Satiety, Microbiome, Appetite Regulation, and Tracking Energy Across Targeted Snacks: Chronic Study

Diet, and snacking behaviour in particular, plays an important role in long-term health. Snacking now contributes substantially to daily energy intake in the UK and US: data from the ZOE PREDICT study show that 95% of adults snack at least once a day, with snacks accounting for around a quarter of daily energy intake (2.28 snacks/day). However, the average UK snack has a poor nutrient profile, high in refined carbohydrates, added sugars, and saturated fat, and low in fibre and micronutrients, a pattern linked to poorer cardiometabolic health. Despite public health guidance to consume at least 30g of fibre a day, UK adults consume an average of around 20g/day. However, the composition and timing of a snack are important determinants of its effects on hunger, energy, and other health markers.

This trial evaluates an intervention (2 x snack bars) against a control (2 x snack bars that reflect the average nutrient profile of snacks currently sold in the UK). Using a control snack bar means any effects observed can be attributed to the specific formulation of the intervention snack bar, rather than simply to a change in snacking habits or a reduction in overall snack consumption.

The primary aim of the study is to determine whether the intervention snack bars reduce subjective daily hunger over 4 weeks of daily use, compared with control snack bars representative of the average UK snack nutrient profile. The study will be conducted in 2 phases. In this phase (phase 2; chronic randomised controlled trial), 100 participants (50 per arm) will eat the intervention or control bars daily for 4 weeks. Secondary aims for this phase include the bar's effects on gut microbiome composition, gastrointestinal symptoms, bowel habits (frequency and consistency), subjective mood and energy, sleep quality, and anthropometric measures. The design allows the chronic effects of the intervention snack bars to be assessed when the bars are eaten regularly in place of habitual snack foods.

Inclusion criteria

• Willing and able to follow the study protocol
• Willing and able to provide informed consent
• Regular consumption of snacks (≥2 per day)
• Fibre intake <20 g/d
• Living in the UK

Exclusion criteria

• Have BMI of less than 18.5 kg/m² or more than 40 kg/m²
• Have an allergy or intolerance to ingredients in the intervention or control snack bars (including inulin) or cannot eat the food products safely and comfortably for any reason
• Have a personal medical history of inflammatory bowel disease, coeliac disease, Crohn's disease, irritable bowel syndrome, chronic constipation, or chronic diarrhoea
• Have started a new supplement in the past month, or are unwilling to maintain current supplement use throughout the study
• Previously purchased any ZOE products (including Daily30, ZOE gut health bar or ZOE app membership).
• Have taken any medication or product that may modify the measured study outcomes, in the past 3 months (including but not limited to: fibre supplements, antibiotics, non-topical steroids or other immunosuppressive medicines, probiotics or prebiotics, metformin, GLP-1 receptor agonists, lipid-lowering medications such as fibrates, statins, PCSK9 inhibitors, non-steroidal anti-inflammatory drugs)
• Have used opiate pain medication or a proton pump inhibitor for 8 or more consecutive days during the past 3 months
• Have experienced a heart attack, stroke or major surgery in the last 2 months
• Have received treatment for cancer in the last 3 months
• Are currently pregnant, breastfeeding or planning a pregnancy
• Are diagnosed with an eating disorder, type 1 diabetes mellitus or type 2 diabetes mellitus