High sodium intake strongly linked to increased risk of both general and abdominal obesity, Finnish study finds

A new Finnish study, to be presented at the upcoming European Congress on Obesity (ECO 2025) in Malaga, Spain (11–14 May), has found a significant association between dietary sodium intake and the likelihood of both general and abdominal obesity. The research, led by Annika Santalahti from the Finnish Institute for Health and Welfare in Helsinki, offers further evidence of the potential health risks posed by excessive sodium consumption.

General obesity is defined by a person’s body mass index (BMI), with the World Health Organization (WHO) stating that a BMI of 30 kg/m² or more constitutes obesity. Abdominal obesity, on the other hand, refers to the accumulation of fat around the abdomen and internal organs, leading to an enlarged waist circumference. This central distribution of fat is known to increase the risk of cardiovascular diseases.

Background: A Growing Body of Evidence

The study builds on a growing body of evidence suggesting a positive relationship between high sodium intake and increased risk of obesity. Historically, sodium consumption in Finland had declined from the 1970s—when the country faced some of the world’s highest rates of heart disease—but has largely plateaued since 2007.

The researchers explain:

“Contrary to popular belief, high sodium intake is not mainly caused by unhealthy foods, but by ordinary everyday food. In Finland, most sodium is obtained from processed meat products, bread and dairy products, especially cheese. High sodium intake cannot only be addressed at an individual level—changes at the population level are also needed and can only be achieved through cooperation with the food industry.”

Study Design and Methods

This new study examined data from the National FinHealth 2017 Study, a population-based study of Finnish adults aged 18 and over. It included 2,222 men and 2,792 women. Sodium intake was estimated using a validated food frequency questionnaire, and spot urine samples were collected from a subsample of participants (558 men and 702 women). General obesity was assessed using BMI, while waist circumference measurements were used to determine abdominal obesity.

Sodium intake and urine sodium concentrations were divided into sex-specific quartiles (four equally sized groups based on intake levels). Statistical modelling was conducted to examine associations, adjusting for sociodemographic and lifestyle-related confounders. Spot urine samples were validated by comparison with 24-hour urine collection data.

Key Findings: Sodium Intake Exceeds Recommendations

Across all but the lowest quartile of women, sodium intake exceeded WHO recommendations of 5 grams of salt (sodium chloride) per day. In the highest quartile, sodium intake was 2.3 times higher than in the lowest quartile for both men and women combined. Men consistently reported higher sodium intake than women across all quartiles.

Self-reported estimates from food questionnaires suggested that men in the highest quartile consumed approximately 4,900 mg of sodium per day, equivalent to over 12 grams of salt. Women in the same quartile consumed around 3,750 mg of sodium daily—translating to roughly 9 grams of salt. These levels significantly exceed WHO recommendations and suggest a worrying trend.

Obesity Risk Increases with Sodium Intake

The researchers found that participants with higher dietary sodium intake or higher urine sodium concentrations were more likely to be living with either general or abdominal obesity. Among women, those in the highest quartile for sodium intake were:

• 4.3 times more likely to be living with general obesity, and
• 3.4 times more likely to be living with abdominal obesity compared to those in the lowest quartile.
  

Women in the second highest quartile also had significantly increased risk, being 2.4 times more likely to have general obesity than those in the lowest quartile.

Comparable findings emerged when using urine sodium concentrations. For instance, women in the highest urine sodium quartile were 4.8 times more likely to be living with obesity than those in the lowest quartile—almost identical to the 4.3-fold increase observed through dietary data.

Stronger Associations Observed in Men (Urine Data)

While men showed a similar pattern in obesity risk when sodium intake was assessed through dietary questionnaires, the results were not statistically significant across all quartiles. However, when analysing urine sodium concentrations, statistically significant associations emerged. Men in the highest urine sodium quartile were:

• 6 times more likely to be living with general obesity, and
• 4.7 times more likely to be living with abdominal obesity compared to those in the lowest quartile.
  

The authors note that the spot urine measurements corresponded moderately well with 24-hour collections, suggesting a reasonably accurate categorisation of participants into high and low sodium intake groups.

Possible Explanations and Biological Mechanisms

On the stronger associations observed in men, the authors explain:

“In general, men consume more food, and also more of foods that are the main food sources of sodium in the diet, such as meat products, bread and bakery products, and cheese. Our analyses were adjusted for total energy intake and therefore the stronger associations in men might be due to the higher salt intake relative to total energy intake. However, regardless of the magnitude of the relationship, the associations were in similar direction in both men and women.”

The underlying biological mechanisms for this link remain uncertain. The authors state:

“The association between salt intake and obesity is still very unclear, and there are no waterproof explanations for the differences between sexes nor for the phenomenon in general. Research data is still very limited, but possible biological explanations have included changes in the secretion of satiety hormones as a result of long-term exposure to high salt intake. High salt intake may also act as a proxy for nutrition quality as a whole—overconsumption of food giving high levels of sodium and increasing the risk of obesity, possibly reflecting overconsumption of ultra-processed, high-sodium foods.”

Further investigation is required to better understand the relationship between sodium intake and obesity, including studies examining satiety signalling, the gut microbiome, and body composition.

Public Health Implications and the Role of the Food Industry

The researchers emphasise that reducing sodium intake should not rest solely on individuals. They argue for a systemic approach involving the food industry:

“In our view, the food industry plays a significant role in reducing the population’s sodium intake, as the majority of food consumption comes from sources other than unprocessed primary production. It is important to pay attention to how salty commonly consumed daily foods are, as these account for a large proportion of the daily sodium intake. Of course, general changes in the food environment also play a role, such as whether food is prepared at home or consumed in restaurants or as takeaway food.”

Conclusion

The study provides compelling evidence linking high sodium consumption—measured through both diet and urine samples—with an increased likelihood of general and abdominal obesity. These findings highlight the urgent need for further research and broader societal changes, particularly in food production and labelling, to help reduce sodium intake across populations. As the authors conclude:

“These results strengthen the evidence of an association between sodium intake and obesity, with similar findings observed for both dietary sodium and urine sodium concentration. It is important to gain more understanding about the biological mechanism of the relationship.”