A salivary enzyme may help predict an increased risk of harmful fat accumulation

Overweight and the metabolic disorders associated with it are now among the major global public health challenges. Particularly dangerous is visceral fat – the fat that accumulates around internal organs and increases the risk of type 2 diabetes and cardiovascular disease.

So far, assessments of excess weight have relied mainly on anthropometric indicators such as body mass index (BMI). However, when evaluating overweight, it is important to bear in mind that it can differ metabolically: for some individuals, excess weight is relatively benign if the amount of visceral fat remains within the normal range, whereas in other cases it is metabolically unfavourable if visceral fat is increased. 

Since BMI cannot distinguish fat distribution or quantify visceral fat, methods such as bioimpedance analysis and imaging techniques, which allow direct assessment of visceral adipose tissue volume, provide more meaningful information in such cases.

Gita Erta’s doctoral thesis, The association of salivary amylase functional activity with overweight and disorders of carbohydrate metabolism, 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 develops.

How was the link between saliva and metabolism tested?

'We are all highly individual – different not only in appearance, but also in how our bodies respond to food,' emphasises Erta. These differences were precisely what sparked her personal interest in carrying out the study. The study involved 67 women, 60 of whom were overweight, while seven women of 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,
• markers of carbohydrate metabolism (glucose, active GLP-1, glucagon, and indices of insulin resistance),
• lipid profile,
• cytokines.

For 12 weeks, women with overweight followed one of two different diets – an energy-deficit diet or a low-starch diet – in order to assess how dietary changes affect metabolism depending on salivary enzyme activity. By contrast, no dietary control was applied to the women of normal weight in the control group.

What did the study reveal about salivary enzymes and metabolic risk?

Salivary alpha-amylase activity is an independent and statistically significant predictor of visceral fat. Put simply, how active this enzyme is constitutes one of the factors influencing how much visceral fat accumulates in the body, which in turn contributes to insulin resistance.

As the author of the study explains, people differ in how they perceive and process carbohydrates; in other words, sensory perception of food varies from person to person, influencing the neuroendocrine response and the pattern of insulin secretion. If insulin is secreted excessively over a prolonged period, this can promote the formation of visceral fat and metabolic disorders. Salivary alpha-amylase may therefore become an early signal that makes it possible to detect increased risk before clinical problems appear. The study also identified an association between salivary alpha-amylase activity and butyrate – a short-chain fatty acid that has beneficial effects on gut health and metabolism.

The results obtained open up possibilities for developing personalised nutritional recommendations in the future, based not only on general advice but on an individual person’s metabolic profile. Looking ahead, the researcher also hopes to include saliva analysis in an integrated metabolic risk assessment panel, combining it with other hormones and cytokines. In the longer term, this could even lead to smart sensors and artificial intelligence solutions that help doctors make more precise, personalised decisions.

A summary of Erta’s doctoral thesis is available in the RSU e-resource repository.