A ketogenic, or “keto,” diet is very low in carbohydrates, and the majority of the calories you eat come from fat. That makes it different from other low-carb plans that are focused on eating lots of protein.
Some people experience short-term weight loss on the keto diet, but this may be partly due to the release of stored water.
It’s unclear how effective keto is in the long term, and — as with all restrictive diets — there’s a good chance you’ll put the weight back on when you stop following it.
However, if you’re not working with a healthcare professional, the keto diet may come with health risks. And if you don’t carefully manage what you eat, you could also miss out on important nutrients, including fiber.
Before starting any diet, you should consider whether you actually need to lose weight. Work with a healthcare professional to find the weight range that is best for your health.
At ZOE, we don’t believe in restrictive diets that lead to rapid weight loss. They can make longer-term weight loss more difficult by changing your metabolism.
Our research shows there’s no “one-size-fits-all” solution for weight loss. With the personalized ZOE program, you can find the right foods for your weight and overall health goals.
You can take our free quiz to discover how ZOE can help you achieve your long-term goals. And read on to learn more about the keto diet.
How does the keto diet work?
The keto diet is often grouped together with other low-carb diets. While many of them are high-protein, keto is high-fat.
On the keto diet, your daily intake of calories is usually around 70%–80% fat, 10%–20% protein, and 5%–10% carbohydrate.
You can eat high-fat foods such as meat, full-fat dairy, and healthier fats like olive oil. Since carbs are very limited, starchy foods like potatoes, corn, peas, and lentils are excluded, along with all grains and all fruits, with the exception of occasional berries.
In theory, the keto diet works by switching your body from burning glucose to burning fat as its main fuel. Glucose is the primary fuel your body normally uses for energy. In a typical diet that contains 45–65% carbohydrate, most of that is glucose.
When there’s not enough glucose in your blood, your body starts to break down the fat you eat — and then your body fat — into chemicals called ketones, which it can use as an alternate fuel. This process is called ketosis.
Does the keto diet work for weight loss?
Some people report short-term weight loss on the keto diet, similar to many other popular diets. However, restrictive diets can be challenging to keep up long term, and many people put the weight back on.
As we’ll see below, there are also potential health risks from keto if you don’t pay close attention to the foods you choose.
Does keto work in the short term?
We’ve mentioned how the keto diet can help you burn fat by changing the fuel your body uses from glucose to ketones. But are the fast weight loss stories you hear about keto always due to its fat-burning abilities?
If you lose weight when you first start keto, some of it may come from losing water rather than fat. That’s because severely restricting carbs reduces the levels of a substance called glycogen in your muscles, the storage form of glucose.
Storing glycogen also involves storing water with it. If you start eating carbs again and replenishing your glycogen stores, the water weight will come back.
Other evidence of short-term fat loss on the keto diet is mixed.
In one study, people followed either a low-fat, plant-based diet or a low-carb, high-fat, animal-based diet for 2 weeks. The participants could eat as much or as little as they liked. They switched diets for the remaining 2 weeks.
People lost weight on both diets, but only the low-fat diet led to a significant loss in body fat. However, this was a small study of just 20 people who weren’t actively trying to lose weight.
A longer study found that people with obesity lost significant amounts of weight over the course of 24 weeks following a keto diet. The 83 participants also saw improvements to their cholesterol and blood sugar levels.
However, it’s important to note that physicians closely monitored the health of the study volunteers, who received food supplements to help them avoid nutritional deficiencies.
Does keto work in the long term?
As with any restrictive diet, it can be challenging to follow the keto diet in the long term. The reduced variety of foods and flavors may become less appetizing over time, and once people stop the diet, they usually put back on any weight they’ve lost.
Continuing with the keto diet long term may not be good for your health, either. A large review of other studies found that the evidence points to only short-term, but not long-term benefits of the keto diet.
One concern is that if you follow the basic principles of high fat and low carbs, you could end up eating a lot of saturated fat from foods like meat and high-fat dairy products.
A long-term diet high in saturated fat can increase your levels of unhealthy cholesterol (LDL), which is linked to a greater risk of heart disease.
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Keto also restricts some of the best sources of fiber, including starchy vegetables, legumes like lentils and chickpeas, fruits, and whole grains.
Eating plenty of fiber is crucial for the health of your gut microbiome, the trillions of microbes that live in your gut and help keep your body healthy.
Including fiber in your diet is linked to a lower risk of health problems like heart disease and diabetes and also to lower body weight.
Good sources of fiber that you can eat on the keto diet are non-starchy vegetables like bell peppers, zucchini, cauliflower, and broccoli. But most good sources of dietary fiber are restricted on the keto diet, as described above.
How to lose weight healthily
This effect may last for years to come and can make it more difficult to lose weight or keep it off.
At ZOE, we don’t believe in restrictive diets or losing weight too quickly. We know that the way your body responds to food is unique, and our studies show that not everyone responds well to high-fat diets.
With the ZOE program, you get personalized advice to help you find the best foods for your body. When you eat the right foods for you, your metabolism, weight, and overall health will benefit.
In fact, unpublished research from ZOE shows that when people closely followed our personalized nutrition program for 3 months, they lost an average of 9.4 pounds, while 82% had more energy and didn’t feel hungry.
The keto diet is a very low-carb, high-fat diet. It may lead to short-term weight loss for some people, but restrictive diets like keto can be difficult to stick to. Furthermore, many people regain any weight they’ve lost once they come off of it.
This may be partly because “crash” diets that lead to rapid initial weight loss can reduce your metabolic rate, making it harder to lose weight in the longer term.
If you do choose to go on the keto diet, it’s important to make careful food choices. Eating too much meat and high-fat dairy containing saturated fat could lead to health problems later on.
Fiber is really important for your gut microbiome, and it can be difficult to get enough of it on the keto diet. If you're going to try a keto diet, be sure to include non-starchy vegetables like bell peppers and cauliflower that contain plenty of fiber.
Restrictive diets can work against you in the long term. If you eat the right foods for your body, your overall health and your weight will benefit.
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The truth about fats: the good, the bad, and the in-between. (2019). https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good