Modifying Alcohol Consumption to Reduce Obesity (MACRO): development and feasibility trial of a complex...

Obese men who consume alcohol are at a greatly increased risk of liver disease; those who drink > 14 units of alcohol per week have a 19-fold increased risk of dying from liver disease.

To develop an intervention to reduce alcohol consumption in obese men and to assess the feasibility of a randomised controlled trial (RCT) to investigate its effectiveness.

The intervention was developed using formative research, public involvement and behaviour change theory. It was organised in two phases, comprising a face-to-face session with trained laypeople (study co-ordinators) followed by a series of text messages. Participants explored how alcohol consumption contributed to weight gain, both through direct calorie consumption and through its effect on increasing food consumption, particularly of high-calorie foodstuffs. Men were encouraged to set goals to reduce their alcohol consumption and to make specific plans to do so. The comparator group received an active control in the form of a conventional alcohol brief intervention. Randomisation was carried out using the secure remote web-based system provided by the Tayside Clinical Trials Unit. Randomisation was stratified by the recruitment method and restricted using block sizes of randomly varying lengths. Members of the public were involved in the development of all study methods.

Men were recruited from the community, from primary care registers and by time-space sampling (TSS). The intervention was delivered in community settings such as the participant's home, community centres and libraries.

Men aged 35-64 years who had a body mass index (BMI) of > 30 kg/m² and who drank > 21 units of alcohol per week.

The screening methods successfully identified participants meeting the entry criteria. Trial recruitment was successful, with 69 men (36 from 419 approached in primary care, and 33 from 470 approached via TSS) recruited and randomised in 3 months. Of the 69 men randomised, 35 were allocated to the intervention group and 34 to the control group. The analysis was conducted on 31 participants from the intervention group and 30 from the control group. The participants covered a wide range of ages and socioeconomic statuses. The average alcohol consumption of the men recruited was 47.2 units per week, more than twice that of the entry criterion (> 21 units per week). Most (78%) engaged in binge drinking (> 8 units in a session) at least weekly. Almost all (95%) exceeded the threshold for a 19-fold increase in the risk of dying from liver disease (BMI of > 30 kg/m² and > 14 units of alcohol per week). Despite this, they believed that they were at low risk of harm from alcohol, possibly because they seldom suffered acute harms (e.g. hangovers) and made few visits to a general practitioner or hospital.

The intervention was delivered with high fidelity. A high follow-up rate was achieved (98%) and the outcomes for the full RCT were measured. A process evaluation showed that participants engaged with the main components of the intervention. The acceptability of the study methods was high.

This feasibility study developed a novel intervention and evaluated all of the stages of a RCT that would test the effectiveness of the intervention. The main stages of a trial were completed successfully: recruitment, randomisation, intervention delivery, follow-up and measurement of study outcomes. Most of the men recruited drank very heavily and were also obese. This places them at a very high risk of liver disease, making them a priority for intervention.

A RCT to test the effectiveness and cost-effectiveness of the intervention.

Current Controlled Trials ISRCTN55309164.

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 19. See the NIHR Journals Library website for further project information.