Autophagy is a natural process that occurs as your body clears out and replaces damaged cell parts with new ones.

It has been linked to a long list of potential health benefits. For example, some research suggests that it could limit the development of conditions like cancer, type 2 diabetes, and Alzheimer’s disease (1, 2).

Although autophagy occurs constantly within your body, there are several ways to speed the process. These include fasting, exercising, or restricting your calorie intake (3).

Following a low carb, high fat ketogenic diet can also stimulate autophagy by promoting ketosis, a metabolic state in which your body burns fat for energy instead of sugar (4).

Although you cannot physically feel autophagy, it can be associated with noticeable symptoms. These can be caused by changes in metabolism or levels of specific hormones like insulin or glucagon (5, 6).

Here are 6 signs and symptoms of autophagy.

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Ketone bodies are molecules produced from fatty acids when your body doesn’t have enough carbs to use for energy (7).

Research suggests that the production of ketone bodies could stimulate autophagy (8, 9).

Therefore, along with indicating that your body is in ketosis, increased ketone levels can be a sign of autophagy.

To indicate whether autophagy may be occurring, you can easily measure ketone levels in your blood, breath, or urine using special meters or strips.

A key sign of autophagy is reduced appetite. It’s likely due to changed levels of hormones like glucagon and insulin.

Specifically, levels of glucagon tend to increase during autophagy. Glucagon helps manage your blood sugar levels and has been shown to suppress appetite (6, 10, 11).

Meanwhile, insulin levels decrease, which may also reduce your appetite (12, 13).

Some research also suggests that ketosis can reduce levels of ghrelin, also known as the hunger hormone, which could similarly decrease feelings of hunger (14).

Fatigue is associated with many different factors, including autophagy.

Several of the methods used to induce autophagy, including fasting or following a ketogenic diet, have been linked to low energy levels and fatigue (15, 16, 17).

Furthermore, these eating patterns can cause low blood sugar levels, which may also contribute to fatigue (17, 18, 19).

Fortunately, this side effect may only be temporary. Some studies have found that intermittent fasting or following a ketogenic diet may increase energy levels with time as your body adjusts (20, 21).

Keep in mind that fatigue can also be caused by health issues like nutrient deficiencies or psychological conditions. If you’ve been experiencing this symptom for a while, it’s best to consult your doctor to ensure that no underlying health condition is responsible.

If you’re following the ketogenic diet to stimulate autophagy, bad breath is a common symptom that you may notice.

Bad breath can be a sign that your body has entered ketosis. Ketosis increases ketone levels, resulting in autophagy (22).

In particular, the unpleasant odor, often described as fruity or metallic, is due to a type of ketone called acetone (23, 24).

Although this side effect may subside, brushing your teeth more often or chewing sugar-free gum can help keep your breath fresh.

Although no evidence suggests that autophagy increases weight loss on its own, many of the methods commonly used to induce autophagy — including calorie restriction — can lead to weight loss (25).

Some of the other metabolic changes that occur during fasting and ketosis can also boost fat burning and support a healthy body composition. These may include improved insulin sensitivity and the preservation of lean muscle mass (12, 26).

Autophagy also affects the levels of specific hormones, including glucagon, insulin, and ghrelin, thus decreasing your hunger. These effects could promote weight loss by reducing the number of calories that you consume (6, 12, 14).

Additionally, while more human research is needed, some test-tube animal studies suggest that autophagy plays a central role in fat metabolism and could increase lipophagy, which is the breakdown of fat droplets (27, 28, 29, 30, 31).

However, keep in mind that changes in fat metabolism may not necessarily lead to weight loss or reduce body fat.

Therefore, more human studies are needed to understand whether autophagy itself affects body composition.

Studies show that autophagy plays a central role in brain function and maintaining the health of your nerve cells (32, 33).

Interestingly, a 3-year study linked intermittent fasting to improved brain function in older adults with mild mental impairment (34).

Another study including 883 older adults observed similar findings, noting that the beneficial effects associated with intermittent fasting could be due to several factors, including autophagy (35).

In addition to increasing autophagy, ketones are used as an effective source of energy for the brain and could promote brain function (36).

What’s more, some studies suggest that the ketogenic diet may help treat neurodegenerative disorders like Alzheimer’s disease (37, 38).

However, more research on the connection between autophagy and brain health is needed.

While autophagy is associated with several potential health benefits, it’s important to note that the methods used to stimulate it — including fasting, cutting calories, or following a ketogenic diet — may not be suitable for everyone.

In particular, practicing intermittent fasting or following a ketogenic diet is not usually recommended for adolescents, older adults, those who are pregnant, or people with a history of eating disorders.

Furthermore, those with diabetes or other underlying health conditions should talk with their doctor before making any changes to their diet.

Fortunately, there are other options to consider. Besides modifying your diet, adding more physical activity to your routine has been shown to stimulate autophagy (39, 40).

Autophagy is thought to occur in response to stress and muscle contractions while you’re working out. It may even be partly responsible for many of the benefits associated with exercise (40, 41).

According to one review, both endurance and resistance training can increase autophagy (41).

As such, if you’re worried about the potential downsides to achieving autophagy via fasting or limiting your carb intake, becoming more physically active can be the way to go.

Autophagy is a process associated with a variety of health benefits. It occurs as your body removes and replaces damaged cell components.

Autophagy occurs within your body at all times. Still, exercising, fasting, restricting your calorie intake, or following a ketogenic diet can stimulate the process.

Although you cannot feel autophagy directly, it may be associated with several of the signs and symptoms listed above.