What Happens When You Eat One Meal A Day?

Multiple benefits happen when you eat one meal a day like a decrease in blood glucose, an increase in circulating fatty acids, improved insulin sensitivity, an increase in ketone bodies, improved autophagy, decreased blood pressure, improved lipid profile, and brain activity.

In this article, I will list all the benefits that come with intermittent fasting.

what happens when you eat one meal a day

However, eating just one meal a day is one of the toughest ways of intermittent fasting.

Unlike the warrior diet or 16/8, where you can split your meals during a certain eating window, OMAD protocol allows you for just one meal within 1 hour.

So if you’re used to eating three square meals, this shift can feel like a huge step. However, with the big challenges, there are some big rewards.

What Are The Benefits Of Eating One Meal A Day?

Eating one meal a day is not just the ultimate test for hunger tolerance. It also comes with the laundry list of health benefits that happens during an extended period of fast.

In other words, during fasting, many physiological processes change. One of the most obvious changes is shift energy sources from external (the food we eat) into internal (stored body fat).

How much and how significant are those changes will depend on many factors.

OMAD and Blood Glucose

One of the changes that happen during fasting is a reduction in blood sugar levels. If you stop eating for most of the day, just because you eat less food, your blood sugar levels will start to decrease (source).

Think about the body as the sugar bowl. And over the years you eat a lot of food and your body converts that into sugar.

And eventually, as the sugar build-up and it’s not being used then it gets to the point where it overflows.

omad and blood glucose

There are two ways to lower the glucose. Don’t put it in or let the body to burn it off.

So OMAD is a great way to stop adding food (sugar) to the body and start to use what is already stored (fat). That can be really beneficial for people who are looking to control their blood sugar levels using only dietary changes.

OMAD and Fat Adaptation

If you study the human body you know it’s kind of “plastic”. This means it’s extremely adaptable and changeable. If you give me fat, I will adapt and use fat for energy. If you give me sugar, I will adapt again, and use sugar.

If I exercise, my muscle will adapt and grow.

If I stop, it will adapt again, and get smaller.

So the more we fast, the longer we stay without “external” energy sources (food), it will adapt and utilize energy that we have stored (body fat).

This means once the primary source of energy is depleting (glucose) it will break down fat during the process called lipolysis and release fatty acids into the bloodstream.

They will be used as a form of energy (source).

omad fat adaptations

Usually, it takes around 8-12 hours after your last meal for the body to start to shift more towards utilizing fats instead of carbohydrates for energy.

This process takes time to fully switch into fat oxidation. This means the longer you fast, the more significant change you will see.

Does OMAD Put You Into Ketosis?

Doing OMAD will trigger a metabolic switch and put you into ketosis. The body turns from external sources (food) into internal sources (stored energy). In response to low glucose levels, the liver starts the process of ketone body synthesis to produce ketone bodies.

One of the primary reasons why people start intermittent fasting is weight loss.

One meal a day offers a significant caloric restriction that puts us into a caloric deficit literally on day one. Some of the studies refer to this as a “metabolic switch” (source).

picture of ketosis

A caloric deficit means that we deliver less energy to our body than is required. In that state, our body will still use energy.

However, this energy won’t come from the food that we eat, but from the fat cells.

The so-called metabolic switch starts when glycogen stores in the liver are depleted. During this time liver is trying to “produce” glucose from non-glucose sources (aka fatty acids).

During this process, the liver takes up the fatty acids from the blood, where they are oxidized to β-hydroxybutyrate and acetoacetate. That’s when the liver starts to manufacture ketone bodies.

Ketone bodies then can be used as an energy source. The longer the fast, the more ketone bodies you manufacture.

One of the characteristic indicators that tell us we are in ketosis is the smell of acetone from our breath and from our urine.

Other Health Benefits Of OMAD

OMAD and Insulin Resistance

Whenever you have a meal, your blood sugar will rise. The function of insulin is to signal to your body and eliminate excess sugar from the blood and push it to your system (muscle, liver, or fat cells) (source).

Insulin is an anabolic hormone. This means every time when you have high insulin, your body stores the energy instead of using it. In other words, we get fat.

omad and insulin resistance

The problem is when we eat too much, too often, we have a lot of spikes of insulin and that can lead to insulin resistance and pre-diabetes.

So by doing OMAD or any other form of intermittent fasting will lead to reduce in sugar intake, therefore will decrease in insulin spikes.

After a period of fasting, insulin sensitivity rises and insulin levels decrease.

This is great news, especially for people who have problems with diabetes. A number of studies confirm that intermittent fasting is a great way to control insulin, therefore diabetes (source).

