Starting in the 1970s, when the Atkin’s Diet book was first published, low-carb diets have caught the attention of many people trying to lose weight and improve their health. The ketogenic diet (KD), which is both very low in carbohydrates and also very high in fats, has become one of the most talked-about diets in the past several years. With its rise in popularity, it’s no surprise that the keto diet has recently been the focus of dozens of research studies.
Based on what we know from the available research, is the keto diet safe? The evidence is clear that the KD can reliably help to treat obesity and improve insulin resistance, but the long-term impact of the KD on cardiovascular risk factors, liver disease and glucose tolerance is more controversial. Experts agree that genetics seem to play a role in how different people respond to the KD, meaning some may be more likely to thrive on very low-carb diets, while others are more susceptible to developing side effects.
Below we’ll cover the pro’s and con’s of the keto diet in terms of safety, and discuss tips for reducing the chances that the KD will lead to adverse effects.
Ketosis and the Keto Diet
What makes the the ketogenic diet unique among low-carb diets is that it’s characterized by a drastic reduction in carbohydrates (usually less than 30–50 grams per day, depending on individual goals) and also a significant increase in fats, as opposed to protein. The goal of the KD is to enter the metabolic state of ketosis, which happens after a few days of strict carbohydrate restriction.
Eating very-low carb depletes glucose reserves (glycogen stored in the liver and skeletal muscle), which means that glucose is no longer sufficient to provide the body with enough energy and another “fuel source” must be used instead.
This is where dietary fats come into play: depleted glucose reserves leads to the production of ketone bodies that are used as an alternative energy source, especially by the central nervous system, including the brain which has high energy demands. In order to get enough fat and limit carbs, the keto diet includes plenty of foods like meats, eggs, oils, cheeses, fish, nuts, butter, seeds and fibrous vegetables.
Does the keto diet really work when it comes to improving health?
- One of the most promising things about the keto diet is that it helps to reverse obesity, even among people who have struggled on other diets. Obesity is considered a major risk factor for insulin resistance and type 2 diabetes.
- According to a 2017 review published in the journal Nutrients, “diets rich in carbohydrates, and notably rich in refined sugars and fructose, are associated with the metabolic syndrome … carbohydrate restriction has been proposed to be the single most effective intervention for reducing all features of the metabolic syndrome.”
- Studies suggest that the KD helps improve metabolic health markers in several ways: the diet tends to reduce overall caloric intake, increases satiety (fullness after eating), may increase the thermal effect of eating (calories we burn digesting food) due to higher protein intake, and increases gluconeogenesis, which is increased with carbohydrate restriction and is energy demanding.
- Compared to other diets, the keto diet actually has positive effects on appetite control. A major reason that people tend to lose weight and reduce their risk for certain diseases on the KD is because ketosis causes a decreased appetite, thanks to lowering hunger hormones such as ghrelin. It does this even while not negatively affecting levels of leptin, another hormone that regulates appetite, food intake and body weight. Having adequate leptin levels signals to the body that its energy needs are being met and makes weight loss possible.
So, Is the Keto Diet Safe?
Is the ketogenic diet safe long-term? No one is exactly sure. Most studies have looked at the KD’s effects in humans when the diet is followed for up to one to two years or less.
Longer-term studies conducted on animals have shown the KD may be associated with some adverse events. For example, in rodent studies, some will develop nonalcoholic fatty liver disease (defined as liver damage that is not due to excess consumption of alcohol, viral or autoimmune causes, and iron overload ) and insulin resistance when put on the keto diet long-term. Other studies suggest that some individuals may be predisposed to heart-related problems if they eat a very high-fat diet for an extended period of time.
That being said, the keto diet has been shown to be beneficial in many studies, especially among obese men and women. Research shows that the KD can safely help treat conditions including:
- Type 2 diabetes. It can also reduce the need for medications among type 2 diabetics.
