- A ketogenic (keto) diet outperformed a Mediterranean diet in improving metabolic health metrics in a new, very small study in people who had recently received a diabetes diagnosis.
- The study found that a keto diet improved blood sugar, gut microbiota composition, body mass index (BMI), and waist circumference more than a Mediterranean diet.
- The keto diet has proven to be successful for weight loss, but has been associated with numerous adverse effects. It involves a radical reduction in carbohydrates, and changes the way the body accesses energy.
- The advantages the keto diet exhibited over the Mediterranean diet were not long-lasting in the year-long study, fading after 6 months.
Compared to a Mediterranean diet, a ketogenic (keto) diet produced more immediate beneficial changes in people with type 2 diabetes during a 12-month study.
However, the keto diet’s relative advantages appeared to wane beyond 6 months. The diets resulted in similar improvements in participants’ Health by the end of the study.
The small study, conducted by researchers in Italy and Brazil, and whose findings appeared in the journal Metabolites, recorded short-term improvements in gut microbial diversity, various anthropometric measures, and metabolic indicators.
The keto diet is a weight-loss diet based on the principle that by dramatically limiting the presence of carbohydrates (sugars) available to the body, the body will instead burn away fat for energy. The diet can produce significant weight loss and has been linked to other benefits.
However, the keto diet has also been associated with various serious adverse effects, especially with long-term use, making it difficult to safely study in human subjects.
The Mediterranean diet takes a less radical approach to dieting, emphasizing a balanced approach to nutrition and lifestyle.
Participants in the study were people aged 45 to 65 with obesity who had recently been received a type 2 diabetes diagnosis.
They had not yet begun taking any medication for the condition. At the start of the study, there were 11 participants. By the halfway point, 10 remained, and eight people completed the full year-long trial.
The individuals had been randomly assigned either to a very low-calorie ketogenic diet or to a Mediterranean-type diet. Those in the low-calorie keto group were supplied protein-based meals containing few carbohydrates — less than 30 grams (g) per day.
After 2 months, people in the low-calorie keto group were gradually transitioned to the Mediterranean diet to avoid keto-diet safety issues.
From month 4 onward, both groups followed an Mediterranean diet for the remainder of the study.
At the start of the study and throughout the year, the researchers took stool samples from participants and used next-generation genetic sequencing to identify the microbiota they contained.
They also took anthropometric measurements — such as body mass index (BMI) and waist circumference — and measured key metabolic values such as hemoglobin A1C (HbA1c), a key indicator of blood sugar, and triglycerides, a marker of cholesterol.
At month 6, those in the low-calorie keto group exhibited significant improvements beyond the Mediterranean diet group in HbA1c levels, BMI, waist circumference, and beneficial gut bacteria.
Among the low-calorie keto group’s enhanced gut bacteria was the Akkermansia species, which is involved in metabolic Health and gut barrier protection.
After 6 months, however, most of these indicators of health improvement receded, though they never fell back to where participants were at the start of the study, leaving the researchers encouraged about keto.
“The keto diet can have risks such as nutrient deficiencies, liver issues, constipation, and kidney issues,” explained Jason Ng, MD, BA, of the Department of Medicine at the University of Pittsburgh, an expert in endocrinology and metabolism, explained to Medical News Today.
“Nutrient deficiencies can occur from not eating a variety of vegetables and grains that may have nutrients. Liver and kidney issues can occur because of the high demand for metabolizing fat and proteins that can overload those organs. Constipation occurs from not eating fibrous foods that can keep bowel movements regular. Mood swings and difficulty thinking can occur sometimes when your brain is deprived of sugar,” added Ng, who was not involved in the current study.
Michelle Routhenstein, MS, RD, CDCES, CDN, founder of, and preventive cardiology dietitian and heart health expert at EntirelyNourished, also not involved in the current research, also told MNT:
“In my private practice, I frequently see patients who have tried the keto diet and are dealing with increased blood sugar, inflammation, elevated blood pressure, and worsening lipid profiles.”
Commenting on the results of the study, Ng told us he remained cautious for the moment.
“Potential weight loss and possible improvement in gut microbiota from keto diets may be possible in carefully selected patients who are Healthy otherwise, and with close monitoring to ensure minimization of those side effects,” he noted.
For those with type 2 diabetes, in particular, he agreed that “a keto diet may be a valuable tool in the management of obesity and improvement in insulin resistance in patients […] who cannot lose weight or have variable sugar control.”
However, Routhenstein did not “ recommend a keto diet for individuals with type 2 diabetes, as the condition already heightens the risk of heart disease.”
Both framed a Mediterranean diet as a safer bet.
“A Mediterranean diet,” noted Ng, “is a valuable resource and tool to help people with [type 2 diabetes] control their sugars, improve weight loss, and is likely easier to maintain than a keto diet, and is an established diet that can improve the Health of patients with [this conditon].”
“Rather than following fad diets,” Routhenstein advised, “I recommend focusing on nutrient adequacy, effective meal planning, and a balanced approach that includes proper timing for meals. This strategy is more sustainable for managing type 2 diabetes and improving overall health.”
