Interactive Effects of an Isocaloric High-protein Diet and Resistance Exercise in Untrained Overweight Young Men

Background: The interactive effects of resistance training and dietary protein on hormonal responses in overweight or obese adults are not clear and remain controversial. Investigators tested the effect of an isocaloric high-protein diet on body composition, ghrelin, and metabolic and hormonal parameters during a 12-week resistance training program in untrained overweight healthy young men.

Methodology: Investigators randomized 18 healthy young males to a standard diet (ST group) or an isocaloric high protein diet (HP group). They have not participated in any weight-management program during the previous 6 months. An open-label design will be used. At enrolment, participants will randomly assign to one of two groups: a control group with a standard diet (total calories 2,400 kcal/day, 60% carbohydrate, 15% protein and 25% fat; ST group) and an interventional group with an isocaloric high protein diet (total calories 2,400 kcal/day, 55% carbohydrate, 30% protein and 15% fat; HP group). Participants in both groups take part in a scheduled resistance exercise training program. Participants does not take part in any other resistance training program or competitive sport over the study duration. At the start of the study, participants will be instructed to maintain their assigned diet throughout the study period. This will be assessed using a food frequency questionnaire (FFQ) with a 24-h recall after 12 weeks. Participants are presented with two-dimensional food pictures of the actual size of portions on a computer by a single trained dietitian to minimize interviewer bias. Medium are defined as the portion sizes shown, small are approximately half the medium portion size, and large are one-and-a-half times the medium portion size.

Exercise Protocol All participants will be under supervision during participation in the progressive supervised resistance exercise-training program. They participate in an onsite supervised protocol for 12 weeks (6 days per week). Exercise duration will be increased gradually, from 50 min at week 1 to 80 min at week 12, including warm-up for 20 min and cool-down periods for 10 min by carrying out gentle stretching exercises of the upper and lower limbs. A one repetition maximum (1-RM) is the maximum weight that can be lifted for one complete repetition of the movement. For each participant, the RM will be calculated for a particular muscle group. Each movement will be carried out at 60-80% of his 1-RM. Resistance will be increased slowly by three steps; step 1 (60-70% of his 1-RM for week 1-4), step 2 (65-75% of his 1-RM for week 5-8) and step 3 (70-80% of his 1-RM for week 9-12).

Baseline and Follow-up Measurements Height and bodyweight are measured using a digital scale with the examinee wearing a light gown, but no shoes. Body mass index (BMI) are calculated as weight (kg) divided by height squared (m2). The percentage body fat and total fat mass are measured by bioelectric impedance analysis (Inbody 3.0; Biospace Co., Ltd., Seoul, Korea), a sensitive test for quantification of changes in lean and fat mass in vivo and for assessment of regional fat distribution. A mercury sphygmomanometer are used for measurement of blood pressure (BP) of each participant, in the sitting position, after a 10-min resting period. Two readings each for the systolic and diastolic Bps are recorded at 3-min intervals, and the average of each measurement are included in our analysis.

Blood samples are obtained preprandially at 0.800 hours from each participant's antecubital vein after a 12-h fast, and are used for determination of plasma glucose, insulin, lipid profile, total ghrelin, GH, insulin-like growth factor-1 (IGF-1), testosterone and cortisol. Blood samples are obtained at baseline (prerandomization) and 12 weeks after randomization.