- Heart disease. The connection between the ketogenic diet and cardiovascular disease risk factors is complicated. Many studies have found that the keto diet can lead to significant reductions in total cholesterol, increases in HDL cholesterol levels, decreases in triglycerides levels, and reductions in LDL cholesterol levels, as well as potential improvements in blood pressure levels.
- Neurological disorders, including Alzheimer’s, dementia, Parkinson’s and multiple sclerosis.
- Epilepsy and seizure disorders.
- Polycystic ovarian syndrome (PCOS), the most common endocrine disorder among women of reproductive age.
- Certain types of cancer, including prostate, colon, pancreatic and ovarian cancers.
- and others.
Is keto safe for life? In other words, how long is it safe to be in ketosis? As mentioned above, research tells us that the keto diet seems to be safest when followed for about 2–6 months, or up to about two years or so when the individual is being monitored by a doctor.
Disadvantages of the Keto Diet (and Some Dangers)
1. May impact on the liver and kidneys
Some animal studies have found that the KD can contribute to triglyceride accumulation and markers of liver inflammation, possibly because of the higher protein and fat content of the diet compared to other commonly recommended diets (such as the DASH diet or Mediterranean diet for example). (8)
Researchers believe that genetics likely plays a role here, making some people more susceptible to liver problems when following low-carb, high-fat diets. Is the keto diet bad for your kidneys? According to an article released by Harvard Medical School, “Patients with kidney disease need to be cautious because this diet could worsen their condition.”
2. May not lead to improved insulin sensitivity long-term
Is the keto diet safe for diabetics? Most research shows that yes, it is. However, even though the KD can help reduce insulin resistance while someone adheres to the diet’s principles and strictly limits their carb intake, these positive effects may be short-lasting. Results from some animal studies show that insulin resistance/glucose intolerance may potentially be increased once carbs are reintroduced back into the diet.
However, other studies show the opposite to be true, especially among severely obese adults. Researchers, therefore, state that the effects of the keto diet on glucose homeostasis remains controversial and depends on the presence of type 2 diabetes before starting the diet, as well as genetic factors.
3. Can cause side effects
What are the side effects of the ketogenic diet? It’s not uncommon for people beginning the keto diet to experience “keto flu” symptoms, which can include: irritability, cravings, menstruation issues in women, constipation, fatigue, headaches and poor exercise performance. These side effects are due to the body going through major metabolic shifts and essentially withdrawing from carbs and sugar.
In most cases, keto flu symptoms resolve within a few weeks, or even days, especially if someone eats plenty of whole foods, stays moderately active (such as by walking, but not doing high intensity exercise to begin) and gets enough sleep.
4. Might be difficult to maintain weight loss
It’s not totally clear whether weight loss achieved on the keto diet can be maintained by most adults once the diet ends, both because the diet can be hard to follow and due to the body adapting metabolically. Long-term studies conducted on animals show that weight loss tends to level off after about six months on the diet, and sometimes may start to creep back up.
The keto diet is not intended to be followed long-term, which means that individuals need to find another way to maintain a healthy caloric intake, such as by practicing carb-cycling or keto-cycling.
Final Thoughts: Is the Keto Diet Safe?
- When it comes to the question “is the keto diet safe?”, we have to consider both short-term health improvements associated with the KD, as well as unknowns about potential long-term effects.
- Some people seem to be genetically susceptible to experiencing negative effects of the ketogenic diet if they strictly follow the diet for more than about a year.
- Possible dangers of the keto diet include: experiencing short-term keto flu symptoms, struggling to maintain weight loss, failing to improve insulin sensitivity long-term, and potentially increasing the risk for liver, kidney or heart problems.
- Although there are some disadvantages of the ketogenic diet, the diet also supports health in many ways. Ketogenic diet research articles show it can help safely reverse obesity, type 2 diabetes, heart disease, epilepsy, seizures, PCOS, cancer and more.