Published on 30 September 2021

    Taking advantage of your sense of smell to help you lose weight – could this really work?

    Some weight-loss devices say they can. By diverting smells away from the nose – for instance, through straw-like nasal inserts – these products purportedly work by blocking the smell of food and consequently, curbing the user’s appetite. 

    But just how effective are these devices? “Currently, there are no commercially approved interventions for human use,” said Asst Prof Asim Shabbir, Director, Centre for Obesity Management and Surgery, National University Hospital (NUH).

    While smells are inextricably linked to appetite, contributing to between 40% and 80% of our sense of taste, the connection is not so straightforward. 

    For instance, a study found that the smell of dark chocolate – despite having a pleasant odour – led to a decrease in appetite and reduced cravings among young women. 

    In contrast, the smell of vanilla caused the opposite effect, said Asst Prof Asim, who is also Senior Consultant at NUH’s Division of General Surgery.

    “Unpleasant odour elicits a measurable consistent aversive response,” he explained.  “Pleasant odour, on the other hand, may induce differential responses.”

    This could be due to the complexity of the phenomenon. Appetite is controlled by many overlapping signals and systems: sensory, cognitive, hormonal, and metabolic. And while hunger signals are promoted by olfactory cues, satiety (or fullness) is driven by feedback from the gastrointestinal system. 

    Furthermore, sensitivity to specific odours varies among individuals, added Asst Prof Asim. Here, too, different factors affect appetite: from the quality of the aroma and the texture of the food, to even bite-size and eating speed.

    As such, tailoring these features – such as by consuming food without odour, or with unpleasant odours – may indeed influence a person’s feeling of satiety and encourage them to eat less, potentially helping weight loss. 

    “Although this may not be a practical option that consumers would like,” quipped Asst Prof Asim. 

    In consultation with Asst Prof Asim Shabbir, Director, Centre for Obesity Management and Surgery, NUH & Senior Consultant, Division of General Surgery (Upper Gastrointestinal Surgery), Department of Surgery, NUH.