Being overweight increases your risk of heart disease and stroke, type 2 diabetes, muscle and joint problems, and some cancers (including endometrial, breast and colon). And currently almost two in three Australian adults are overweight or obese.

The increased risk for health problems starts when you are only very slightly overweight and increases as the excess weight increases. The risks associated with a poor diet and high BMI are the top two disease burdens in Australia, ahead of smoking. So reducing overweight and obesity is a government health priority.

Read more: How obesity causes cancer, and may make screening and treatment harder

But campaigns intending to inform individuals of the risks of excess weight, and consequently motivate them to lose weight, have been accused of promoting “fat shaming”. For example, the “Grabbable Gut” campaign came under fire, accused of intending to disgust and shock the viewer, thereby promoting fat shaming.

Fat stigma can adversely affect the physical and mental health of overweight people, and demotivate healthy behaviours, the very behaviours health campaigns hope to improve.

Is all talk of overweight for health fat shaming?

The effects of fat shaming are real and stigmatisation should be avoided. No one should be made to feel so bad about themselves that their health is at risk. But the increased disease risk due to excess weight is also very real. So how do we address this global health problem without making overweight people feel guilty?

For both individual and population health, we need to be able to discuss the risks of excess weight, as well as the health consequences of fat shaming. Compassion and understanding are needed in addressing both problems. This includes acknowledging that health is not just about weight status, yet weight status can and does affect health.

But the main thing that should be highlighted alongside these discussions is that there are many factors that influence human behaviour. Whether we exercise regularly or eat healthy foods is influenced by our age, gender, motivation, sense of capability, and mental health. We’re also influenced by broader factors such as the availability, cost and convenience of physical activity opportunities, and healthy and unhealthy food options and marketing strategies.

The influence of social norms

The social environment is a key influence on human behaviour. The attitudes, behaviours and traits of those around us inform what is considered “normal” and acceptable, influencing our own attitudes and behaviours. We are more likely to be active, eat well, and maintain a healthy weight if those around us are active, eat well, and maintain a healthy weight.

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This social influence is expressed as pressure to conform to the “norm”. Extreme deviations from what is considered “normal” often result in stigmatisation. This can be seen for almost any trait or behaviour.

With the majority of individuals now overweight or obese, our perceptions of “normal” body weight no longer reflect what is considered healthy, and being “a bit overweight” is accepted as normal. This allows the rates of overweight and obesity to continue to rise with little public concern. It also means people who are “a bit overweight” may not realise their current weight exceeds health recommendations.

As “normal” body weight increases, “thin” and “healthy weight” become deviations from the norm, and “thin shaming” also occurs.

So how can we influence healthy behaviours?

Overweight and obesity, along with poor diets and insufficient physical activity, are population-wide problems. Approaches targeting individuals are unlikely to be effective, especially when such approaches offend those they aim to motivate and may support stigmatisation. Population-wide strategies are needed.

Policies targeting populations rather than individuals can shape the environment to provide convenient and affordable healthy options for food and physical activity.

Improving public transport, cycling and walking infrastructure would make active transport options more appealing, improving physical activity levels (and reducing reliance on cars, fossil fuel consumption and alleviating traffic congestion to boot).

Food pricing, placement and promotions within supermarkets and other food vendors influence food selection, as can food marketing more broadly. We need policies in place to ensure nutritious foods are affordable and promoted above junk foods high in calories and low in nutrients.

Read more - Choosing healthy food: how your surroundings affect your dining choices

People who want to change their health behaviours, or are struggling with issues relating to stigmatisation, should talk to their doctor. And we should all be respectful of diversity, at whichever end of the spectrum.