Franny Jongbloed

184 CHAPTER 7 Dietary intervention All dietary interventions lasted for five consecutive days and were given in an outpatient setting. For the kidney donors, the diet was initiated six days prior to surgery. For the morbidly obese patients, the diet started between several weeks to five days prior to the surgery date. After providing written informed consent, patients were randomized into one of three groups. During the study, patients were offered a contact person whom they were able to approach with an accessibility of 24 hours per day with questions regarding the diet, which they frequently did. Directly after completion of the diet, patients visited the outpatient clinic to evaluate their experience, and to donate a venous blood sample. The first group received a 30% DR and 80% PR restricted diet. This synthetic liquid diet containing an estimated 70% of the individual’s required calories and 20% of the individual’s protein, based on the basal metabolic rates and on the daily energy requirements (DER) as calculated with the Harris–Benedict formula 29 . The Harris–Benedict formula takes into account gender, height, age, body weight and estimated activity level. This formula is validated up to a BMI of 40. Whenever an individual had a BMI >40, the body weight corresponding to a BMI of 40 was used to calculate the DER. Normal protein intake was set at 15% of the total calories based on the DER. Participants received calorie- and protein-restricted powder shakes (Scandishake® Mix, Nutricia Advanced Medical Nutrition, The Netherlands) as the main component of the diet. The shake was provided as a powder consisting of 4% protein, 53% carbohydrates and 43% fat, and was diluted with water. The main protein source was casein with a limited amount of whey protein (Table S2). The shakes were combined with a limited number of protein-restricted products (mainly fruits and vegetables) until the desired individual diet was reached. These protein-restricted products included: all fruits except bananas, all vegetables in a limited amount of 200 g per day with the exception of asparagus, and a maximum of one piece of gingerbread per day. The second group received a synthetic diet that was isocaloric to each individual’s DER (termed the DER-diet), which was also calculated using the Harris–Benedict formula 20 . The DER-diet was offered as a shake (Nutridrink® Compact, Nutricia Advanced Medical Nutrition, The Netherlands) and was consumed without further dilution. This shake consisted of 16% protein, 49% carbohydrates and 35% fat (Table S2). A limited number of protein-restricted products as offered to the restricted diet group, was added until the individual’s DER was reached and average protein intake was an estimated 15% of all calories. All participants, randomized to either the restricted diet or the DER-diet, were blinded to which diet they received. The third group did not receive a synthetic diet or a dietary intervention. This group continued their usual daily eating pattern. Patients were asked to keep a diet diary during the period in which patients in the other two groups received the synthetic diet. Using this diary, their daily nutritional intake was measured and calculated for five days, resulting in mean overall