RSPH wants the introduction of symbols for jogging, cycling and other exercise. According to its example, a chocolate bar would be labelled to be equivalent to 40 minutes of running, 49 minutes of cycling or 29 minutes of swimming.
RSPH's own research found two thirds (63%) of people would support introducing activity-equivalent labelling, with more than half (53%) saying it would cause them to make positive behaviour changes such as choosing healthier products, eating smaller portions or doing more physical exercise.
As well as moderating excessive calorie consumption, it is hoped that such calorie labelling would help promote and normalise physical activity, which has a wide range of physical and mental health benefits beyond weight management.
People surveyed by RSPH were three times more likely to indicate they would undertake physical activity after viewing the calorie labels than after viewing current 'traffic light' nutritional labels alone.
RSPH chief executive Shirley Cramer CBE said: "Although nutritional information provided on food and drink packaging has improved, it is evident that it isn't working as well as it could to support the public in making healthy choices. Activity-equivalent calorie labelling provides a simple means of making the calories contained within food and drink more relatable to people's everyday lives, while also gently reminding consumers of the need to maintain active lifestyles and a healthy weight.
"Given the responsibility of the food industry in tackling the obesity epidemic, we believe activity-equivalent calorie labelling could provide the nudge many people need to be more active and support their customers to make healthier choices."
UKactive executive director Steven Ward said: "Anything that can get people more physically active is a step in the right direction. Ukactive welcomes this paper as another sign that getting more people, more active, more often is at the top of public health professionals' minds."
Ward of the not-for-profit group added: "We see a lot of health messaging telling us off, to eat and drink less, which, although correct, doesn't work for everyone. Encouraging people to be more active is a positive message, more about supporting people to start rather than imploring them to stop. Physical activity has been described by the Academy of Medical Royal Colleges as a 'miracle cure' so we should treat it as just that."
Calorie labelling on alcohol has gathered momentum recently, as many brewers are set to join AB InBev UK in voluntarily providing nutritional information.