When put on a very-low-calorie ketogenic diet, weight loss comes from mostly fat and does not negatively affect metabolism, researchers found.
April 19, 2018
Can you really lose weight quickly and keep it off? Experts have long believed it’s impossible, but a recent study out of Spain suggests that a version of the ketogenic diet may do just that.
In a small study, published in February 2018 in the journal Nutrition and Metabolism, 12 obese people followed an adjusted version of the popular ketogenic diet that was very low in calories for about two to three months, and lost about 45 pounds each — and kept the weight off even after increasing their calorie intake one to two months later.
The likely reason they were able to keep the weight off, researchers say, is their resting metabolic rate (RMR) was maintained, and they retained their lean muscle mass. RMR is a measure of metabolism (meaning how your body uses energy), while immobile, and it plays an important role in sustaining weight loss, according to other research, published in August 2016 in the journal Obesity.
“[This study] does support other existing research findings that you can indeed lose weight on a ketogenic-inducing diet, and higher levels of protein intake, while following a calorie-restricted diet does help preserve the loss of lean muscle mass,” says Lona Sandon, PhD, RDN, assistant professor in the department of clinical nutrition at the University of Texas Southwestern Medical Center in Dallas.
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Why Increasing Protein Intake to Induce Ketosis Helped Participants Maintain Lean Muscle Mass
In the study, About 81 percent of participants’ weight loss came from fat loss, which was made possible through the main mechanism of any ketogenic diet: ketosis, a metabolic state through which the body turns to burning fat or protein rather than carbs for energy.
The classic ketogenic, or “keto,” diet calls for consuming a low amount of carbs, a high amount of fat, and a moderate amount of protein. But in the current study, participants induced ketosis by getting the majority of their calories from protein, a small amount from fat, and a low amount from carbs. One of the side effects of very low-calorie diets is loss of lean muscle mass, but on the adjusted keto diet in the study, participants preserved lean muscle mass. Researchers attributed the preservation of lean muscle mass to participants’ sustained RMR, and their results support those of a prior study, published in February 2017 in the Journal of Clinical Endocrinology and Metabolism.
A Closer Look at How Researchers Drew Their Findings on the Adjusted Ketogenic Diet
Before researchers accepted participants into the 2018 study, they screened them for health issues, like diabetes, that could have affected the study results or excluded them from safely following the program.
Twenty participants were tasked with following a very-low-calorie keto (VLCK) diet consisting of 600 to 800 calories. They took supplemental docosahexaenoic acid (DHA) omega-3 fats, vitamins, and minerals. DHA is an important structural component of the human brain, which was added to participants’ diets to ensure their body had enough of the component during fat loss. They took vitamins and minerals to make up for the nutrients lost from carb-containing foods. Meanwhile, they also followed a “formal exercise program.” The program was not defined in the study paper, and the study authors were not available for comment by this story’s publication.
Participants met with researchers 10 times over a four-month period. During 4 of the 10 visits, researchers analyzed participants’ blood and body fat for changes in body weight, hormones, ketone bodies (which are produced during ketosis), and muscle losses. After 60 to 90 days, participants were gradually taken off ketosis and placed on a low-calorie diet consisting of between 800 and 1,500 calories per day, and then a maintenance diet consisting of 1,500 and 2,000 calories, depending on the participant. Out of the 20 participants enrolled in the study, 12 completed the regimen and lost about 44.5 pounds each.
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What the Study Results Suggest if You’re Considering the Ketogenic Diet
Dr. Sandon says this diet regimen is typically very challenging for people to stick with and ultimately unrealistic to follow in a real-world setting, adding that the small study group furthermore hurts the credibility of the findings.
Katherine Arvesen, RDN, who in private practice in Plano, Texas, also notes that the study was not randomized and controlled, which is the gold standard for medical research to minimize error and bias. In this study, the patients were their own controls, meaning their results were compared with their own baseline (starting) measurements, not with the results of a control group.
Ideally, Arvesen says this study would have a control group following the same calorie limit with typical intake percentages of fat, protein, and carbohydrates. Arvesen also cautions the sample size of the study was small, and the study duration was relatively short, possibly reducing credibility of the findings further.
Experts agree more research needs to be done to determine which keto diet has the potential to preserve muscle and help increase the chances of sustained weight loss. But similar studies suggest the keto version analyzed in this study may hold promise. For example, a randomized study published in December 2014 in the journal Endocrinefound that a very-low-calorie ketogenic diet was more effective at sustaining weight loss and preserving lean muscle mass in obese people than a standard low-calorie diet after one year.
Regardless of its efficacy for weight loss, the ketogenic diet can result in side effects that many people may find unbearable. Commonly described as “the keto flu,” those side effects include fatigue, dehydration, and headaches.
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“I would not recommend it for type 1 diabetics or for type 2 diabetics who are taking medication to lower their blood sugar,” says Sandon. She adds that this may be an appropriate approach for individuals who need to lose excess body fat quickly, but only in the short term. Long-term risks of following keto include nutrient deficiencies.
Ultimately, if you’re considering keto, medical support may be the key to your success. Both Sandon and Arvesen recommend a consultation with a registered dietitian nutritionist upon approval from your physician before making major changes in your diet. If you don’t have one, you can find one at EatRight.org.