Effects of low salt weight loss diets on the way blood vessels work

This is a randomized controlled cross over study. Participants will be randomised into two equal groups matched for body mass index (BMI), sex, age. One group (1) will start with an energy restricted diet using meal replacement low in sodium (meal replacement will be provided for breakfast, lunch and dinner) for 8 weeks followed by a 2 week weight maintenance period on a normal salt diet and finish with a control period of 8 weeks following their normal pre study diet. The second group (2) will start by following their usual diet for 8 weeks followed by 8 weeks weight loss (as above) finishing with 2 weeks weight maintenance. This study will last for a total of 18 weeks. Participants will be asked to attend maximum 8 appointments at the University of South Australia. The duration of the visits will vary between 15 minutes and 1.5 hours (visits where all measurements are taken will last approximately 1.5 hours (baseline, after 8 weeks weight loss/ control period and after the 2 weeks weight stable period) visits during the weight loss period will last approximately 15 minutes). In the weight loss period participants will attend the University clinic every two weeks to be weighed and to collect meal replacement for the next 2 week period (duration of visit approximately 15 minutes). In the control period participants will be asked to attend the University clinic after 8 weeks (duration approximately 1.5 hours). In this period they will be continuing on their usual diet. To assess food habits a food frequency questionnaire (FFQ) will be completed a t baseline. 3 day diet diaries will be completed at baseline, after 8 weeks weight loss/control period and after the 2 week weight stable period. As a compliance measure weight loss and amount of meal replacement sachets used will be measured. Participants will be asked to return all used and unused meal replacement sachets to be counted.