The influence of ingesting fish oil during two weeks of weight loss on changes in body mass and muscle strength

INTERVENTION: Participants were randomly assigned to either a fish oil or a placebo supplement in a juice‐based beverage form supplied by Smartfish Nutrition Ltd. The supplements were ingested for 6 weeks. The fish oil supplement contained 4g/day of omega‐3. After 4 weeks of supplementation, participants will undergo a 2‐week weight loss period. Measurements of body composition and muscle performance will be measured before supplementation, immediately before the weight loss and immediately after the 2‐week weight loss period. Participants were assigned to groups randomly using a list of 20 1 or 0 generated using the binomial distribution with probability 0.5 in Rstudio. Data was collected by Jordan Philpott either by computer output or by resistance machine output. Trial days and measurements Testing sessions commenced at 07:00 on wks 1 (day 7), 4 (day 27) and 6 (day 41) following an overnight fast and having consumed 500 ml of water 1‐2 h prior to arriving at the laboratory. Participants were instructed to empty their bladder before body weight was measured using standard laboratory scales (Seca Quadra 808, Birmingham, UK) with participants wearing underwear only. Body composition was measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry (iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare). All DXA scans followed procedures previously described by Rodriguez‐Sanchez & Galloway (2015) and were performed by the same trained technician (CV of body mass measurement = 1.95%, CV of LBM measurement = 1.6%, CV of fat mass measurement = 6.5%). Muscle strength and endurance The first test of muscle strength was a single leg isokinetic/eccentric maximum voluntary contraction (MVC) of the knee flexors using an isokinetic dynamometer. Participants were seated on the dynamometer with their upper body, hips and thigh securely strapped in CONDITION: Healthy volunteers ; Not Applicable INCLUSION CRITERIA: 1. Male aged 18 ‐ 35 years. 2. Resistance training for at least two times per week for 6 months prior to the study. 3. Healthy (no known metabolic diseases or eating disorders as determined by our health questionnaire). PRIMARY OUTCOME: ; Measured at weeks 1 (day 7), 4 (day 27) and 6 (day 41):; 1. Weight loss; 2. Body composition measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry (iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare); 3. Exercise performance during a two week period of energy restriction (60% of normal intake) measured using three exercises:; 3.1 Single leg isokinetic/eccentric maximum voluntary contraction (MVC) of the knee flexors using an isokinetic dynamometer; 3.2 Unilateral 1RM for leg extension and leg press on a fixed resistance machine; 3.3 Muscular endurance (as many repetitions as possible on leg extension and leg press exercises, with resistance set at 60% of individual baseline 1RM).; SECONDARY OUTCOME: ; Measured at weeks 1 (day 7), 4 (day 27) and 6 (day 41):; 1. Fat mass measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry ( iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare); 2. Fat‐free mass measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry (iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare); 3. Bone mass measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry (iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare); 4. Overall body fat percentage measured using a narrowed fan‐beamed dual‐energy x‐ray absorptiometry (iDXA GE Healthcare) with analysis performed using GE Encore 13.40.038 Software (GE Healthcare); 5. Resting energy expenditure measured using indirect calorimetry (Oxycon Pro; Cardinal Health); 6. Muscle anabolic signalling (the capacity for muscle to make new proteins) measured using western blot analysis; 7. Muscle catabolic signalling (the signals driving the breakdown of muscle proteins by the body) measured using western blot analysis; 8. mRNA expression (the expression of certain genes associated with muscle building and breakdown) during weight loss measured using western blot analysis.;