Men's hidden fears about body fat are fuelling gym attendance motivated by feelings of guilt and shame rather than a desire to build muscle, new research has shown.

Psychology researchers from the UK and Australia discovered that while male attitudes towards muscle or body mass index (BMI) did not predict how frequently they would attend the gym, their perceptions of body fat did.

The researchers found that men worried about body fat were more likely than others to undertake spontaneous, unplanned work-outs - and warned that these 'sporadic' exercise patterns tend to be difficult to sustain over time.

The findings raise questions over the effect portrayals of the 'ideal body' online and in the media have on healthy exercise behaviours in an era of 'selfies'. This has important real-life implications for health and exercise professionals and their intervention programmes, the researchers suggest.

The study is the first of its kind to examine men's body attitudes alongside both their conscious (explicit) and non-conscious (implicit) motivations for attending the gym. The findings could help health and fitness professionals improve gym attendance in the long-term by focusing on pro-active goal-setting and personal autonomy, rather than body image.

The study was carried out by Dr David Keatley from the School of Psychology at the University of Lincoln, UK, and Kim Caudwell from Curtin University, Australia.

Dr Keatley, a specialist in the study of complex patterns of behaviour and motivation, said: "Coaches, trainers, and even 'gym buddies' need to be aware of individuals' motivations and reasons for attending a gym. Spontaneous gym goers are more likely to be motivated by guilt, shame or pressure, so it's important to turn this around and place a focus on positive feelings of achievement and pride, fostering a long-term healthier behaviour change.

"Anyone can be affected by what they see online, the social cues images can give, and the popular conceptions of an 'ideal body image'. With the recent growth of 'selfies' and the return of muscle-bound Hollywood hero icons like Vin Diesel and Hugh Jackman, there's a real risk that males may be more influenced to attend the gym more regularly and workout to a point where it becomes dangerous or detracts from their wellbeing.

"This study is important in showing that whilst they may be more unlikely to admit it, body dissatisfaction and dysmorphia can and do affect males as well as females, and therefore should be investigated fully."

To assess their motivations for exercising, 100 men completed a self-report questionnaire and a second test which evaluated their non-conscious motivation by measuring how long it took them to associate particular words with themselves.

All participants had a slightly elevated BMI and said they work out for around an hour, two or three times a week. Nearly 60 per cent of the men listed health and fitness as their primary reason for attending a gym or fitness activity. Just 16 per cent labelled appearance or amateur body building as their motivation, and eight per cent said training or competing was their main focus.

Participants responded to a series of statements about body image, for example "seeing my reflection makes me feel bad about my body fat and muscularity". They also evaluated a series of statements about their motivation, such as "I feel under pressure to exercise or work out regularly from people I know well". These were scored on a scale from one to four, with one being not very true and four being very true.

To examine hidden, non-conscious motivations, the researchers also asked participants to complete an Implicit Association Test (IAT), a task designed to assess automatic associations. It paired positive and negative feelings about exercising, such as 'spontaneous' and 'willing' or 'restricted' and 'forced', with words relating to the self and others, such as 'me' and 'mine' or 'they' and 'theirs'.

The study is published in the Journal of Strength and Conditioning Research.