Adherence to Ketogenic and Mediterranean Study Diets in a Crossover Trial: The Keto–Med Randomized Trial

Abstract

Adherence is a critical factor to consider when interpreting study results from randomized clinical trials (RCTs) comparing one diet to another, but it is frequently not reported by researchers. The purpose of this secondary analysis of the Keto–Med randomized trial was to provide a detailed examination and comparison of the adherence to the two study diets (Well Formulated Ketogenic Diet (WFKD) and Mediterranean Plus (Med-Plus)) under the two conditions: all food being provided (delivered) and all food being obtained by individual participants (self-provided). Diet was assessed at six time points including baseline (x1), week 4 of each phase when participants were receiving food deliveries (x2), week 12 of each phase when participants were preparing and providing food on their own (x2), and 12 weeks after participants completed both diet phases and were free to choose their own diet pattern (x1). The adherence scores for WFKD and Med-Plus were developed specifically for this study. Average adherence to the two diet patterns was very similar during both on-study time points of the intervention. Throughout the study, a wide range of adherence was observed among participants—for both diet types and during both the delivery phase and self-provided phase. Insight from this assessment of adherence may aid other researchers when answering the important question of how to improve behavioral adherence during dietary trials. This study is registered at clinicaltrials.gov NCT03810378.

Findings from Diet Comparison Difficult to Interpret in the Absence of Adherence Assessment. Comment on Tricò et al. Effects of Low-Carbohydrate versus Mediterranean Diets on Weight Loss, Glucose Metabolism, Insulin Kinetics and β-Cell Function in Morbidly Obese Individuals. Nutrients 2021, 13, 1345

“…The practical implications for motivating food factors and values within interventions has been recently examined by Eustis and colleagues [7]. In our own trials, we have found varying psychosocial, demographic, and environmental motivational factors regarding adherence to study diets [6,8,9].…”

“…Greater dietary adherence, regardless of the type of diet, is an important factor in weight-loss success and maintenance [3][4][5]. We recently conducted an intervention trial comparing a lowcarbohydrate (ketogenic) and a Mediterranean diet in which we published a separate methods and adherence paper [6]. Even when we were providing participants with a food delivery service for 4 weeks to maximize adherence to their research diets we observed a wide range of adherence variability among participants; overall adherence was shown to be similar, increasing internal validity.…”

Case Report: Ketogenic Diet Is Associated With Improvements in Chronic Obstructive Pulmonary Disease

“…Furthermore, dietary interventions may be more acceptable to patients than long-term drug therapies, which have poor adherence in COPD ( 27 ). Conversely, despite the common conception that KD are not sustainable for patients, trials show that patients given adequate education and support adhere to and enjoy KD as much as other diets and standard of care ( 8 , 28 ).…”

Ketogenic diet ameliorates lipid dysregulation in type 2 diabetic mice by downregulating hepatic pescadillo 1

“…In addition, emerging evidence from long-term KD intervention in humans supports that the ketone level was also attenuated in T2DM patients (Landry et al 2021 ). And the initial β-HB value was below ketosis level at the beginning of the KD treatment (0.12 mmol/L), then peaked at 1.1 mmol/L (4 weeks) and decreased to 0.51 mmol/L by week 12 in the end (Landry et al 2021 ). Moreover, β-HB levels are significantly different among different mice by KD intervention based on previous reports.…”