Modified Ketogenic Diet in Amnestic Mild Cognitive Impairments

This study is an open-label, parallel-group randomized controlled clinical trial. The researchers hypothesized that a 12-week modified ketogenic diet (MKD) intervention in participants diagnosed with amnestic-mild cognitive impairments (aMCI) would improve cognitive functions and progression criteria compared to control groups.

The research sample will consist of individuals diagnosed with aMCI, and 36 volunteers, 12 individuals, were randomly assigned to three different research arms according to the block randomization method. To evaluate this sample size in the "repeated measures ANOVA" test of three independent groups with a medium effect size (f:0.30), 5% significance level (α), and 90% power (1-β) in the power analysis, the sample size should be at least 27 individuals has been calculated.

According to the dropout rate (25%) reported in similar ketogenic diet intervention studies in the literature, 36 was targeted as the sample size of the study.

For confidentiality purposes, the coding method will be used in the processing of data according to the study arms and the order of inclusion in the protocol (i.e., PC-1, AC-1, or KD-1, passive/active control, and the ketogenic diet, respectively). It is planned to evaluate cognitive functions with ADAS-Cog (Alzheimer's Disease Assessment Scale: Cognitive Subscale), physical performance with motor-cognitive dual-task and hand grip strength, and functional capacity with Lawton instrumental activities of daily living scale. Yesavage Geriatric Depression Scale-short form (GDS-15), which will also be used as an eligibility criterion, will be used to evaluate mood.

Intervention: After examining the food consumption diaries (7 days), diet planning will be made for the appropriate study arm (MIND or MKD). The daily energy of the diets is eucaloric in two diet groups, and daily energy will be determined according to the daily average energy intake determined by the nutritional status assessment of the individual and the ESPEN (European Society for Clinical Nutrition and Metabolism) consensus recommendation.

Ketogenic diet calculations will be made through the KetoDietCalculator program. The two basic principles of the planned modified ketogenic diet are 1) protein intake of 1 g/kg per day, and 2) a ketogenic diet ratio 1:1. According to the determined daily energy intake, the contribution of macronutrients to daily energy will be determined by the ketogenic diet ratio. Controlling protein intake per body weight is not a routine practice in ketogenic diet applications, and in this study - to preserve lean body mass as much as possible in elderly individuals - the ESPEN consensus recommendation will be taken into account in the calculations.

The MIND diet, which is the control group diet, will be planned following the 14 dietary guidelines defined elsewhere, and the above criteria will be applied in the same way in determining daily energy. MIND is a diet whose neuroprotective properties are currently accepted, with its ability to delay cognitive function loss and dementia supported by many population-based prospective studies.

Following the dietary training, both groups will be given brochures containing the basic principles and instructions of the diet and educational materials containing recipes developed specifically for the diet group. Compliance with the ketogenic diet is evaluated according to the individuals' serum ketone level (compliance criterion: β-hydroxybutyrate/BHB: 0.5-2.5 mmol/L) and food consumption diaries evaluated at 4, 8, and 12 weeks. Compliance with the MIND diet, which is the active control diet, will be evaluated with the MIND diet score calculated from weekly food consumption diaries (compliance criterion: MIND score >10/14).

In evaluating all outcome variables, the per-protocol analysis method will be applied to examine only participants who completed the research protocol. The intention-to-treat method will be used to evaluate some secondary outcome variables (i.e., biomarkers and anthropometry). Changes in primary and secondary outcome variables between the intervention and control groups during the study will be evaluated by repeated measures ANOVA test. All statistical tests will be evaluated in the SPSS (Statistical Package for Social Science) program at 90% power and 5% significance level.