Predictors Linking Obesity and the Gut Microbiome (the PROMISE Study): Protocol and Recruitment Strategy for a Cross-Sectional Study on Pathways That Affect the Gut Microbiome and Its Impact on Obesity

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 overconsumption 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 PRedictors linking Obesity and the gut MIcrobiomE (PROMISE) study, which characterizes the gut microbiome in 2 populations with 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 (2) the interactions between dietary intake; eating behavior; sweet, fat, and bitter taste perception; and 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 and 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 (body mass index [BMI] 18.5-24.9 kg/m²) or were obese (BMI ≥30.0 kg/m²). In addition to anthropometric measurements and assessment of the body fat content using dual-energy x-ray absorptiometry, participants completed sweet, fat, and bitter taste perception tests; food records; and sleep diaries; and they wore accelerometers to assess physical activity and sleep. Fasting blood samples were analyzed for metabolic and endocrine biomarkers and DNA extracted from fecal samples was analyzed by shotgun sequencing. Participants completed questionnaires on dietary intake, eating behavior, sleep, and physical activity. Data were analyzed 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 and networking within the Pacific communities. NZ European women were primarily recruited through Web-based 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 advance our understanding of the etiology of obesity and guide future intervention studies involving specific dietary approaches and microbiota-based therapies.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12618000432213; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370874

International Registered Report Identifier (IRRID)

RR1-10.2196/14529

Fat Sensation: Fatty Acid Taste and Olfaction Sensitivity and the Link with Disinhibited Eating Behaviour

Perception of fat taste, aroma, and texture are proposed to influence food preferences, thus shaping dietary intake and eating behaviour and consequently long-term health. In this study, we investigated associations between fatty acid taste, olfaction, mouthfeel of fat, dietary intake, eating behaviour, and body mass index (BMI). Fifty women attended three sessions to assess oleic acid taste and olfaction thresholds, the olfactory threshold for n-butanol and subjective mouthfeel ratings of custard samples. Dietary intake and eating behaviour were evaluated using a Food Frequency and Three-Factor Eating Questionnaire, respectively. Binomial regression analysis was used to model fat taste and olfaction data. Taste and olfactory detection for oleic acid were positively correlated (r = 0.325; p < 0.02). Oleic acid taste hypersensitive women had significantly increased n-butanol olfactory sensitivity (p < 0.03). The eating behaviour disinhibition and BMI were higher in women who were hyposensitive to oleic acid taste (p < 0.05). Dietary intake of nuts, nut spreads, and seeds were significantly correlated with high olfactory sensitivity to oleic acid (p < 0.01). These findings demonstrate a clear link between fatty acid taste sensitivity and olfaction and suggest that fat taste perception is associated with specific characteristics of eating behaviour and body composition.

Small particle size lipid emulsions, satiety and energy intake in lean men

Lipid emulsions have been proposed to suppress hunger and food intake. Whilst there is no consensus on optimal structural properties or mechanism of action, small particle size (small-PS) stable emulsions may have greatest efficacy. Fabuless®, a commercial lipid emulsion reported in some studies to decrease energy intake (EI), is a small-PS, 'hard' fat emulsion comprising highly saturated palm oil base (PS, 82nm). To determine whether small-PS dairy lipid emulsions can enhance satiety, firstly, we investigated 2 'soft' fat dairy emulsions generated using dairy and soy emulsifying agents (PS, 114nm and 121nm) and a non-emulsified dairy control. Secondly, we investigated a small-PS palmolein based 'hard' fat emulsion (fractionated palm oil, PS, 104nm) and non-emulsified control. This was a 6 arm, randomized, cross-over study in 18 lean men, with test lipids delivered in a breakfast meal: (i) Fabuless® emulsion (F_EM); (ii) dairy emulsion with dairy emulsifier (DE_DE); (iii) dairy emulsion with soy lecithin emulsifier (DE_SE); (iv) dairy control (DC_ON); (v) palmolein emulsion with dairy emulsifier (PE_DE); (vi) palmolein control (PC_ON). Participants rated postprandial appetite sensations using visual analogue scales (VAS), and ad libitum energy intake (EI) was measured at a lunch meal 3.5h later. Dairy lipid emulsions did not significantly alter satiety ratings or change EI relative to dairy control (DE_DE, 4035kJ; DE_SE, 3904kJ; DC_ON, 3985kJ; P>0.05) nor did palm oil based emulsion relative to non-emulsified control (PE_DE, 3902 kJ; PC_ON, 3973kJ; P>0.05). There was no evidence that small-PS dairy lipid emulsions or commercial Fabuless altered short-term appetite or food intake in lean adults.

