What Is Obesity ?

Obese people straining in their clothes.
photo by cocparisienne, c/o Pixabay.

Obesity is probably now the most serious health issue for billions of people in the developed and developing countries. It is in fact a global crisis (Flegal et al., 1998; Kelly et al., 2008). To be honest more people on the planet are now overweight or obese than they are underweight. It was the case that the occurrence of being below- or underweight was more than twice the incidence of obesity (Collaboration, 2016). Who can forget the appalling images of malnourished people in a starving Africa for example back in the 60s and 70s. That seems to have come off our screens although famine still stalks the lands throughout the planet.

We probably all know what obesity is. It is the excess accumulation of fat in the form of triglycerides by the body in what is called adipose tissue.

Such an accumulation produces poor health. Over consumption of high-calorie foods coupled with a sedentary lifestyle are the two main factors contributing to the occurrence of obesity (Al-Kloub & Froelicher, 2009). 

A large number of articles in nutrition particularly often cite obesity as one of the risk factors and this does not discriminate with age or gender. Recent data now reports over 30% adults and 16.9% children in the United States for example suffer from the debilitating impact  of obesity with the estimated healthcare cost  now somewhere between 100 to 200 million dollars annually (Finkelstein et al., 2005; Ogden et al., 2012). In China, about 200 million people and 12.8% children are obese or overweight with the associated medical cost reaching around 3 billion dollars every year (Zhao et al., 2008; Yu et al., 2012).

The Impact Of Obesity On Health.

Obesity is also known as a key risk factor of metabolic syndrome, type-2 diabetes, hypertension (high blood pressure), hyperlipidaemia, nonalcoholic fatty liver disease or steatohepatitis (NAFLD), cardiovascular and cerebrovascular diseases, stroke and even some cancers (Reaven et al., 2004; Flegal et al., 2005, 2007). A number of articles on this web-site discuss obesity and both the products and methods available to reduce weight loss and its management.

The general biochemistry behind obesity takes the following form. Our adipose tissue is designed primarily for storing fat (Kim et al., 2016). This tissue expands as we acquire more fat. It is mainly composed of cells called adipocytes.

Adipose tissue expansion is caused by two processes of hypertrophy and hyperplasia. In the progression of obesity, hypertrophy precedes hyperplasia.

Adipogenesis is the process where cells known as preadipocytes differentiate into lipid-laden adipocytes. It occurs in several stages which involve:-

  • preadipocyte cell proliferation,
  • differentiation
  • lipid accumulation

The transcription factors such as peroxisome proliferator activated receptor gamma (PPARγ) and CCAAT/enhancer binding proteins (C/EBPs) regulates this process (Kim et al., 2015a; Kim et al., 2015b).

Lipogenesis is the process of triglyceride (TG) synthesis, which requires enzymes including acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) (Sung et al., 2011). Conversely, in the process of breaking down fat, known as lipolysis, adipose triglyceride lipase (ATGL) and hormone‐sensitive lipase (HSL) are required (Kim et al., 2016). TG is broken down into fatty acids, which then can undergo β‐oxidation, mainly in the liver. These lipid metabolic pathways demonstrate the possibility that obesity could be ameliorated by the regulating processes such as adipogenesis, lipogenesis, lipolysis and β‐oxidation. 

References

Al‐Kloub, M. I., & Froelicher, E. S.(2009). Factors contributing to adolescent obesitySaudi Medical Journal30(6), pp. 737749.

Collaboration, N. C. D. R. F. (2016). Trends in adult body‐mass index in 200 countries from 1975 to 2014: A pooled analysis of 1698 population‐based measurement studies with 19.2 million participantsLancet387(10026), pp. 13771396https://doi.org/10.1016/S0140-6736(16)30054-X

Finkelstein, E., Fiebelkorn, I.C., Wang, G. (2005) The costs of obesity among full-time employees. Am. J. Health Promot. 20(1) pp.4551

Flegal, K. M., Carroll, M. D., Kuczmarski, R. J., & Johnson, C. L. (1998). Overweight and obesity in the United States: prevalence and trends, 1960–1994. International Journal of Obesity22(1), pp. 39-47 (Article). 

Flegal, K.M., Graubard, B.I., Williamson, D.F., Gail, M.H. (2005) Excess deaths associated with underweight, overweight, and obesity. J. Am. Med. Assoc. 293(15) pp. 18617

Flegal, K.M., Graubard, B.I., Williamson, D.F., Gail, M.H. (2007) Cause-specific excess deaths associated with underweight, overweight, and obesity. J. Am. Med. Assoc. 298(17) pp. 202837

Kelly, T., Yang, W., Chen, C. S., Reynolds, K., & He, J. (2008). Global burden of obesity in 2005 and projections to 2030. International Journal of Obesity32(9), pp. 1431-1437 (Article). 

Kim, J. H.Kim, O. K.Yoon, H. G.Park, J.You, Y.Kim, K., … Jun, W.(2016). Anti‐obesity effect of extract from fermented Curcuma longa L. through regulation of adipogenesis and lipolysis pathway in high‐fat diet‐induced obese ratsFood and Nutrition Research6030428 (Article).  

Kim, K. N., Kang, M. C., Kang, N., Kim, S. Y., Hyun, C. G., Roh, S. W., … Ahn, G. (2015a). 2, 4, 6‐Trihydroxybenzaldehyde, a potential anti‐obesity treatment, suppressed adipocyte differentiation in 3T3‐L1 cells and fat accumulation induced by high‐fat diet in C57BL/6 miceEnvironmental Toxicology and Pharmacology39(2), pp. 962968https://doi.org/10.1016/j.etap.2015.02.007

Kim, M., Park, J. E., Song, S. B., & Cha, Y. S. (2015b). Effects of black adzuki bean (Vigna angularis) extract on proliferation and differentiation of 3T3‐L1 preadipocytes into mature adipocytesNutrients7(1), pp. 277292https://doi.org/10.3390/nu7010277

Ogden, C.L., Carroll, M.D., Kit, B.K., Flegal, K.M. (2012) Prevalence of obesity among adults: United States. NCHS Data Brief 2013 pp. 18

Sung, J. H., Chon, J. W., Lee, M. A., Park, J. K., Woo, J. T., & Park, Y. K.(2011). The anti‐obesity effect of Lethariella cladonioides in 3T3‐L1 cells and obese miceNutrition Research and Practice, 5(6), pp. 503510https://doi.org/10.4162/nrp.2011.5.6.503

Yu, Z., Han, S., Chu, J., Xu, Z., Zhu, C., Guo, X. (2012) Trends in overweight and obesity among children and adolescents in China from 1981 to 2010: a meta-analysis. PLoS One 7(12):e51949.

Zhao, W., Zhai, Y., Hu, J., Wang, J., Yang, Z., Kong, L., Chen, C. (2008) Economic burden of obesity-related chronic diseases in Mainland China. Obes. Rev. 9(s1)  pp. 627

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