JMIR Publications

ABSTRACT

Background:

The prevalence of obesity has increased substantially over recent decades and is associated with considerable health inequalities. Although the causes of obesity are complex, key drivers include over-consumption of highly palatable, energy-dense and nutrient-poor foods, which have a profound impact on the composition and function of the gut microbiome. Alterations to the microbiome may play a critical role in obesity by affecting energy extraction from food and subsequent energy metabolism and fat storage.

Objective:

We report the study protocol and recruitment strategy of the PROMISE (PRedictors linking Obesity and the gut MIcrobiomE) study, which characterises the gut microbiome in two populations with markedly different metabolic disease risk (Pacific and European women) and different body fat profiles (normal and obese). It investigates: (1) the role of gut microbiome composition and functionality in obesity and body fat distribution; and (2) the interactions between dietary intake, eating behaviour, sweet, fat and bitter taste perception, sleep and physical activity, and their impact on the gut microbiome, metabolic and endocrine regulation and body fat profiles.

Methods:

Healthy Pacific and New Zealand (NZ) European women aged between 18 - 45 years from the Auckland region were recruited for this cross-sectional study. Participants were recruited such that half in each group had either a normal weight (BMI 18.5-24.9 kg/m2) or were obese (BMI ≥30 kg/m2). In addition to anthropometric measurements and assessment of the body fat content using dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA), participants completed sweet, fat and bitter taste perception tests, food records and sleep diaries, and they wore an accelerometer to assess physical activity and sleep. Fasting blood samples were analysed for metabolic biomarkers and endocrine regulators and DNA extracted from faecal samples were analysed by shotgun sequencing on an Illumina HiSeq2500 instrument. Participants completed questionnaires on dietary intake (e.g. 5-day food diaries, food frequency, dietary diversity), eating behaviour (three-factor eating questionnaire), sleep (e.g. sleep quality, chronotype), and physical activity. Data were analysed using descriptive and multivariate regression methods to assess the associations between dietary intake, taste perception, sleep, physical activity, gut microbiome complexity and functionality, and host metabolic and body fat profiles.

Results:

Of the initial 351 women enrolled, 142 Pacific women and 162 NZ European women completed the study protocol. A partnership with a Pacific primary health and social services provider facilitated the recruitment of Pacific women, involving direct contact methods, word-of-mouth and networking within the Pacific communities. NZ European women were primarily recruited through online methods and special interest Facebook pages.

Conclusions:

This cross-sectional study will provide a wealth of data enabling the identification of distinct roles for diet, taste perception, sleep and physical activity in women with different body fat profiles in modifying the gut microbiome and its impact on obesity and metabolic health. It will likely advance our understanding of the aetiology of obesity and will guide future intervention studies involving specific dietary approaches and microbiota-based therapies. Clinical Trial: This trial is registered at www.anzctr.org.au as ACTRN12618000432213.