Encapsulated green kiwifruit extract: a randomised controlled trial investigating alleviation of constipation in otherwise healthy adults

OBJECTIVES

Previous clinical trials have shown bowel function is improved through consumption of whole kiwifruit (Actinidia deliciosa). This study investigated whether encapsulated kiwifruit extract (1 g/day) could alleviate constipation in otherwise healthy adults.

METHODS

Forty adults with confirmed constipation entered this trial, of which 32 completed with >80% compliance. Two capsules were self-administered morning and evening for 2 periods, each of 3 weeks duration, separated by a 3+ week washout in a double blind, randomised, placebo controlled crossover. Inclusion criteria included constipation with <=3 bowel movements (BM) per week. Daily records of defecation frequency and stool characteristics were obtained throughout treatment, as well as a measurement of gastrointestinal symptoms rating scale (GSRS) and quality of life (QoL) before and after each intervention arm.

RESULTS

There was no difference in total BM over 3 weeks (p>0.05) or mean BM during each of weeks 1, 2 and 3 (p>0.05) between the kiwifruit extract and placebo when assessed from a faecal diary. There was also no detectable difference in defecation related scores of BM ease of defecation, volume, consistency or BM type assessed using Bristol stool chart scores. Nor was there a significant change in GSRS or QoL between pre and post treatment measures, when compared to placebo (p>0.05).

CONCLUSIONS

This trial showed that improvement in bowel function or comfort was not achieved through supplementation with 1 g/day freeze dried kiwifruit extract. Efficacy from prior kiwifruit powder and whole fruit trials indicate that investigating higher doses of encapsulated kiwifruit extract may be worthwhile.

Postprandial effects of a polyphenolic grape extract (PGE) supplement on appetite and food intake: a randomised dose-comparison trial

Background

There is recent evidence that glucose delivered to the distal small intestine (SI) may stimulate the ileal brake and inhibit appetite. High polyphenolic grape extract (PGE) has been shown to inhibit α-amylase and α-glucosidase activity, two key enzymes required for starch digestion, in vitro. It is hypothesised to slow digestion and absorption of starch in the proximal SI such that glucose may be delivered distally into the ileum and suppress appetite. This study investigated the safety and efficacy of a PGE supplement, delivered within a capsule and consumed with a high-starch breakfast, on appetite ratings and ad libitum energy intake (EI) at a subsequent lunch meal.

Methods

Twenty healthy, non-obese (BMI 18–28 kg/m²) male volunteers participated in a randomised, double blind, placebo controlled, three arm, cross-over study. Participants were administered (i) low dose PGE₅₀₀ (500 mg), (ii) high dose PGE₁₅₀₀ (1500 mg), and (iii) matched placebo with a 2MJ high-starch breakfast (white bread); followed 3 h later by a single item buffet-style lunch meal (pasta and meat sauce). Outcome variables were feelings of hunger, fullness, prospective thoughts of food (TOF) and satisfaction assessed using visual analogue scales (VAS); and ad lib energy and macronutrient intake at the lunch meal.

Results

There was no detectable effect of PGE₅₀₀ or PGE₁₅₀₀ compared with placebo (all, time*supplement interaction, P > 0.05) on VAS-assessed hunger, fullness, TOF or satisfaction. There was also no evidence that PGE significantly altered ad lib energy or macronutrient intake at the lunch meal relative to placebo (P > 0.05). EI following PGE₅₀₀ was +164 kJ higher than placebo (+5.3 %, P > 0.05); and EI following PGE₁₅₀₀was −51 kJ lower than placebo (−1.7 %, P > 0.05).

Conclusions

Whilst well tolerated, there was no evidence that encapsulated low dose PGE₅₀₀ or high dose PGE₁₅₀₀ consumed with a high starch breakfast meal altered postprandial hunger, fullness, TOF or satisfaction relative to a matched placebo. Nor was there evidence that either dose altered ad lib energy or macronutrient intake at an outcome meal.

Trial registration

ACTRN12614000041651