Obesity is not caused by a lack of will power and policymakers must do more to recognise the social and environmental causes if they are to crack the obesity problem, according to a panel of expert psychologists.

The British Psychological Society report, Psychological perspectives on obesity: Addressing policy, practice and research priorities, says obesity is a complex problem and increasing the stigma that comes with obesity by seeing it as a moral failing will only make things worse. Stigma experienced when using health services is particularly damaging as it makes people less likely to seek help in future.

Chartered psychologist Dr Angel Chater from the University of Bedfordshire, one of the authors of the report, said: “Adult obesity levels in England increased by 18 per cent between 2005 and 2017, and there were similar increases in Scotland, Northern Ireland and Wales. This cannot be explained by a sudden loss of motivation across the four nations of the UK.

“The increase in obesity can in part be attributed to changes in the food supply and physical activity environment."

Some people have a high genetic risk of developing obesity

The report states that the people most likely to be an unhealthy weight are those who have a high genetic risk of developing obesity and lives shaped by work, school and social environments that promote overeating and inactivity. Psychologists are able to take account of all these factors and help develop treatments and policy initiatives that have the best chance of being successful.

The report calls for government to ensure every initiative aimed at promoting a healthy weight is informed by psychological evidence. It also says weight management services are best delivered by multidisciplinary teams that include psychologists.

All health professionals working in obesity services should be trained in the psychological understanding of obesity to increase their awareness of the factors that can contribute to the condition and to the success or failure of treatment.

Sarb Bajwa, chief executive of the British Psychological Socieety, said: “The government acknowledged that obesity was a threat to the health of the nation back in 1991, but the problem has continued to get worse. We need a similar effort on obesity to the one we have seen on smoking.

“It has taken action at all levels for decades, from government policy to helping individual smokers, but we are now seeing significant reductions in the level of smoking and the health problems it causes. Psychologists have the science and clinical experience to help the health service do the same for obesity.

“We can help, not just by devising ways of helping individuals, but also by advising on public policy which will help create an environment in which people find it easier not to become obese in the first place.”