New study finds link between smell and obesity

Assessing current knowledge of the interaction between obesity and olfaction.


Scientists at the University of Otago have made a groundbreaking revelation by identifying an association between smell and obesity. The study suggests that there is a strong link between a person’s body weight and their smell ability – the better a person can smell, the more likely the person is to be slim, or vice versa.

According to Dr Mei Peng, lead author of the study, Out of the five senses- smell to be the least understood, and yet says it is maybe the most imperative sense for affecting eating behavior through distinguishing and separating between various flavors.

Dr Peng said, “We found obese people’s ability to detect and discriminate smell was not as efficient as slim people. This can result in obese people having a higher chance of making poor food choices because they will need other forms of stimulation to enjoy the food. For example, they might choose, or be more attracted to, saltier and tastier foods such as bacon and maple syrup instead of blander foods such as low-fat cereal with less sugar.”

Through systematic review/meta-analysis, the research gathered all the related scientific papers that touched on body shape and smell ability, collecting information of 1432 individuals from empirical and clinical worldwide studies.

Of note is that body weight needs to pass a specific benchmark for the connection to become obvious – so the reduction in capacity to distinguish and separate between various smells was more prominent among individuals who were close to being obese. The scientists conjecture that once an individual is obese their metabolism adjusts a few peptides and hormones which affect the gut-brain signaling pathway.

This prompts another region of thought around two careful obesity medicines; stomach removal and gastric bypass. The research found stomach removal can really enhance smell capacity, though other obesity surgeries don’t have a similar impact on individuals’ smell ability.

Dr Peng said, “Cutting the stomach could change nerves in the stomach that affect the gut-brain pathway, so smell changes could be the key to the difference between the two surgeries – essentially the smaller size of the stomach might not be the factor that leads to weight loss, it is more likely due to the gut-brain pathway being reset.”

Dr Peng hopes the research will increase awareness around the link between human’s eating behavior and our senses. She is hoping to continue the line of research to investigate the reward-factor smell has in various body-shape groups.

The findings are published in the international Obesity Reviews journal.


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