Solving The Obesity Crisis by Correcting Weight Misperception and Information Nudges

Obesity is one of the most pressing health challenges of our time, yet public campaigns on diet and exercise have struggled to reverse rising global rates.

Assistant Professor Xuan Zhang from the School of Economics at Singapore Management University explores how a simple, low-cost intervention – a series of short, personalised text messages – can help people better understand their weight classification and adopt healthier habits.

Her team’s randomised controlled trial found that regular digital reminders significantly improved weight perception and diet among older adults, showing how behavioural insights can drive meaningful change in public health.

Read the original research: https://doi.org/10.1016/j.jebo.2024.04.029 

Transcript

Hello and welcome to ResearchPod. Thank you for listening and joining us today. 

Today, we explore new research from Assistant Professor Xuan Zhang of the School of Economics at Singapore Management University, whose work looks at one of the biggest public-health challenges of our time: if everyone knows the basics of diet and exercise, why are global obesity rates still rising, and what can be done to reduce them?

Professor Zhang’s study offers an elegantly simple yet highly effective answer. It suggests that one of the most effective ways to change behaviour may not be a new drug or a restrictive diet plan, but a series of short text messages that help people understand their weight classification more clearly and describe some simple ways they can improve their diet and exercise.

Obesity has become one of the defining health challenges of the twenty-first century. More people now die from illnesses linked to being overweight than from hunger. Worldwide, the World Health Organization estimates that obesity contributes to over 4 million deaths every year, making it the second leading cause of preventable death after smoking.

While many public-health campaigns have successfully reduced smoking through clear, repeated messaging, graphic warnings, and fiscal policies, obesity has proved much harder to tackle. Despite decades of nutrition labelling, exercise education, and government campaigns and policies, average body weight continues to climb.

Economists and behavioural scientists have begun to ask a different question: perhaps the problem isn’t just what people eat and how much exercise they get in, but what they think about their own body classification. In other words, do they even realize they are overweight or obese? 

Many individuals, especially in middle-aged and older populations, underestimate their weight category. If someone believes they are “about average” weight when, by medical definition, they are overweight or obese, then the motivation to change simply isn’t there. This gap between perceived and actual weight is known as weight misperception, and correcting it could be one of the missing links in obesity prevention. 

Previous research has found that behavioural barriers are the biggest factor stopping people from maintaining a healthy weight. The two primary barriers to controlling weight are misperception and inertia - in other words, not realizing they are overweight, and not knowing enough or procrastinating on doing something about it. 

To investigate this, Professor Xuan Zhang collaborated with Lanjie Wang, Seonghoon Kim, and Kanghyock Koh, forming a multidisciplinary team that combined economics, behavioural science, and public-health expertise. 

Together, they designed a randomized controlled trial—the gold standard for establishing causal effects. The trial was conducted between January and March 2022 and drew on data from over 2,500 participants of the Singapore Life Panel (SLP), a nationally representative longitudinal survey of adults aged 50 and older.

The researchers divided the participants into two groups. The treatment group received bi-weekly text messages via SMS or email over a period of twelve weeks, and the control group received no messages during that period.

The text messages had two goals: first, to remind participants of their current weight classification based on their body mass index, or BMI for short, and second, to provide concise, actionable information about diet or physical activity.

For example, one message read:

Maintaining a healthy weight is essential for your wellbeing. Being overweight increases the risk of heart disease, stroke, high blood pressure and diabetes. A healthy BMI ranges from 18.5 to 22.9.

Another focused on practical movement:

Stand or walk for five to ten minutes after sitting for more than ninety minutes. Choose foods and drinks with less sugar whenever possible.

Each participant in the treatment group received the full set of four message types—two focusing on weight awareness and two on healthy behaviour, six times in total, creating 24 touchpoints over the course of the three-month study period.

At the start and end of the trial, participants self-reported their height, weight, and perceived weight status. From these data, the team calculated each person’s BMI and determined whether they correctly perceived their weight category. The researchers also surveyed dietary habits, frequency of exercise, and self-reported wellbeing.

This study design allowed Zhang and her colleagues to isolate the direct impact of regular informational nudges from other lifestyle factors.

The first interesting finding of the research was that a majority of participants misjudged their own weight category. Among those medically classified as overweight or obese, many believed they were “normal” or only “slightly above average.” 

However, once participants received messages explicitly stating their BMI and corresponding health category, their self-perceptions shifted noticeably. People began to recognize that they were indeed overweight or obese, and that awareness changed how they responded to the health information provided.

The second major finding was that repetition matters. Earlier research had shown that one-time educational campaigns, whether in schools, clinics, or through emails or SMS, rarely lead to sustained behaviour change. This experiment demonstrated that repeated, low-cost digital reminders can gradually reshape both understanding and action, leading to positive health outcomes.

Over the twelve-week period, participants in the treatment group reported significant improvements in the quality of their diet, particularly reductions in sugary drink consumption and snacking. These effects persisted in follow-up surveys six months later, even after the text messages had stopped.

Interestingly, there was no statistically significant change in exercise habits or actual weight loss during that timeframe. The researchers suggest several possible reasons for this. First, the participants were mostly older adults, for whom physical limitations and time constraints can make new exercise routines difficult to maintain. Second, Singapore’s food culture, where healthy options such as soups, vegetables, and fresh seafood are widely available and low-cost, may have made dietary adjustments easier to adopt than activity-based ones.

Nonetheless, the study’s results point to an important behavioural conclusion: people act on information when it feels personalized, relevant, and is regularly reinforced.

The implications of this research extend well beyond Singapore. If periodic, personalized text reminders can influence diet and self-perception among older adults, similar strategies could be deployed across different populations, in different geographies, and potentially for different health issues.

Public-health authorities could integrate such reminders into national wellness programmes or healthcare systems. For example, regular digital messages could encourage medication adherence, dietary guidelines for heart disease and other conditions, or attending regular preventive screenings, all at a significantly lower cost compared to traditional campaigns.

From a policy perspective, Professor Zhang’s work contributes to the growing field of behavioural economics in health, which explores how subtle informational cues can nudge people toward better decisions. Rather than relying solely on taxation or regulation, policymakers can harness behavioural insights to make healthy choices easier and more automatic.

Economically, the potential benefits are enormous. In the United States alone, the annual medical cost of obesity exceeded $170 billion in 2019. Even a small reduction in obesity-related illnesses could translate into billions in savings and improved quality of life.

The study also highlights the importance of self-perception as an entry point for change. When people see an accurate reflection of their health status, delivered respectfully and consistently, they are more likely to take action. 

Every experiment has its limitations, and Zhang and her colleagues are careful to acknowledge them. The sample consisted primarily of well-educated, urban Singaporeans aged 50 and above. These individuals may already possess higher baseline health literacy than the general population.

Future studies could extend this research to younger or less-educated groups, or to populations in other countries where cultural attitudes toward weight are different. Longer-term follow-up would also help determine whether improved dietary habits eventually lead to measurable weight reduction and better health outcomes.

Professor Zhang hopes that by collaborating with public-health agencies, future projects can combine digital nudges with community-based support, offering both information and encouragement in real time. 

In the words of the author Xuan Zhang, “Our research shows that informing overweight and obese people about their correct weight status, and by providing low-cost, high-frequency educational information, it can have huge implications for reducing misperception and for treating obesity. Participants showed substantial improvements in dietary actions, although no changes in exercise, implying that low-cost dietary education can be potentially effective in saving long-term medical costs due to obesity.”  

That’s all for this episode. Thanks for listening. Links to the original research can be found in the shownotes for this episode. And don’t forget to stay subscribed to ResearchPod for more of the latest science!

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