Obesity and metabolic diseases are major health problems worldwide.
In 2016, obesity affected 13% of adults globally (1Trusted Source).
Obesity is a risk factor of metabolic syndrome, a cluster of metabolic abnormalities, including type 2 diabetes, high blood pressure, high waist-to- hip ratio, and low HDL (good) cholesterol. (2Trusted Source, 3Trusted Source).
To combat this, many diets have emerged, including the ketogenic diet, in which a person consumes a very limited amount of carbohydrates. Some research suggests this diet may have benefits for people with obesity (4Trusted Source).
However, some experts have questioned the health benefits of the keto diet and called for more research. While it may help you lose weight, there may also be complications (5Trusted Source, 6Trusted Source).
This article explains how the keto diet may help people lose weight and manage metabolic disease. It also discusses some of the possible drawbacks.
A ketogenic diet is high in fat, moderate in protein, and low in carbs (6Trusted Source).
As carbs are reduced and fat is increased, the body enters a metabolic state called ketosis. Then the body starts turning fats into ketones, which are molecules that can supply energy for the brain (6Trusted Source).
After a few days or weeks on such a diet, the body and brain become very efficient at burning fat and ketones for fuel instead of carbs.
The ketogenic diet also lowers insulin levels, which can be beneficial for improving insulin sensitivity and blood sugar management (7Trusted Source, 8Trusted Source).
Staple foods on a ketogenic diet include:
- heavy cream
- low carb vegetables
In contrast, nearly all carb sources are eliminated, including:
- some higher carb vegetables
Bottom Line: A ketogenic diet is a high-fat, moderate-protein, and low-carb diet. It primarily works by lowering insulin levels, producing ketones, and increasing fat burning.
There’s evidence that ketogenic diets can help with weight loss.
They may help you lose fat, preserve muscle mass, and improve many markers of disease (9Trusted Source, 10Trusted Source, 11Trusted Source, 12Trusted Source).
Some studies have suggested that a ketogenic diet may be more effective than a low fat diet for weight loss, even after matching the total calorie intake (11Trusted Source).
In one older study, people on a ketogenic diet lost 2.2 times more weight than those on a low calorie, low fat diet. Triglyceride and HDL (good) cholesterol levels also improved (13).
However, both groups reduced calorie consumption by a comparable amount, and this may have increased weight loss (13).
You can see typical weight loss results on this graph (13):
Another 2007 study compared a low carb diet to the Diabetes UK’s dietary guidelines. It found the low-carb group lost 15.2 pounds (6.9 kg), while the low fat group lost only 4.6 pounds (2.1 kg). Over 3 months, the low-carb diet caused 3 times more weight loss (14Trusted Source).
However, there was no difference in HbA1c, ketone, or lipid levels between the groups. Also, those on the low-carb diet also decreased their calorie intake. Finally, there was no difference in fat or protein intake between the two groups. This is important to note if people are increasing their fat intake because they are following a keto diet.
However, there are contrasting theories for these findings. Some researchers argue the results are simply due to a higher protein intake, and others think there’s a distinct “metabolic advantage” to ketogenic diets (15Trusted Source, 16Trusted Source).
Other ketogenic diet studies have found that the ketogenic diet may lead to reductions in appetite and food intake. This is extremely important when applying the research to a real-life setting (17Trusted Source, 18Trusted Source).
If you dislike counting calories, the data suggests a ketogenic diet may be a good option for you. You can eliminate certain foods and don’t have to track calories.
If you follow the keto diet, you still have to check labels and keep track of your total grams of carbs each day, which requires paying attention to food choices.
However, keep in mind that many of the studies mentioned above had small sample sizes and only evaluated the short-term effects of the diet.
Additional research is needed to determine how the diet may impact weight loss in the long run and whether weight is regained once a normal diet is resumed.
Bottom Line: The ketogenic diet is an effective weight loss diet that’s well-supported by evidence. It is very filling and usually does not require calorie counting.
Here’s how ketogenic diets promote weight loss:
- Higher protein intake. Some ketogenic diets lead to an increase in protein intake, which has many weight loss benefits (15Trusted Source).
- Gluconeogenesis. Your body converts fat and protein into carbs for fuel. This process may burn many additional calories each day (19Trusted Source, 20Trusted Source).
