Genes and Weight

It's certainly true that genes have an impact on body weight. Learn more below.
Genes and Weight

It is certainly true that the genes a person is born with have an impact on body weight. Research suggests that the impact is the result of ongoing interactions between the persons environment and individual genetic makeup. Studies indicate that 40-70% of the difference between individuals with respect to body fatness can be attributed to genetics.1

However, it is important to recognize that, except in very rare cases, the genes that impact body weight do not directly cause obesity. Rather, genetic makeup influences the susceptibility to weight gain when the person lives in an environment that supports eating calories in excess and/or limiting physical activity.1

Over the last decade, our understanding of the role of genetics in determining body weight has significantly advanced. As the story has unfolded, the complexities have increased exponentially. Current findings suggest that, with only rare exceptions of a single gene mutation that results in severe morbid obesity, there are numerous genes (i.e., possibly several hundred) that affect susceptibility to overweight. Moreover, the various genes interact with one another to further influence vulnerability.2

Birth Weight Links to Obesity
Susceptibility to obesity does not appear to be limited to genes alone. There is increasing research that suggests that the environment to which a fetus is exposed during pregnancy impacts weight later in life. Indeed, many studies have found direct links between both high and low birth weights and a greater likelihood for overweight and obesity years later.3

Genetics and Behaviors
To add yet more complexity, newer research suggests that the role of genetics expands beyond the ultimate weight that shows on the bathroom scale. It is now widely recognized that the influence of genes extends to weight-related behaviors as well.4 Food preferences, dietary patterns and exercise behaviors are all likely to be determined, in part, by genes.

While genes play a part in determining susceptibility to overweight, they do not appear to play a role in the weight fluctuations or the typical weight gain experienced during the middle adult years.5

The bottom line is that biology is not destiny. While genes influence susceptibility to overweight and have an influence on weight-related behaviors, the genes cannot be expressed unless the environment supports them.

This content is reviewed regularly. Last updated November 12, 2012.

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Other Science Library Topics:

1 Herrera BM, Keildson S, Lindgren CM. Genetics and epigenetics of obesity. Maturitas. 2011 May;69(1):41-9. Epub 2011 Apr 3.

2 Rankinen T, Zuberi A, Chagnon YC, et al. The human obesity gene map: the 2005 update. Obesity (Silver Spring). 2006 Apr;14(4):529-644.

3 Yu ZB, Han SP, Zhu GZ, et al. Birth weight and subsequent risk of obesity: a systematic review and meta-analysis. Obes Rev. 2011 Mar 28. doi: 10.1111/j.1467-789X.2011.00867.x. [Epub ahead of print] .

4de Krom M, Bauer F, Collier D, Adan RA, la Fleur SE. Genetic variation and effects on human eating behavior. Annu Rev Nutr. 2009;29:283-304.

5Coady SA, Jaquish CE, Fabsitz RR, Larson MG, Cupples LA, Myers RH. Genetic variability of adult body mass index: a longitudinal assessment in framingham families. Obes Res. 2002 Jul;10(7):675-81.

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