A small study from Toronto showed great results with Type 2 Diabetes (as well as other metabolic problems like hypertension )patients (source)..

Patients, who had the disease for 10 to 25 years did 24-hour fast every other.

Within one to four weeks, their blood sugar improved, and was able to stop using insulin.

Related article: Is One Meal A Day Good For Diabetes?

Meal Frequency and Insulin Sensitivity

Intermittent fasting in the form of one meal a day improves insulin sensitivity and gives the pancreas a break in the constant production of insulin (source).

Insulin resistance is a major metabolic problem that leads to obesity and a number of diseases, including type 2 diabetes.

People with insulin resistance will require more insulin to shuffle the sugar away from the blood. This means each time you have a meal your body produces more insulin than it should.

Over time, this may affect your pancreas to stop producing insulin, and the body starts asking for more insulin to control sugar in the form of injections.

On the flip side, insulin sensitivity is the ability to use minimum insulin to do the job.

This means you just need a little bit instead of a lot.

insulin sensitivity

Does OMAD Lower Blood Pressure?

Studies show that intermittent fasting with one meal a day of 200–250 kcal for 4-21 days has a beneficial effect on lowering blood pressure due to the increase in parasympathetic activity, increased norepinephrine elimination through the kidneys, and improved insulin sensitivity.

In recent years there have been many studies done on intermittent fasting that look beyond the weight loss benefits. Some of them show that prolonged fast can improve many cardiovascular problems (source).

sympathetic vs parasympathetic nervous system

One of the benefits is a reduction in blood pressure. It is not clear if such an effect is due to calorie restriction, or to fasting.

However, because of the simplicity of fasting, it seems to be a much more sustainable way to achieve a calorie deficit.

Hypertension is one of the most common health issues of the modern world. In the United States alone, there are 86 million adults who suffer from this high blood pressure (source).

Hypertension occurs when systolic blood pressure exceeds 140 mmHg, and diastolic blood pressure exceeds 90 mmHg.

This is associated with increased activity of the sympathetic nervous system, release of epinephrine and norepinephrine, and increased heart rate. 

Extended fast seems to activate the parasympathetic nervous system that is associated with lowering blood pressure.

In one study, 1610 people were fasting for 4 to 41 days with a daily intake of ~250 kcal. Groups were divided into medicated and none dictated. 

The results showed that all of the participants reduced their blood pressure and 23% of medicated participants stopped taking their medications (source).

Does OMAD Cause Autophagy?

Studies show that intermittent fasting and caloric restriction might represent a simple, safe and inexpensive way to increase neuronal autophagy and slow down cellular senescence. Cellular senescence is the process of aging the cell, where cells cannot divide and regenerate anymore.

When our cells senesce they stop growing and repairing, they release pro-inflammatory chemicals like macrophage inflammatory proteins (IL- 6, IL- 8).

This basically means those are tissue-destroying, grumpy, useless, and unhelpful cells that make more harm than good (source).

omad helps with autophagy

Cellular senescence is inevitable. However, it can be either speed up or slowed down. Things that speed cellular aging are environmental toxins, free radical damage, chronic stress, poor diet, lack of deep sleep, etc.

But we also can slow it down through apoptosis and autophagy where cell removes unnecessary or dysfunctional components.

Fasting and caloric restriction seems to slow down cellular senescence and increase autophagy.

OMAD and Mental Health Benefits

Intermittent fasting can improve brain health and cognitive function. In fact, more than 2,400 years ago Hippocrates wrote that fasting can prevent or lower the effects of epilepsy (source).

Also, the latest research shows that ketosis activates neuronal network activity. So any diet that puts us into ketosis (fasting and ketogenic diet) can benefit many patients with epilepsy (source).

So how does fasting is actually helping the brain? Throughout our lives, our brain is generating a new bunch of neurons.

The generation of new neurons is called neurogenesis. Neurons are brain cells that are linked with each other by synapses.


According to studies, intermittent fasting helps with the survival of newly generated neurons, and running enhances the proliferation of the stem cells (source).

This means when we run we get more fresh neurons in the brain, and when we fast those neurons get stronger.

The way we remember, learn new things, respond emotionally to situations, and have a motor control proper functioning is thanks to glutamate activity in the neurons. Glutamate is the neurotransmitter in the CNS, essential for all behaviors.

Intermittent fasting enhances glutamate activity in the synapses, therefore it enhances long-term memory formation (source).

Does Fasting Make You Smarter?

Some people report feeling “mentally sharp” after extended fasting. They report being more productive, and more focused. Some indigenous cultures used fasting as a way to spike their creativity.

