What Are the Pros and Cons of a Ketogenic (Keto) Diet?

You probably know keto as a high fat, low carb fat diet. But it’s very high fat — and likely much higher than you think.

There are two types of keto: standard and therapeutic. Standard is what you might try if you want to do keto for general health and weight loss, and therapeutic is used by healthcare professionals when treating conditions like epilepsy. Their macro breakdowns look slightly different:

Keep in mind that keto isn’t the same thing as a standard low carb diet. Most low carb diets aim to keep carbs under 150 grams (g) per day, which is equivalent to about 6 bananas. On a keto diet, you’ll be sticking to under 50 g per day, which is necessary to reach ketosis.

The metabolic state ketosis is where the diet’s purported health benefits come from. Once your body processes fats in the liver, it produces ketone bodies, molecules that can be used for energy. However, you can only reach ketosis once your body has used up all its available carbs.

Helps with faster weight loss

While this sounds promising, there’s an immediate caveat — basically all the research on keto for weight loss has been done on people with obesity. So if you’re looking to use this diet to lose the last 5 pounds, you may not see the same results.

But for people with a significant amount of excess body weight, a keto diet can be an effective choice for weight loss.

There are a few reasons for this. First, cutting carbs means you’ll drop water weight, which you’ll see quickly on the scale. After the first couple of weeks, this rapid “weight loss” will slow to a more normal pace.

While this initial drop in pounds isn’t fat loss, the fast results can be a motivating factor for many people, helping them continue with the diet. Research also suggests that certain types of ketones released during ketosis may play a role in appetite suppression, which can make it easier to stick to a calorie deficit.

Eating low carb foods might also make it easier for your body to burn fat. According to research from 2022, keto may reduce insulin spikes. Insulin stops lipolysis, the process by which your body breaks down stored fat, so keeping blood sugar levels stable might make losing body fat easier.

Can help with blood sugar management in type 2 diabetes

There’s been a lot of research on keto for type 2 diabetes, and for good reason. Low carb diets have been a mainstay of diabetes management, and they were recommended well before injectable insulin became available.

So while low carb diets for diabetes are nothing new, keto provides a novel approach by upping the fat content. It’s well established in the research that keto and low carb diets can help stabilize blood sugar, but there may actually be more potential benefits at play.

One 2019 study found that a keto diet reversed type 2 diabetes in some participants, and after a 2-year follow-up, many participants had improvements in their diabetes blood markers. Among participants, there was a diabetes remission rate of 17.6%.

However, the diet isn’t without its drawbacks. A 2021 meta-analysis found that the benefits seemed to decrease after 1 year, and many participants found it hard to stick to for a long period of time. This means that a slightly less restrictive, sustainable eating plan may yield better long-term results.

May ‘starve’ cancer cells of energy

While the research on keto as part of cancer treatment is new — and highly controversial — some small studies have shown possible benefits.

The idea behind this is related to something called the Warburg effect. This claims that there are metabolic changes in cancer cells that mean they primarily use glucose (carbs) for energy, even when oxygen is available.

Theoretically, a keto diet that cuts down on carbs and forces the body to rely on fat for fuel might “starve” cancer cells. This could potentially weaken cancer cells, making them more susceptible to chemotherapy and radiation, while protecting normal cells.

One small 2023 study found a better overall survival rate in participants who continued the keto diet for longer, but experts note that this research is still in its early stages.

May reduce your risk of cardiovascular disease

Like many of the potential benefits of keto, the research on this is also conflicting, but some experts claim that keto could be good for heart health.

While a 2023 meta-analysis showed a decrease in blood triglycerides, it also showed increases in both HDL (good) cholesterol and LDL (bad) cholesterol. Another showed no significant increase in LDL.

It’s thought that the makeup of your keto diet plays a role in changes to triglycerides, HDL, and LDL. For example, eating more saturated fat can cause an increase in LDL, which is bad for heart health. But eating more healthy unsaturated fats like avocado and salmon can increase HDL, which is good for heart health.

Therefore, it’s perhaps not so much the keto diet itself that directly improves blood markers for cardiovascular health, but rather the types of fats you’re eating on a daily basis.

Can cause nutrient deficiencies

Because the keto diet limits carbs to just 50 g, it doesn’t leave room to include many fruits or vegetables. These are your body’s primary source of essential vitamins and minerals, all of which play a role in keeping your cells healthy.

Most notably, keto diets are often low in vitamins A, E, and B6, as well as folate, calcium, magnesium, potassium, and iron.

If you’re trying keto, you can mitigate some of these deficiencies by eating plenty of low carb vegetables like leafy greens, broccoli, asparagus, and zucchini. It’s also a good idea to work with a registered dietitian if you’re planning on following the diet for an extended period of time.

May cause digestive issues

Staying low carb means you won’t be eating many beans, lentils, or whole grains, which are all good sources of fiber. This can lead to constipation and slow digestion.

Consuming so much fat can also be tough on your digestive system. Many people who try keto experience gastrointestinal (GI) issues like diarrhea, cramping, bloating, and stomach upset.

Could be bad for heart health

While we discussed the possible benefits on heart health earlier, we also touched on the risks. If you’re eating a keto diet that’s high in sources of saturated fat — like meat, cheese, and butter — you’re at risk of harming your heart health.

Saturated fat is known to increase levels of LDL (bad) cholesterol, which can clog your arteries. This is associated with heart and cardiovascular disease.

Can be hard to stick to

Sticking to a keto diet can be tricky, and it’s not easy to do long term. There’s also no long-term data on its safety, so it’s not something you’d want to do without the supervision of a healthcare professional.

Following a keto diet requires a lot of meal planning and food preparation, and this can be incredibly challenging for people with busy jobs and families. It’s also hard to find keto-friendly options at restaurants and social gatherings, so some people find it negatively affects their social life.

If you find that a lower carb style of eating feels good for your body, trying a more relaxed approach — like a low carb Mediterranean style diet — might be a simpler, more sustainable choice.

While proponents of the keto diet may shout about its endless benefits, there are some important risks to be aware of. For instance, eating a high fat diet can negatively affect your heart health and cause GI issues. There’s also no long-term data on the safety of keto.

However, for people with obesity and type 2 diabetes, the benefits of keto might outweigh the risks.

If you want to try keto, it’s a good idea to speak with your doctor or a dietitian, especially if you have any health conditions. They can advise you on how to do the diet as safely and sustainably as possible.