Overweight and related metabolic disorders are now one of the global public health challenges. Visceral fat is particularly dangerous – the fat that accumulates around internal organs and increases the risk of type 2 diabetes, as well as cardiovascular disease.
Until now, the assessment of overweight has mostly used anthropometric indicators, such as body mass index (BMI); however, in assessing overweight, it should be taken into account that it can be metabolically different − in some individuals, overweight is relatively favourable if the amount of visceral fat is within the normal range, while in other cases it is metabolically unfavourable if the amount of visceral fat is increased. Since BMI is unable to differentiate fat distribution and the amount of visceral fat, in such cases more essential information is provided by methods such as bioimpedance analysis, as well as imaging diagnostic methods that allow the volume of visceral adipose tissue to be directly assessed.
Gita Erta’s doctoral thesis The Association of Functional Activity of Salivary Amylase with Overweight and Carbohydrate Metabolism Disorders shows that a small enzyme in saliva may prove to be an important signal of how our body responds to carbohydrates and how “bad” fat is formed.
How was the link between saliva and metabolism tested?
“We are all very individual – different not only in terms of appearance, but also in terms of how our body responds to food,” emphasises Gita Erta. These very differences were what interested her in conducting the study.
The study involved 67 women, of whom 60 were overweight, while seven women with normal weight formed the control group. The researcher analysed salivary alpha-amylase activity and its association with:
- body mass index and the amount of visceral fat,
- carbohydrate metabolism indicators (glucose, active GLP-1, glucagon, insulin resistance indices),
- lipid profile,
- cytokines.
Women with overweight followed two different diets for 12 weeks — an energy-deficit diet or a low-starch diet — in order to assess how dietary changes affect metabolism depending on salivary enzyme activity. In turn, no dietary control was carried out for the women with normal weight included in the control group.
What did the study reveal about the salivary enzyme and metabolic risk?
Salivary alpha-amylase activity is an independent and statistically significant predictor of visceral fat. Put simply, how actively this enzyme works is one of the factors that influences how much visceral fat accumulates in the body, which in turn contributes to insulin resistance.
As the author of the study explains, people perceive and process carbohydrates differently, or have different sensory perception of food, which affects the neuroendocrine response and the way insulin is secreted. If insulin is secreted excessively over a long period of time, it may promote the formation of visceral fat and metabolic disorders. Thus, salivary alpha-amylase may become an early signal that allows an increased risk to be detected in time, before clinical problems appear.
The study also found an association between salivary alpha-amylase activity and butyrate – a short-chain fatty acid that has a beneficial effect on gut health and metabolism.
The results obtained open up opportunities in the future to develop personalised nutrition recommendations based not only on general advice, but also on a specific person’s metabolic profile. In the future, the researcher also hopes to include saliva analysis in an integrated metabolic risk assessment panel, combining it with other hormones and cytokines. In the long term, this could even mean smart sensors and artificial intelligence solutions that help doctors make more precise, personalised decisions.
The summary of Gita Erta’s doctoral thesis is available in the RSU e-resource repository
