The Study

Moreno et al. (2014) studied the effects of a very low-calorie ketogenic diet (KD) in comparison with the standard low-calorie diet in the treatment of obesity. As obesity is now an epidemic in industrial countries threatening the public health and that pharmacological and lifestyle changes usually failed, it is important to find new simple ways to combat this epidemic.


A total of 79 patients were enrolled in the Obesity Unit of a Madrid (Spain) hospital. They were healthy adult individuals presenting only obesity and pre-diabetes, without any other preexistent medical conditions. They had a stable weight for at least 3 months, a desire to lose weight and a history of failed attempts to lose weight using a diet. However, patients who tried to lose weight using diet or pills in the past 6 months were excluded from the study, as well as women who were pregnant, breastfeeding or willing to become pregnant.

The group was then randomly assigned to a KD or a standard low-calorie diet. The KD group followed a diet with three successive stages: active, reeducation and maintenance. Furthermore, they use a commercially available protein mix containing 15g of protein, 4g of carbohydrates and 3g of fats providing 90-100 kcal. During the active stage, subjects had the actual KD (600-800 kcal/day) with the calculated amount of protein mix according to their body weight plus 50g or less of carbohydrates from vegetables, 10g of fats from olive oil, and supplements of vitamins and minerals. After that, protein mix was gradually substituted by two servings of meat or fish per day. This phase lasted between 30 and 45 days depending on the individual. During the reeducation phase, the patients had a low-calorie diet (800-1500 kcal/day) with progressive reintroduction of different foods. Finally, in the maintenance phase, patients had a balanced diet consisting a 1500-2250 kcal/day. On the other hand, the other group had a constant low-calorie diet (45-55% carbohydrates, 25-35% fats, and 15-25% protein plus 20-40g/day of fiber) throughout the duration of the study with a calorie value of 10% below the calculated energy expenditure for each particular individual corresponding to 1400-1800 kcal/day.

Interventions during the one-year program period included group meetings, formal exercise program recommendations and assessments by dietician and physician. They took place after 2 weeks, 2 months, and every 2 months after that up to one year. A phone line was also put in place to answer all the questions and encourage patients throughout the process.


Among the 79 patients enrolled at the beginning of the study, 53 completed the one-year program and were included in the study, a dropout rate comparable to other studies involving obese patients. It is interesting to note that, among the patients who had completed the program, 88.6% were women. The KD group had a quicker and more pronounced weight loss than the standard low-calorie diet group. After one year, the KD induced a weight loss of 10 kg (22lb) more than the one induced by the standard low-calorie diet. Furthermore, over one year, 88.9% of the patients following the KD lost more than 10% of their initial weight, compared with only 34.6% of the patients following the standard low-calorie diet. The decrease in other obesity parameters, such as BMI, waist circumference and fat mass, was also more pronounced in the KD group. The KD also induced beneficial sustainable changes in many biological parameters, such as blood glucose level, total cholesterol and markers of kidney functions.

KD induced more side effects than the standard low-calorie diet, including weakness, fatigue, headache, muscle weakness, constipation, high level of blood uric acid and nausea. However, these side effects were generally mild and disappeared after the first weeks. As such, these side effects were not considered as a factor contributing to the dropout of certain patients.


The KD was significantly superior in the induction of weight loss compared with a standard low-calorie diet, with only transient mild side effects. “Furthermore, the results at one year after starting the treatment showing that most of the patients still maintain a weight reduction higher than 10% of the initial weight and that lean mass was preserved.

Study Editor

Marie-Christine Brotherton holds a Ph.D. in Cellular and Molecular Biology with specific expertise in Parasitology, Proteomics, Drug Resistance and Genomics. She also holds a MBA with a major in Corporate Social and Environmental Responsibility. She has strong experience with the scientific publication process, including author guidelines requirements, as well as with the medical and social/environmental fields. She can be reached by email at


Moreno, B., Bellido, D., Sajoux, I., Goday, A., Saavedra, D., Crujeiras, A. B., & Casanueva, F. F. (2014). Comparison of a very low-calorie-ketogenic diet with a standard low-calorie diet in the treatment of obesity. Endocrine47(3), 793-805.