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  • Study protocol for a 9-month randomised controlled trial assessing the effects of almonds versus carbohydrate-rich snack foods on weight loss and weight maintenance

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Nutrition and metabolism
Protocol
Study protocol for a 9-month randomised controlled trial assessing the effects of almonds versus carbohydrate-rich snack foods on weight loss and weight maintenance
  1. Sharayah Carter1,2,
  2. Alison M Hill2,3,
  3. Catherine Yandell1,2,
  4. Jonathan D Buckley1,2,
  5. Sze-Yen Tan4,
  6. Geraint B Rogers5,6,
  7. Jessie Childs1,
  8. Mark Matheson1,
  9. Kate Lamb1,
  10. Susan Ward1,2,
  11. Tasha R Stanton1,7,8,
  12. Francois Fraysse1,2,
  13. Andrew P Hills9,
  14. Alison M Coates1,2
  1. 1Allied Health and Human Performance, University of South Australia, Adelaide, South Australia, Australia
  2. 2Alliance for Research in Exercise, Nutrition and Activity (ARENA), University of South Australia, Adelaide, South Australia, Australia
  3. 3Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
  4. 4Institute for Physical Activity and Nutrition (IPAN), Deakin University, Burwood, Victoria, Australia
  5. 5Microbiome Research, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
  6. 6College of Medicine and Public Health, Flinders University, Adelaide, South Australia, Australia
  7. 7IMPlementation And Clinical Translation (IIMPACT), University of South Australia, Adelaide, South Australia, Australia
  8. 8Neuroscience Research Australia, Sydney, New South Wales, Australia
  9. 9School of Health Sciences, College of Health and Medicine, University of Tasmania, Launceston, Tasmania, Australia
  1. Correspondence to Professor Alison M Coates; alison.coates{at}unisa.edu.au

Abstract

Introduction Epidemiological studies indicate an inverse association between nut consumption and body mass index (BMI). However, clinical trials evaluating the effects of nut consumption compared with a nut-free diet on adiposity have reported mixed findings with some studies reporting greater weight loss and others reporting no weight change. This paper describes the rationale and detailed protocol for a randomised controlled trial assessing whether the inclusion of almonds or carbohydrate-rich snacks in an otherwise nut-free energy-restricted diet will promote weight loss during 3 months of energy restriction and limit weight regain during 6 months of weight maintenance.

Methods and analysis One hundred and thirty-four adults aged 25–65 years with a BMI of 27.5–34.9 kg/m2 will be recruited and randomly allocated to either the almond-enriched diet (AED) (15% energy from almonds) or a nut-free control diet (NFD) (15% energy from carbohydrate-rich snack foods). Study snack foods will be provided. Weight loss will be achieved through a 30% energy restriction over 3 months, and weight maintenance will be encouraged for 6 months by increasing overall energy intake by ~120–180 kcal/day (~500-750kJ/day) as required. Food will be self-selected, based on recommendations from the study dietitian. Body composition, resting energy expenditure, total daily energy expenditure (via doubly labelled water), physical activity, appetite regulation, cardiometabolic health, gut microbiome, liver health, inflammatory factors, eating behaviours, mood and personality, functional mobility and pain, quality of life and sleep patterns will be measured throughout the 9-month trial. The effects of intervention on the outcome measures over time will be analysed using random effects mixed models, with treatment (AED or NFD) and time (baseline, 3 months and 9 months) being the between and within factors, respectively in the analysis.

Ethics and dissemination Ethics approval was obtained from the University of South Australia Human Research Ethics Committee (201436). Results from this trial will be disseminated through publication in peer-reviewed journals, national and international presentations.

Trial registration number Australian New Zealand Clinical Trials Registry (ACTRN12618001861246).

  • nutrition & dietetics
  • clinical physiology
  • public health
http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjopen-2019-036542

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    Footnotes

    • Contributors AMC, JDB, AMH, S-YT, GBR were coapplicants on the grant application and as such were involved with the original design. AMC was the lead applicant and is the principal investigator for the study. AMC, JDB, AMH, SC, CY are involved with study coordination and responsible for the day to day running of the trial, recruitment and sample collection. All authors (SC, AMH, CY, JDB, S-YT, GBR, JC, MM, KL, SW, TRS, FF, AH, AMC) contributed to method development and the writing and development of the protocol paper and all authors (as above) will have responsibility for analysis, statistical interpretation of outcomes and preparation of manuscripts for publication post-study completion.

    • Funding This work was funded by the Almond Board of California.

    • Disclaimer This funding source had no role in the design of this study and will have no role in the analysis or interpretation of the data.

    • Competing interests AMC has consulted for Nuts for Life (an initiative of the Australian Tree Nut Industry).

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

    • Patient consent for publication Not required.

    • Provenance and peer review Not commissioned; externally peer reviewed.