*4.1. Study 1 Design*

This double-blind randomized placebo-controlled parallel design trial was approved by the University of Wollongong Human Research Ethics Committee (approval CT13/002), and prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12615001057572). Sixty-four participants were recruited, with all providing written informed consent. Exclusion criteria were <18 years of age and antibiotic use in the previous two months. Participants with an overweight or obese BMI (>25 kg/m2) were included in the study, with one participant of a BMI of 22 kg/m2. Participants were randomly assigned to three treatment groups of externally identical capsules: a placebo group,a2g dose of seaweed extract, anda4g dose of seaweed extract; participants and investigators were blinded to the treatment allocations. Two treatment doses were chosen to determine if there was a dose effect, as there were no previous data on humans. Randomization to treatment groups was determined using a computer-generated sequence and groups were assigned by someone independent from the study. The trial ran for a six-week period with sampling occurring at baseline and the end of week six. Participants were advised to maintain diet and exercise routines throughout the trial period and to continue to take any medications.