- Appetite suppressant. Ketogenic diets help you feel full. This is supported by positive changes in hunger hormones, including leptin and ghrelin (21Trusted Source).
- Improved insulin sensitivity. Ketogenic diets can drastically improve insulin sensitivity, which can help improve fuel utilization and metabolism (22Trusted Source).
- Decreased fat storage. Some research suggests ketogenic diets may reduce lipogenesis, the process of converting sugar into fat (23Trusted Source). This is because excess carbs are stored as fat. When there’s a minimal intake of carbs, fat is used for energy.
- Increased fat burning. Several studies have found that ketogenic diets may slightly increase the amount of fat you burn during rest, daily activity, and exercise, although more research is needed (24Trusted Source, 25Trusted Source).
In these ways, a ketogenic diet can be effective at helping you lose weight.
However, note that it’s important to ensure that you’re meeting your calorie needs when following the ketogenic diet. Cutting calories too much can slow your metabolism, making it harder to lose weight in the long run (26Trusted Source).
Some experts also note that, while the keto diet may lead to weight loss in the short term, the loss is unlikely to continue. It can also be hard to follow the diet for a long time (6Trusted Source).
Bottom Line: A ketogenic diet may help you burn fat, reduce calorie intake, and increase feelings of fullness, compared to other weight-loss diets.
Our free assessment ranks the best diets for you based on your answers to 3 quick questions.
Metabolic syndrome describes five common risk factors for obesity, type 2 diabetes, and heart disease (2Trusted Source):
- high blood pressure
- high waist-to-hip ratio (excess belly fat)
- high levels of LDL (bad) cholesterol
- low levels of HDL (good) cholesterol
- high blood sugar levels
Many of these risk factors can be improved — or even eliminated — with nutritional and lifestyle changes (27Trusted Source).
Insulin also plays an important role in diabetes and metabolic disease. Ketogenic diets are extremely effective for lowering insulin levels, especially for people with type 2 diabetes or prediabetes (Trusted Source7Trusted Source, 8Trusted Source).
One older study found that after only 2 weeks on a ketogenic diet, insulin sensitivity improved by 75% and blood sugar dropped from 7.5 mmol/l to 6.2 mmol/l (28Trusted Source).
A 16-week study also found a 16% reduction in blood sugar levels. Additionally, 7 of the 21 participants were able to completely stop all diabetic medication (29Trusted Source).
What’s more, some studies in humans and animals have also found that the ketogenic diet could reduce levels of total cholesterol and triglycerides (30Trusted Source).
However, note that most available research is only focused on the short-term effects of the ketogenic diet.
In fact, some older studies suggest that the ketogenic diet may actually negatively affect heart health, particularly in children (31Trusted Source, 32Trusted Source).
Additionally, although research shows that saturated fat intake is not linked to a higher risk of heart disease directly, it may increase levels of LDL (bad) cholesterol, which is a risk factor for heart disease (33Trusted Source).
Furthermore, several studies also show that consuming high amounts of some types of fat may be associated with a higher risk of certain types of cancer (34Trusted Source, 35Trusted Source, 36Trusted Source).
Therefore, more research is needed to determine how the ketogenic diet may affect health and disease long term.
Bottom Line: Ketogenic diets can improve many aspects of the metabolic syndrome, a major risk factor for obesity, type 2 diabetes, and heart disease.
There are several key factors that explain the drastic effects of the ketogenic diet on markers of metabolic disease. These include:
- Fewer carbs. A high carb diet can constantly elevate blood sugar and insulin levels, which can decrease the body’s ability to use insulin efficiently (9Trusted Source).
- Decreased insulin resistance. Insulin resistance can cause health issues like inflammation, high triglyceride levels, and fat gain (8Trusted Source).
- Ketone bodies. Ketone bodies — molecules produced during ketosis — may help protect against some diseases, such as cancer, Alzheimer’s, and epilepsy (37Trusted Source, 38Trusted Source, 39Trusted Source).
- Inflammation. The ketogenic diet can drastically reduce chronic inflammation, which is linked to metabolic syndrome and various diseases (40Trusted Source, 41Trusted Source, 42Trusted Source).
