New research to be presented at the European Congress on Obesity (ECO 2025), taking place in Malaga, Spain, from 11 to 14 May, highlights the link between dietary sodium intake and the risk of systemic and abdominal obesity. The study was led by Annika Santalahti and colleagues at the Finnish Institute of Health and Welfare in Helsinki, Finland.
General obesity is often assessed using body mass index (BMI), which is defined by the World Health Organization (WHO) as 30 kg/m² or higher. Abdominal obesity is the accumulation of excess fat around the abdomen and internal organs, leading to an increase in waist circumference. This type of obesity is particularly concerning because it is associated with an increased risk of cardiovascular disease.
There is growing evidence that sodium intake is positively associated with obesity risk. Finland's sodium intake has declined after peaking in the 1970s, when the country had some of the highest heart disease rates in the world. Sodium intake has remained relatively stable since 2007.
The authors explain: "Contrary to popular belief, high sodium intake is not primarily caused by unhealthy foods, but from daily diet. In Finland, most sodium comes from processed meat products, bread and dairy products, especially cheese. The problem of high sodium intake cannot be solved only at the individual level - it also requires changes at the population level, and this can only be achieved through cooperation with the food industry."
In the new study, the authors examined the association between sodium intake, urinary sodium concentration, and systemic and abdominal obesity in Finnish adults. They used population data (2,222 men, 2,792 women, ages 18 and over) from the National Financial Health 2017 Study. Sodium intake was estimated using a validated food frequency questionnaire. The researchers collected random urine samples from a subsample of participants (558 men and 702 women). Body mass index and waist circumference were used to measure total body adiposity and abdominal adiposity.
Sodium intake and urinary sodium concentration were stratified by sex into quartiles (25% of each group from highest to lowest) and statistical modeling analyzes were performed, adjusting for common sociodemographic and lifestyle confounders. In the validity analysis, random urine samples were compared with 24-hour urine samples.
The study results showed that except for the lowest quartile of women, which was still below the recommended limit, the median sodium intake (converted into salt intake) in all quartiles was higher than the recommended value (5 grams or less per day recommended by WHO). For men and women combined, sodium intake in the highest quartile was 2.3 times higher than in the lowest quartile.
The study found that the difference in sodium intake between men and women, which was consistently higher in men, was about the same across quartiles. Based on self-reported values from the questionnaire, average sodium intake in the top quartile was approximately 4900 mg/day for men and 3750 mg/day for women. These values translate into a daily salt (sodium chloride) intake of more than 12 grams for men and more than 9 grams for women - more than twice the WHO recommended intake for men and almost twice as much for women.
The authors found that participants with high dietary sodium intake or high urinary sodium concentrations were more likely to develop systemic obesity or celiac obesity. In fully adjusted models, women in the highest quartile (25th percentile) of sodium intake were 4.3 times more likely to have general obesity and 3.4 times more likely to have celiac obesity compared with women in the lowest quartile. Women in the second highest quartile of sodium intake were also 2.4 times more likely to have systemic obesity than women in the lowest quartile.
Similar associations were observed when urinary sodium concentration was used as the independent variable, indicating that food questionnaire-estimated sodium intake was consistent with urine test results. For example, using urinary sodium concentrations, women in the highest quartile were 4.8 times more likely to be obese than women in the lowest quartile (similar to a 4.3-fold increase in questionnaire-assessed sodium intake).
For men, although the pattern of obesity risk with increasing questionnaire-assessed sodium intake was similar to that for women, the results did not reach statistical significance in all quartiles. However, in terms of urinary sodium concentration, the results for men were statistically significant: In the fully adjusted model, men in the highest quartile (25th percentile) of urinary sodium concentration were 6 times more likely to have general obesity and 4.7 times more likely to have abdominal obesity than men in the lowest quartile.
Validity analyzes demonstrated reasonably good agreement between sodium found in spot urine and 24-hour urine collections, suggesting that subjects can be well classified into low- and high-sodium intake categories based on spot urine sodium concentration.
Regarding the stronger association shown by men, the authors said: "In general, men consumed more food and consumed more foods that are major sources of sodium, such as meat products, breads and baked goods, and cheese. Our analyzes were adjusted for total energy intake, so the stronger association shown by men may be due to higher salt intake relative to total energy intake. However, regardless of the magnitude of the association, the associations tended to be similar for men and women."
The authors concluded: "These results strengthen the evidence for an association between sodium intake and obesity, with similar results observed for dietary sodium and urinary sodium concentrations. A deeper understanding of the biological mechanisms underlying this relationship is critical."
Regarding the relationship between sodium intake and obesity, the authors stated: "The relationship between salt intake and obesity is unclear, and there are currently no conclusive explanations for gender differences and general phenomena. Research data are still very limited, but possible biological explanations include changes in satiety hormone secretion caused by long-term high salt intake. High salt intake may also be Indicators of overall nutritional quality - Excessive consumption of high-sodium foods is associated with an increased risk of obesity, which may reflect excessive consumption of ultra-processed high-sodium foods. However, further research is needed on the overall nutrition and nutritional quality of people on high-sodium diets, as well as the biological mechanisms of high sodium intake, such as the effects on satiety, gut microbiota, and body composition."
They added that to address excessive sodium intake, all aspects of the diet need to be carefully looked at. They said: "We believe that the food industry plays an important role in reducing population sodium intake, as most food consumption comes from sources other than unprocessed primary production. It is important to pay attention to the salt content of commonly eaten foods, as these foods account for a large proportion of daily sodium intake. Of course, general changes in the dietary environment also play a role, such as whether food is cooked at home, consumed in restaurants or as takeaway food."
Compiled from /ScitechDaily