Why Do I Have No Appetite on Keto? (...and what to do)

Why Do I Have No Appetite on Keto? (...and what to do)
Daniel Thompson

on June 06, 2019

A decrease in appetite is usually a bad sign. It often happens when we’re sick, stressed out, or otherwise traumatized. However, for those who want to lose weight, appetite is one of the greatest challenges to overcome. And diets especially have a tendency to make people feel hungrier, creating a never-ending battle between an individual and what they eat.

However, when it comes to the ketogenic diet, people tend to experience hunger and appetite differently. Followers of the keto diet consistently report a reduction in appetite, even as they lose weight.

Today, we’re going to examine the mechanisms behind ketosis and appetite in order to understand why the keto diet makes people feel less hungry.

What Is Ketosis?

In order to understand the effects of the keto diet on appetite, it’s important to discuss the metabolic process around which the diet is based. Ketosis is the driving mechanism of the ketogenic diet, and the concepts behind it are pretty simple.

On a normal diet — one that includes carbohydrates — the body breaks down carbs into glycogen, a simple sugar that the body then uses as energy in order to perform all sorts of different bodily functions.

When carbs are scarce, like on the keto diet, the body switches its fuel source from glycogen to ketone bodies, which are made in the liver from the body’s excess fat stores. Ketone bodies act as an alternative energy source to keep everyday processes from shutting down when carbs are scarce.

In ketosis, ketone bodies play a key role in weight loss. Unlike carbohydrate-derived energy, excess ketone bodies they are not stored when excess amounts are produced. Instead, the kidneys filter them out of the blood, and the body passes them as waste.

Because it takes a large change in diet in order to start and maintain ketosis, the process itself can have drastic effects on a participant’s appetite. However, before we explore how ketosis affects appetite more deeply, it is important to understand the difference between appetite and hunger.

Appetite vs. Hunger

While the two terms are used somewhat interchangeably, hunger and appetite have very different meanings when it comes to science and nutrition.

Hunger is the urgent need for food due to lack of eating. It’s a notable feeling of discomfort and is determined by the actual emptiness of the stomach. This feeling that we experience every day is actually the end result of a series of chain reactions due to a chemical signal sent from the stomach to the brain, telling you to eat.

Appetite, on the other hand, is a whole different story. Appetite is a desire to eat, usually after seeing, smelling, or thinking about food. Humans are capable of experiencing appetite regardless of how long it’s been since they’ve eaten.

For many, appetite is often associated with cravings and has little to do with the actual dietary needs of the body. It’s also the mechanism that tells our body to stop eating, even when we may still need to take in nutrition. This occurs often when people are ill or feel stressed.

Scientists can measure hunger in terms of the hormones leptin and ghrelin. Leptin is the hormone responsible for suppressing appetite, where ghrelin is responsible for increasing it. While researchers have identified these two critical hormones and understand their association with generating hunger signals, it’s not clear exactly how these hormones function within the body and the exact responsibilities each plays.     

Why Does Keto Give You No Appetite?

So why does keto give you no appetite? Scientists actually aren’t sure, but they have proven in studies and meta-analyses that keto-diet participants feel less hungry and (more importantly) don't feel an increase in appetite, even as they reduce calories and lose weight.

While scientists are unsure of the cause of this side effect, they do have a few theories:


Some researchers postulate that the process of ketosis itself is the cause for decreased appetite on the keto diet. In studies that compared keto diets with other low-energy diets, both study groups saw decreases in appetite.

While the two types of diets studied are very different from one another, the thing they both have in common is the presence of ketones. Because of this, scientists deduce that decreased appetite hormones may stem from the process of ketosis itself.  

More Vegetables and Protein

Many keto-friendly foods are not just high in fat, but also provide a good source of protein. Because of this, people on the keto diet may eat more protein than they were eating when the majority of their calories came from carbs.

Additionally, keto followers may be eating more vegetables as well. Studies have shown that protein is one of the most satiating nutrients, which may result in longer-lasting feelings of fullness and a decrease in appetite on the keto diet.

Low Carbohydrates

Restricting carbohydrates, especially refined carbohydrates, may be another reason why the ketogenic diet reduces appetite. When you consume refined carbs, your blood sugar levels spike, causing your body to take those carbs and store them away for later. Because that energy is stored and no longer available, your body quickly sends more hunger signals to the brain.

On a keto diet where carbs are scarce, blood sugar spikes are practically non-existent, erasing those hunger signals that your body would have produced if you had eaten carbs.

Keto and Fatigue

Because keto can reduce appetite but not hunger, those following a keto diet can still experience symptoms associated with starvation, yet still not feel the urge to eat. Side effects of this can include lightheadedness, feelings of fatigue, and other symptoms that many have dubbed the “keto flu”.

Other symptoms of the keto flu can include dizziness, nausea, irritability, digestion issues, and insomnia. It is important to note that these symptoms typically only last a week, with dieters reporting that they feel back to normal after their bodies get used to ketosis. In rare cases, keto flu symptoms may last up to six weeks.

Once you’re through that keto flu period, you should start to feel more energy in your daily activities.

When You Should Be Worried

While some people welcome the appetite-reducing effects of the keto diet, it can be a frightening experience for others who are accustomed to set food amounts and a rigid eating schedule. Many people on the keto diet describe their appetite experiences as a wave-like pattern as they progress through the beginning of their keto journey.

In the beginning, you may experience a dramatic increase in appetite. This occurs because your body is using up the last of its carbohydrate fuel and is running on empty. The body sends hunger signals to the brain, asking to eat more food.

After the first few days of keto, your hunger levels may reverse, leaving you feeling less hungry than ever before. Some people struggle to hit their target calories for the day, feeling full after just a few bites.

Eventually, the body gets used to its new energy source and balances out hunger levels. Most people still feel less hungry than they do while on a full-carb diet, but don’t have difficulty eating or hitting their target macros for the day.

If an individual is still experiencing drastic side effects of appetite suppression after six weeks, it may be time to consult a physician or nutrition professional.

How To Get Yourself To Eat When You Have No Appetite

If you find yourself panicking due to lack of appetite, the most important thing to do is to not worry. Everybody reacts to the ketosis process differently. The keto diet asks a lot of your body, so give it a break while it is in transition.

The second thing to remember is to not force yourself to eat. While you may be used to eating three square meals a day, the ketogenic diet can drastically alter this pattern. If the plate in front of you seems overwhelming, just eat what you feel comfortable with eating.

Many people who experience this period of decreased hunger choose to skip full-blown meals altogether, instead opting for a few smaller meals or keto snacks spread out across the day.

In Summary

Ketosis transforms the body in many different ways — it really shows us how many different aspects of life are affected by the things we eat.

Appetite plays a large role in eating habits, diets, and weight loss. While it is different from hunger in many ways, appetite still affects how we feel about food, and often is the mechanism that gets us to eat when we do.

The keto diet can throw hunger and appetite levels for a loop, which can be an unnerving experience for many. The important thing to remember is that every keto journey starts out with an imbalance, and then slowly, our bodies adjust to a new normal. From there, our ability to lose weight and get fit can change dramatically for the better.

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