An investigation into the effect of a 12-week RCT comparing a low carbohydrate, high fat diet vs mainstream nutrition guidelines on metabolic health outcomes in overweight New Zealand Defence Force personnel.

Title: A 12-week RCT to assess the efficacy of a low carbohydrate, high fat diet compared with mainstream nutrition guided diet (i.e. high carbohydrate, low fat) on weight loss and metabolic health outcomes (glycaemic control; lipid markers) in a group of 41 overweight New Zealand defence force personnel. Once assessed for eligibility, participants were randomly assigned to the two dietary groups. They attended a 90 minute face-to-face workshop delivered by a Registered Nutritionist who was part of the research team) detailing the dietary approach (or both styles of eating. They were also provided with supporting resources. For the mainstream group, this included the Ministry of Health website on food & Nutrition guidelines as well as the associated hard copy guidelines booklets. The LCHF group were directed to a designated website the team created specifically for this research project as well as a hard copy booklet, again created for the purpose of this research work. Participants were not prescribed with a personalised set of a energy and macronutrient requirements, but rather they were provided will general guidelines about concepts and foods to consume and to avoid on their respective diet. It was anticipated that the mainstream style of eating (Usual Care) reflected a macronutrient profile that aligned with the New Zealand Food & Nutrition Guidelines (i.e. Carbohydrate: 45-60% of total energy; Protein 15-25% of total energy; Fat 30-33% of total energy). It was anticipated that the LCHF style of eating reflected a carbohydrate intake approximating less than the lower range of Usual Care recommendation i.e., <45% of total energy; a higher fat intake, approximating more than 33% of total energy, and a moderate protein intake, approximating 15-25% of total energy. A telephone support line was available throughout the 12 weeks for the participants to access should they have needed to. All measurements were conducted at the naval base during work hours. A full set of outcomes (i.e. weight, waist circumference and a blood assay to assess lipids and glycaemic control) were measured at weeks 0 (prior to the start of the intervention) and at week 12. At weeks 4 and 8, a weight and waist measure were recorded for monitoring and support purposes. To assess adherence, participants were asked to complete a 4-day food diary to be discussed at these meetings for discussion. At the meetings themselves, they were asked to rate their level of adherence on a 10-point scale. This was used as a monitoring and discussion point at these sessions. During this time, participants had the opportunity to discuss their progress or queries they have with the team.