Obesity
is a gateway disease
Which are the factors contributing to obesity?

Which are the factors contributing to obesity?

Which are the factors contributing to obesity?

Obesity is a disease with many contributing factors, including genetics, behavior, environment, medical factors, central nervous system (CNS) pathways, and peripheral signals.1-3  The below factors have been suggested to contribute to the obesity epidemic (Table 1).

Category

Factor

Potential mechanisms

Effects on energy balance

 Genetic2,4,5

Variations in BMI
Changes in genes responsible for weight and / or metabolism (epigenetics, deletions, single nucleotide polymorphisms)

Variable

↑ Energy intake and variable energy expenditure

 Behavioral2,6-8

Diet, inactivity, emotional factors

Multiple behavioral mechanisms

↑ Energy intake and variable energy expenditure

Lack of sleep

Multiple hormonal mechanisms: mostly leptin - and ghrelin - induced changes in appetite

↑ Energy intake and variable energy expenditure

Smoking cessation

Behavioral effect

↑ Energy intake and
↓ Energy expenditure

Environmental2,4,6,7,9

Access to/affordability of food, socioeconomic status, stress, physical environment, endocrine disruptors, gut microbiome

Multiple behavioral mechanisms

↑ Energy intake and variable energy expenditure

Medical1,2,10-13 

Pharmaceuticals such as corticosteroids and certain psychiatric drugs

Variable

↑ Energy intake and
↓ Energy expenditure

Diseases and conditions such as Polycystic Ovarian Syndrome (PCOS), Cushing’s syndrome, hypothyroidism, pregnancy-related weight gain, menopause, low testosterone

Variable

↑ Energy intake and variable energy expenditure

 CNS pathways3,13

Homeostatic and reward system pathways

Energy regulation in hypothalamus, dopamine reward system

↑ Energy intake and variable energy expenditure

Peripheral signals2,3

Hormones and gastrointestinal peptides [insulin, leptin, ghrelin, glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), amylin, peptide YY (PYY)]

Mostly leptin - and ghrelin - induced changes in appetite

Variable

BMI=Body mass index, CCK=Cholecystokinin, CNS=Central nervous system,
GLP-1=Glucagon-like peptide 1, PCOS=Polycystic ovarian syndrome, PYY=Peptide YY   

References

1. Jensen MD. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2012:1409-1417.

2. Cizza G et al J Endocrinol Invest. 2012;35:1-14.

3. Volkow ND et al. Obes Rev. 2013;14(1):2-18.

4. Nguyen DM et al. Gastroenterol Clin North Am. 2010;39:1-7.

5. Hjelmborg J et al. Obesity 2008;16:847-852.

6. Ahima RS. J Clin Invest. 2011;121:2076-2079.

7. Puhl RM et al. Am J Public Health. 2010;100:1019-1028.

8. Mackay DF et al. BMC Public Health. 2013;13:348.

9. Kushner RF et al. Psychiatr Clin North Am. 2011;34:797-812.

10. Robertson A et al. http://ec.europa.eu/health/ph_determinants/life_style/nutrition/documents/ev20081028_rep_en.pdf. Accessed 15 August 2016.

11. Gunderson EP. Obstet Gynecol Clin North Am. 2009;36:317- ix.

12. Wang C et al. Diabetes Care. 2011;34:1669-1675.

13. Schwartz MW et al. Nature. 2000;404:661-671.

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