- Fat loss. This diet promotes the loss of body fat, especially unhealthy abdominal fat. Excess fat in the abdominal area is one of the criteria for metabolic disease (43Trusted Source).
- Restore normal insulin function. Research has shown that healthy insulin function can fight inflammation, while poor insulin function can increase it (44Trusted Source).
As you can see, the combination of these factors plays a rather remarkable and important role in health and protection against disease.
Bottom Line: Ketogenic diets may improve metabolic health by improving insulin function, lowering inflammation, and promoting fat loss, among others.
If you want to try a ketogenic diet, follow these basic rules:
- Eliminate carbs. Check food labels and aim for 20 to 50 grams of carbs or fewer per day (8Trusted Source).
- Stock up on staples. Buy meat, cheese, whole eggs, nuts, oils, avocados, oily fish, and cream, as these are now staples in your diet.
- Eat your veggies. Fat sources are high in calories, so base each meal on low carb veggies to fill your plate and help keep you feeling full. Veggies will also provide fiber, which you’ll no longer be getting from whole grains, beans, or legumes.
- Experiment. A ketogenic diet can still be interesting and tasty. You can even make ketogenic pasta, bread, muffins, brownies, puddings, ice cream, etc.
- Build a plan. It can be hard to find low carb meals for when you’re on the go. As with any diet, it’s important to have a plan and go-to snacks or meals.
- Find what you love. Experiment until you find the ultimate keto diet for you.
- Track progress. Take photos, measurements, and monitor your weight every 3 to 4 weeks. If progress stops, re-examine your daily intake. Make sure you’re getting enough vegetables at every meal and keeping portion sizes moderate.
- Replace fluids. Make sure you’re drinking enough water and getting proper amounts of electrolytes, like sodium, potassium, and magnesium.
- Be consistent. There’s no shortcut to success. With any diet, consistency is the most important factor.
You may also wish to monitor ketone levels in either urine or blood, since these let you know whether you’re keeping carb levels down sufficiently to achieve ketosis.
Based on current research, studies at my lab, and continuous testing with clients, anything over 0.5–1.0 mmol/l demonstrates sufficient nutritional ketosis (45Trusted Source).
Before switching to this type of diet or using any type of supplement, ask your doctor or a dietitian for advice.
Bottom Line: Base most of your meals on low carb veggies and high fat meats, fish, or eggs. You may also wish to monitor your ketone levels.
No single diet is suitable for everyone, especially since individual metabolism, genes, body types, lifestyles, taste buds, and personal preferences differ.
It can benefit people with obesity or who have a higher chance of developing metabolic syndrome, but it’s not suitable for everyone. For example, it’s not suitable for people with the following conditions (7Trusted Source):
- liver failure
- disorders of fat metabolism
- carnitine deficiency
- pyruvate kinase deficiency
There may also be some negative effects. When you first start the diet, you may experience flu-like symptoms, known as “keto flu.”
This may include poor energy and mental function, increased hunger, sleep issues, nausea, digestive discomfort, and poor exercise performance.
Researchers have not yet done enough long-term investigation to find out precisely what the long-term effects might be, but there may be a risk of kidney or liver problems.
There’s also a risk of dehydration, so you need to drink plenty of fluids, especially water, while following this diet (8Trusted Source).
Always speak to a doctor before starting a ketogenic diet to ensure that it’s safe and suitable for you.
A ketogenic diet can also be hard to stick to. If you can’t follow it but still like the idea of a low carb diet, then carb cycling or a standard low carb diet may be a better option for you.
A ketogenic diet may also not be the best option for elite athletes or those wishing to build large amounts of muscle.
Additionally, vegetarians or vegans may struggle with this diet, due to the key role meats, eggs, fish, and dairy play.
Bottom Line: The ketogenic diet can provide amazing results if you stick to it. However, it may not be the best option for everyone.
In order to get the most out of a ketogenic diet, you must eat high fat foods and limit your carb intake to fewer than 30–50 grams per day.
If you follow a ketogenic diet with medical supervision, it can help you lose weight, and it may enhance your overall health.
It may reduce your risk for type 2 diabetes, obesity, and other aspects of metabolic disease.
Before starting any new diet, remember to ask your doctor if it’s a suitable option for you.