The keto diet – eating all the fat you want, minus the carbs – can seem like a miracle diet for people who want to lose weight fast while still enjoying their favorite foods. For people who are obese, it can be a golden ticket. Repeated studies have shown that following a keto diet can significantly reduce weight, triglycerides, LDL cholesterol and blood sugar levels. Following a keto diet for the long term can be difficult, and even some of its top advocates warn against sticking to its strict guidelines. This includes reducing carbohydrates to 50 grams a day or less for at least two to three weeks to six to 12 months, according to the National Library of Medicine. Other researchers warn that sticking to this diet for long periods of time may even be dangerous. Here are a few keto diet risks.
Low-Carb Diets Could Lead to Vitamin or Mineral Deficiencies
Limiting carbohydrates to 50 grams a day or less may mean you have to cut back on unhealthy foods like white bread and refined sugar. But it also means you may have to cut back on fruits and certain vegetables, which are also sources of carbohydrates, according to MedlinePlus.
Annette Frain, program director of the Weight Management Center at Wake Forest Baptist Health, says this is a concern, especially if someone is spending more than a few weeks on this type of diet.” She says, “Fruits and vegetables are good for us; they’re high in antioxidants and full of vitamins and minerals.” If you eliminate those, over time, you’re not getting those nutrients.”
It may also be difficult to get enough fiber while you’re cutting carbohydrates so severely, since whole grains are one of the largest sources of this important nutrient. As a result, you may be missing out on many of the benefits of fiber. According to UpToDate, a high-fiber diet can reduce your risk of heart disease, stroke and type 2 diabetes. It can also help with digestive problems, such as constipation or chronic diarrhea.
It May Affect Your Athletic Performance
There’s no shortage of athletes who have jumped on the keto bandwagon, but some researchers worry that they could actually be sabotaging their strength and fitness. In a 2019 study published in the Journal of Sports Medicine and Physical Fitness, researchers found that participants performed worse on high-intensity cycling and running tasks after four days on a ketogenic diet compared to those who’d spent four days on a high-carb diet.
Sure, keto can help athletes lose weight, which can be helpful for speed and endurance. But it’s concerned that people are attributing the benefits of weight loss to something specific in the ketogenic diet. In reality, the benefits of weight loss could be at least partially canceled out by reductions in performance.
Relaxing the Rules Can Cause Weight Regain
But then, people may transition to a more relaxed form of keto that allows for more carbohydrates or less monitoring—sometimes known as lazy keto, keto cycling, or “maintenance mode.” The problem here is that weight regain is almost inevitable.
Keto can be a great jump-start to weight loss, but the reality is that most people can’t adhere to it for very long. Often, people are going into ketosis and losing weight, then coming out and gaining it back and falling into this yo-yo pattern, and that’s not what we want. In addition to being extremely frustrating, these types of weight fluctuations are also linked to a higher risk of early death.
It May Also Damage Blood Vessels
Enjoying a “cheat day” in the short-term on the ketogenic diet can also have long-term consequences, say researchers from the University of British Columbia. In a 2019 study published in Nutrients, they found that indulging in a high-sugar treat (like a large bottle of soda) while on a high-fat, low-carb diet can actually damage blood vessels.
Many of the people going on a keto diet—whether it’s to lose weight, to treat type 2 diabetes, or some other health reason—may be undoing some of the positive impacts on their blood vessels if they suddenly blast them with glucose. The data suggests a ketogenic diet is not something you do for six days a week and take Saturday off.
Too Much Fat Can Raise Chronic Disease Risk
Health experts are concerned that a long-term keto-style diet can affect the heart and arteries. A 2019 study published in the Journal of the American College of Cardiology found that people who practiced a low-carb diet were more likely to develop atrial fibrillation (AFib) than those who ate moderate amounts of carbohydrates. According to the American Heart Association (AHA), this type of arrhythmia raises the risk of blood clots, strokes and heart failure.
It’s not just the heart they’re worried about, either. A 2018 study published in The Lancet found that low-carb dieters who consumed a lot of meat and dairy products had a higher risk of early death compared to those who ate moderate amounts of carbohydrates or mostly plant-based proteins. A 2019 study published in the European Heart Journal also found that people who followed a low-carb, high-fat diet had an increased risk of dying from cancer and all other causes during the study period.
However, most of these studies remain observational, meaning that it was only possible to find associations with certain health outcomes, not cause-and-effect relationships. Overall, there are not enough long-term studies to understand exactly how the ketogenic diet affects the body over a long period of time, or why it seems to affect some people differently than others.
Anyone who is considering trying a ketogenic diet should strive for balance, rather than going for extremes. It is important to look at what you are missing in your diet and what is truly sustainable for you.