Non-pharmacological interventions designed to reduce health risks due to unhealthy eating behaviour and linked risky or excessive drinking in adults aged 18–25 years: a systematic review protocol

Excess body weight and heavy alcohol consumption are two of the greatest contributors to global disease burden [1, 2]. Being overweight and/or obese accounts for 5% of deaths worldwide [2] and is responsible for raising the risk of chronic diseases such as diabetes, heart diseases and cancers. Heavy alcohol consumption contributes to over 200 disease and injury conditions and is responsible for almost 6% of world deaths [1]. Risky or heavy alcohol use is the leading risk to health and wellbeing in young people, accounting for 7% of disability adjusted life years in 10–24-year-olds globally [3]. Rates of liver disease are linked to both alcohol use and obesity and they are rising rapidly in the UK [4, 5], particularly in those aged below 44 years [4]. Over the past 30 years, the UK has seen a fourfold increase in liver disease mortality and it is now the third most common cause of premature death, with 62,000 years of working life lost each year [6]. Most of these deaths are alcohol-related [7]. However, Non-alcohol fatty liver disease (NAFLD) is becoming increasingly common and it is now the most prevalent liver disorder in children and young adults with overall prevalence of between 2.6 and 9.8% in overweight individuals which rises to between 42 and 77% in those who are obese [6]. In addition, it has been shown that the combination of a raised body mass index (BMI) and heavy alcohol consumption can result in an intensified interaction creating a steeply elevated risk of liver disease in men and women [8] and that heavy drinking is associated with greater waist-hip-ratio in mid-life even when taking other lifetime influences into account [9].

Research on reducing excess body weight or heavy alcohol consumption typically occurs in isolation or as part of non-specific multiple behaviour change interventions. Recent exceptions have been behavioural modification work with middle-aged obese men who were also alcohol drinkers [10, 11] and the BeWEL study which sought to reduce weight by addressing diet, physical activity and alcohol amongst overweight or obese middle-aged adults at increased risk of colorectal cancer and other obesity-related comorbidities [12]. In the latter study, attention paid to alcohol was less than that paid to diet and physical activity. Strategies to jointly reduce alcohol consumption and address levels of overweight or obesity may produce greater health gains and be a more efficient use of resources than initiatives directed towards each pattern alone. As such, understanding this relationship is a global public health priority [8], particularly amongst younger people [13]. Adverse health behaviours begin to cluster during adolescence [14], and excess body weight and risky drinking have both been demonstrated to track into and throughout adulthood [15‐17]. Consequently, there is a strong rationale to intervene with young adults early; before these behaviour patterns become fully entrenched habits which lead to poorer health and social outcomes later in life. Further, there is increasing interest in developing and evaluating integrative interventions targeting multiple risk behaviours [18‐20].

Many eating rituals have become strongly linked to the use of alcohol and vice versa; for instance, salty snacks are often sold in public drinking venues and there is a popular concept of drinking alcohol with dinner or visiting fast food outlets after an evening out at drinking establishments [21]. Indeed, it has been suggested that unhealthy food choices are more likely to be made during and directly after a period of prolonged alcohol consumption [21] which could be due, at least in part, to the disinhibiting effect of alcohol which is a psychoactive substance that can alter usual behaviour. However, there are key differences when thinking about eating and unhealthy drinking behaviour. All individuals need to eat to survive, whilst many individuals choose to drink alcohol because it is perceived to be a pleasurable component of social life. Alcohol contains energy, but it is a nutritionally poor food source and does not stimulate satiety [22]. This may make it more likely for alcohol calories to be consumed in addition to energy intake from food.

Epidemiological data suggest that energy intake from alcohol, type of beverage and drinking pattern (i.e. high volume, high frequency) is associated with excess body weight and weight gain amongst adults [22, 23]. Few studies have explored this relationship amongst young adults. Those that do have shown a positive association between being overweight and/or obese and alcohol consumption, particularly amongst females [24, 25], whilst others have highlighted a conflict for some individuals between a wish to stay slim and also to drink alcohol as part of developing a social identity [26, 27]. Furthermore, there have been some reports of individuals choosing not to eat prior to socialising, so that they can drink alcohol and avoid weight gain; a phenomenon that has been termed ‘Drunkorexia’ [26]. This increases the likelihood of intoxication, where blood alcohol levels rise sharply and affect the brain and subsequent behaviour, which steeply increases the risk of acute harm from drinking.

Recent qualitative research demonstrates that young adults make trade-offs between food and alcohol consumption and levels of physical activity undertaken [28]. Little more is known about young adult’s perspectives on the relationship between alcohol consumption and unhealthy eating behaviour, i.e. patterns of food choice or behaviours that lead to adverse health outcomes, such as snacking, eating energy rich or high-sugar foods or avoiding eating so that alcohol calories do not lead to weight gain. It is increasingly recognised that health promoting interventions must acknowledge social and emotional needs [29, 30] as well as focus on reducing health risks. Recent work has begun to investigate wider cultural drivers of drinking and eating behaviour in early adolescence [31, 32], but this needs to extend to early adulthood in order to understand lifestyle choices in terms of co-occurring behaviours and wider socio-cultural drivers, and informs subsequent interventions.

Whilst a current Cochrane systematic review examines individual-, family- and school-led interventions for preventing multiple risk behaviours in individuals aged 8 to 25 years [19], no systematic review has examined the specific impact of interventions to reduce unhealthy eating and risky drinking and their health consequences amongst adults or individuals aged 18–25 years only. The systematic review proposed here will address this evidence gap by reviewing primary studies that have considered the effectiveness of preventative interventions focused on reducing unhealthy eating behaviour and linked risky alcohol use in young adults aged 18–25. We will focus on targeted interventions to improve health behaviour at an early stage of risk or harm, when it is likely to be most amenable to change. Such measures tend to include screening to identify relevant individuals, followed by the delivery of individual feedback, advice and/or counselling [33, 34].