What Is Ketosis, and Is It Really the Key to Lasting Weight Loss?

You’ve probably heard (a lot) about the ketogenic (or “keto”) diet—a low carb, high fat diet similar to the Atkins and other low carb diets. This buzzy diet involves drastically reducing carbohydrate intake and replacing it with fat, with the intention of spiking the body’s fat-burning efficiency.

This metabolic state is called ketosis: when the body burns fat for energy instead of relying on the sugar (glucose) that comes from carbohydrates like grains, fruits, and legumes. More specifically, ketosis involves the creation of ketones by the liver. Ketones are a kind of alternative for the body, created by the liver when glucose is in short supply. 

Therein lies the dramatic potential for weight loss: when you deprive the body of glucose to use as fuel, it will turn to fat instead, burning it up instead of stashing it away in the belly, booty, or elsewhere. Makes perfect sense, right? 

The ketogenic diet, and its capacity to “force” the body into a hyper-fat-burning state, has been hailed by the carb-opposed for years, but is ketosis the trick to lasting weight loss? And is it safe? Let’s find out. 

Has Ketosis Been Clinically Studied?

A 2013 meta-analysis of 13 studies of ultra-low-carb diets found that participants who entered ketosis achieved greater long-term weight loss than by following a low-fat diet. Additionally, the keto dieters lost an average of 2 pounds more than the low-fat dieters. The study also reported a decrease in diastolic blood pressure and triglyceride levels for keto dieters.

Another study from 2020 of 34 older, obese adults found that entering ketosis for 8 weeks allowed them to lose three times as much total body fat as those who followed a low-fat diet. Reduced blood sugar and improved insulin sensitivity were also reported, suggesting significant health benefits for those with type 2 diabetes or prediabetes.

Sounds Great, But Before You Rush In…

Burning fat certainly does seem like an efficient way to drop pounds, but bullying the liver into producing ketones isn’t so simple. There are some important factors you need to keep in mind about ketosis:

To enter and stay in ketosis, a typical adult must consume less than 50 grams of net carbohydrates per day (measured as total carbs minus fiber). Depending on your level of ambition (or discipline), a daily intake of 20–50 net carbs is typical. As a frame of reference, a thick slice of bread contains 21 grams of carbohydrates, a medium apple 25.It usually takes 2-4 days to reach a state of ketosis, but some people may need a week or longer. This depends on a variety of factors, such as activity level and pre-existing diet. For example, an athlete will likely reach ketosis faster than an inactive person, and a person transitioning off a high-carb diet will take longer.Eating too much protein can interfere with ketosis, as protein can be converted into glucose if consumed in high amounts, which can slow the transition into ketosis.

Does Ketosis Have Side Effects?

When you stop eating carbohydrates—which do contain essential nutrients—altogether it can be enough of a shock to the body to cause an immune system reaction. The “keto flu” is usually experienced during the first week of entering ketosis and is usually over within a few days.

According to WebMD, temporary side effects can include:

Constipation (from reduced fiber intake)Stomach ache or nauseaHeadacheFatigueBrain fogIrritabilityTrouble SleepingCrampsBad breath (also known as ketosis breath)Sore musclesSugar cravings

Ketosis can also change your body’s water and mineral balance, so adding extra salt to your meals, taking mineral supplements and drinking more water can help ease symptoms.

Are There Risks to Ketosis?

According to Healthline, staying in ketosis for long periods can have the following risks: 

Excess fat in the liver: With so much fat to metabolize, the diet could make any existing liver conditions worse.Kidney stones Low protein in the bloodMicronutrient deficiencies: Cutting out a range of fruits, grains, and vegetables can cost the dieter valuable selenium, magnesium, vitamins B, C, and more.

It’s important to talk to your doctor about your nutritional needs before embarking on a ketogenic diet, particularly if you have a medical condition.

A review by the National Lipid Association urges people with lipid disorders (such as high cholesterol or triglycerides), a history of kidney and liver disease, heart failure, atherosclerotic cardiovascular disease, and people on blood thinners to be cautious when considering ketosis.

For nursing mothers who are already low on fluids and burning extra calories, ketosis can pose risks for both baby and mother, including a dangerous state of ketoacidosis. Doctors recommend holding off on ketogenic diets until after they are done breastfeeding.

For those with type 2 diabetes, the medication sodium-glucose cotransporter 2 (SGLT2) inhibitors can increase the risk of diabetic ketoacidosis, a dangerous condition that increases blood acidity. This creates a precarious metabolic state that could easily be aggravated by intentional ketosis and should be avoided.

Is Ketosis Effective (and Safe) for Weight Management in the Long-Term?

Although entering a state of ketosis appears to deliver fast results, the first few pounds that you lose will most likely be water weight. And no matter what diet you’re on, you can gain weight on any eating plan if you are consuming 4,000 calories a day. Don’t expect that entering ketosis will change the mechanics of your metabolism to the point where calories don’t matter.

And there is still research being done on its long-term effects, however, there is little difference reported between the long-term effects of a keto diet and a higher carbohydrate diet. 

“This is a very restrictive diet that’s tough to follow. … Because the saturated fat content is high, coupled with limited amounts of fruits, vegetables, and whole grains, it is not optimal for health.”

Jason Ewoldt, RDN, LD • Mayo Clinic Healthy Living Program

According to Jason Ewoldt, RDN, LD, a wellness dietitian at Mayo Clinic Healthy Living Program, ketogenic diets are less than ideal for long-term commitment. “This is a very restrictive diet that’s tough to follow. The average person is not going to keep doing this long term. Also, because the saturated fat content is high, coupled with limited amounts of fruits, vegetables and whole grains, it is not optimal for health.”

It can be a confusing decision to make, especially as there is no real evidence of its sustainability. And there are many other methods that can achieve the same benefits for weight loss and improve health conditions like diabetes without having to cut out so many foods. At the end of the day, you have to evaluate what is sustainable for you in the long run and we suggest consulting with a dietician to see if entering ketosis makes sense for you.

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