People can lose weight rapidly.
- The diet is easy to follow because there is no need to count calories.
- No food is off-limits.
Learn more about the possible benefits of intermittent fasting here.
However, there is little evidence to support the notion that the one-meal-a-day can aid weight loss.
One study in a review suggests that intermittent fasting may help people lose weight, though the authors also warn of multiple risks, such as rebound body fat increases.
Only one of the included studies focused on the one-meal-a-day pattern. Participants in this study ate their daily calories during a 4-hour window in the evening. Many saw improvements in fat mass and body weight, while others had increased cholesterol and blood pressure.
Other research , meanwhile, has concluded that alternate-day fasting was no more effective than a calorie-restriction diet in terms of weight loss, keeping weight off, cardiovascular risk, or being able to stick with the diet.
Other studies of intermittent fasting have found the following:
- Short-term fasting, in which people eat during a 4–8 hour window, may lower blood sugar levels and reduce weight in people with type 2 diabetes.
- Fasting 15 hours per day for a month may benefit a person’s overall health and, in people with obesity, boost the body cells’ ability to resist disease.
- Time-restricted feeding, or eating within an 8-hour or shorter window, turns on autophagy, which is a process that the body uses to clean up damaged material, according to a 2017 study . This may prove to be a valuable strategy in preventing and treating many age-related chronic conditions.
Many of these studies did not specifically address the one-meal-a-day option, however.
Intermittent fasting has become increasingly popular with people looking to lose weight or improve their overall health. Learn more about it here.
There has been little research into the effects of fasting for 23 hours per day. As an extreme diet plan, however, there may be risks.
For example, on a daily basis, a person may:
- feel very hungry
- experience fatigue, due to an uneven supply of energy
- feel shaky, weak, and irritable as their blood sugar levels fall
- have difficulty concentrating
For some people, eating only one meal per day may increase the risk of binge eating during the single mealtime. In some cases, following a restrictive diet can even increase the risk of developing a long-term eating disorder, according to some research .
Other problems that may arise include the following:
- The person may find it hard to eat at the single mealtime because they feel full quickly.
- Over time, their desire to eat may increase during the fasting period, rather than decrease, compared with other forms of fasting.
- Body fat may increase, rather than decrease.
- Nutrient deficiencies may occur if a person follows this diet plan long-term.
- The body may start to lose muscle mass as a person enter a state of semi-starvation.
How many calories per day does a person need? Find out here.
Effect on diabetes and cholesterol levels
People with underlying medical conditions may face additional risks. For example, those with type 1 diabetes or low blood sugar need to eat meals regularly throughout each day to maintain a steady blood sugar level.
A 2007 study compared the effect of eating the same number of calories in one or three meals per day for 6 months in a group of healthy adults.
None of the participants experienced a significant weight change, but those who ate only one meal per day experienced a reduction in body fat.
However, their levels of both low-density lipoprotein (LDL) and high-density lipoprotein cholesterol increased, and there was a negative effect on their morning glucose tolerance levels.
Metabolism and body clock genes
A 2012 mouse study suggested that eating only one meal per day may have worsen health, compared with eating two meals. In mice that consumed just one meal per day, there was an increase in body weight, insulin, and fat in the blood. There was also a higher risk of oxidative damage in fatty tissue and the liver.
The researchers concluded that eating one meal per day could negatively impact the genes that help regulate the body clock, sleep-wake cycles, and metabolism.
In another study , this time from 2017, 100 people consumed 25% of their energy needs in food on one day and 125% on the next, alternating days for a year. However, they did not restrict their intake to one meal per day.
Those who practiced this form of intermittent fasting experienced an increase in LDL, or “bad,” cholesterol. High levels of LDL cholesterol may increase the risk of high blood pressure, heart disease, and stroke.
Also, those who fasted in this way did not lose any more weight than those who reduced the number of calories they ate each day.
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