On the other hand, others have reported feeling worse than before. They reported to feel clouded, irritated, and distracted. Also people experienced insomnia, lethargy and anxiety.

This usually happens when people have too much going on in their lives and intermittent fasting, just like any other micro-level stress, adds up to the total stress level.

This is called the hormesis effect.

The dose-response effect on the body after the stimulus. Some people who have low-level of stress may thrive on fasting, where others who have more stress in their life will crash.

Related article: Can You Do OMAD Every Day?

If you have a 20-year old college student who’s got no health issues, no real responsibilities, and wants to use fasting as a way to lose extra 5 pounds he may experience additional mental sharpness.

But if you take 50-year old women who want to lose 50 pounds, but she works 12-h day shifts, takes several medications, has financial debt, and sick parents, her stress levels will be much much higher.

She may feel exhausted after fasting and experience multiple symptoms of fogginess and anxiety.

That’s why intermittent fasting is not one size fits all. Because there are other factors, like genetics and personal background, that will determine the effectiveness of the fast.

Improves Cholesterol And Lipid Profile

There are over 95 million Americans diagnosed with high cholesterol above 200 mg/dl (source) and many of them are looking for an alternative treatment that doesn’t require taking statins.

Becasue apart from weight loss, intermittent fasting improves the lipid profile in the body. This means it can reduce total cholesterol, LDL, triglycerides and increasing HDL levels (source).

omad improves lipid profile

That’s why intermittent fasting has become a very popular way to improve health and reduce some of the symptoms of the most common health issues, including cholesterol and lipid profile.

It is unknown if the health benefits are due to general caloric restriction or to intermittent fasting.

Some of the studies tried to compare those two approaches, but with the number of limitations and patient compliance differences, it is hard to establish a hard conclusion.

They also tried to compare different forms of fasting.

For instance, 25 obese adults were divided into two groups. One group was doing alternate-day fasting (ADF) where you eat for 12 hours and then you fast for another 36 hours.

Another group was on daily calorie restriction with 400 calories less than usual.

After 8 weeks, there was a significant improvement in weight loss and cholesterol levels in both groups. But there was no difference between each group.

So my personal conclusion is that regardless of what type of fasting you do, one meal a day, ADF, or simply restriction of calories, it will all lead to the same lipid profile benefits.

Related article: Is OMAD Better Than ADF?

Improves Cellular Signaling

For health and longevity, our cells need correct chemical communication. When this breaks down, our bodies start to fall apart.

It’s kind of like forgetting the language that we’ve been learning in high school. When you’re young, you remember all the verbs. But when you get older, and you don’t practice, you can hardly say anything.

When you don’t use it, you lose it.

Our cells need some effective form of communication. This happens through cellular signaling. Intermittent fasting and caloric restriction seem to improve many of the cellular signaling pathways.

For example.

  • Antioxidant signaling. Our bodies have their own antioxidant system that cleanses the “toxins”. However, as we age those systems become less efficient and slow down. Intermittent fasting helps with the gene expression of those systems and slows down the “rusting” effect.
  • AMPK (activated protein kinase) signaling. AMPK is an energy sensor that orchestrates a cellular network of signaling responsible for our health and longevity. AMPK is stimulated by low energy intake. Intermittent fasting seems to activate AMPK, improving its lifespan and overall health.
  • Insulin and insulin-like growth factor-1 (IGF-1) signaling. Insulin and IGF-1 are both anabolic hormones. They stimulate growth. However, if those hormones are too high, for too long, this can lead to a greater risk of cancer.

Downregulating (decreasing activity) of those hormones can improve their signaling and extend lifespan.

Decrease Risk Of Cancer

There is extensive research suggesting that intermittent fasting can play a role in cancer treatment and cancer prevention.

Fasting or fasting-mimicking diets lead to inhibition in growth and in metabolite levels. This means they can reduce the capability of cancer cells to adapt and survive (source).

So the combination of intermittent fasting with traditional chemotherapy, immunotherapy, or other treatments seems to increase treatment efficacy.

Also, increased body weight and obesity are estimated for 14% – 20% of all cancer-related factors in the US (source).

Some of the studies that are done on rodents suggest that intermittent fasting and caloric restriction have powerful anticancer effects, including the ability to trigger anticancer immunity.

Lastly, some of the patients do not respond effectively to the cancer drugs because cancer cells can adopt metabolic strategies leading to survival. This means they got really resistant to medicine (source).

Those metabolic processes are much more difficult for cancer cells to survive under fasting conditions.

Michal Sieroslawski

Michal is an exercise physiologist (MSc) and a veteran endurance athlete. He loves to experiment and share his successes and failures to help busy men and women who want to lose weight.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts