Country of Birth, Marital Status, and Sex are Strong Predictors of Obesity

Computer illustration of the abdomen before (left) and after (right) a gastric bypass.
Obesity is caused by an imbalance of calories consumed vs calories expended, but researchers say there are additional risk factors at work as well.

Country of birth, marital status, and sex are among the strongest individual predictors of people who develop a high body mass index (BMI) or obesity, according to a study in BMC Endocrine Disorders.

An ongoing, prospective, nonrandomized cohort Bariatric surgery Substitution and Nutrition (BASUN) study initially included 1127 individuals with a BMI of 35 kg/m2 or higher. These individuals were referred for medical or surgical treatment for obesity in Region Västra Götaland, Sweden, from May 2015 to November 2017.

Investigators used the machine learning algorithm random forest to examine the importance of more than 100 clinical variables as predictors for BMI. The variables were also grouped into 15 clinically similar domains, including socioeconomic status, age/sex, lifestyle, habits, and others.

A total of 971 individuals were included in the final analysis: medical treatment (n = 382; mean [SD] age 47.6 [14.2] years; 27.2% male); Roux-en-Y gastric bypass (n = 388; mean [SD] age 42.03 [11.3]; 22.4% male); and sleeve gastrectomy (n = 201; mean [SD] age 40.89 [11.0]; 24.4% male). Of this cohort, 156 individuals chose not to continue to treatment.

The 10 individual variables that had the strongest predictive value for BMI, in order of decreasing strength, were country of birth, marital status, sex, calcium levels, age, thyroid stimulating hormone (TSH) level, glycated hemoglobin (HbA1c), Alcohol Use Disorders Identification Test scores, binge eating (according to the Questionnaire on Eating and Weight Patterns-Revised, and triglyceride levels.

The strongest clinical domains for predicting high BMI and obesity were socioeconomic status; age/sex; biomarkers for TSH, hemoglobin, calcium, and others; lifestyle/habits; biomarkers for cardiovascular disease and diabetes; and potential anxiety and depression.

Among several study limitations, the enrolled individuals were referred and accepted for treatment of obesity, and this population may be different from the general overweight population. Also, the study is largely based on self-reported data and individuals with the most severe psychiatric disorders may not answer the questionnaires, and those who do not succeed with their treatment might not report back during the follow-up. Furthermore, information on income or employment status was not included, and an inclusion criterion was that participants could understand Swedish.

“These results confirm previously suggested associations and advocate prospective studies to examine the value of better characterization of patients eligible for obesity treatment, and consequently to evaluate the treatment effects in groups of patients,” stated the researchers.

Disclosure: The study was financed by grants from the Novo Nordisk Foundation and others. One of the study authors declared affiliations with pharmaceutical companies. Please see the original reference for a full list of author disclosures.


Höskuldsdóttir G, Engström M, Rawshani A, et al. The BAriatic surgery SUbstitution and nutrition (BASUN) population: a data-driven exploration of predictors for obesity. BMC Endocr Disord. 2021;21(1):183. doi:10.1186/s12902-021-00849-9